CODES

ADOPTS WITH AMENDMENTS:

International Residential Code 2015 (IRC 2015)

Chapter 1 Scope and Administration

Chapter 2 Definitions

Chapter 3 Building Planning

Chapter 4 Foundations

Chapter 5 Floors

Chapter 6 Wall Construction

Chapter 7 Wall Covering

Chapter 8 Roof-Ceiling Construction

Chapter 9 Roof Assemblies

Chapter 10 Chimneys and Fireplaces

Chapter 11 [RE] Energy Efficiency

Chapter 12 Mechanical Administration

Chapter 13 General Mechanical System Requirements

Chapter 14 Heating and Cooling Equipment and Appliances

Chapter 15 Exhaust Systems

Chapter 16 Duct Systems

Chapter 17 Combustion Air

Chapter 18 Chimneys and Vents

Chapter 19 Special Appliances, Equipment and Systems

Chapter 20 Boilers and Water Heaters

Chapter 21 Hydronic Piping

Chapter 22 Special Piping and Storage Systems

Chapter 23 Solar Thermal Energy Systems

Chapter 24 Fuel Gas

Chapter 25 Plumbing Administration

Chapter 26 General Plumbing Requirements

Chapter 27 Plumbing Fixtures

Chapter 28 Water Heaters

Chapter 29 Water Supply and Distribution

Chapter 30 Sanitary Drainage

Chapter 31 Vents

Chapter 32 Traps

Chapter 33 Storm Drainage

Chapter 34 General Requirements

Chapter 35 Electrical Definitions

Chapter 36 Services

Chapter 37 Branch Circuit and Feeder Requirements

Chapter 38 Wiring Methods

Chapter 39 Power and Lighting Distribution

Chapter 40 Devices and Luminaries

Chapter 41 Appliance Installation

Chapter 42 Swimming Pools

Chapter 43 Class 2 Remote-Control, Signaling and Power-Limited Circuits

Chapter 44 Referenced Standards

Appendix A Sizing and Capacities of Gas Piping

Appendix B Sizing of Venting Systems serving Appliances Equipped with Draft Hoods, Category I Appliances, and Appliances Listed for Use with Type B Vents

Appendix C Exit Terminals of Mechanical Draft and Direct-Vent Venting Systems

Appendix D Recommended Procedure for Safety Inspection of an Existing Appliance Installation

Appendix E Manufactured Housing used as Dwellings

Appendix F Passive Radon Gas Controls

Appendix G Piping Standards for Various Applications

Appendix J Existing Building and Structures

Appendix K Sound Transmission

Appendix N VENTING METHODS

Appendix O Automatic Vehicular Gates

Appendix P Sizing of Water Piping System

Appendix R Light Straw-Clay Construction

Appendix S Strawbale Construction

The provisions of this chapter shall control the design and construction of the roof-ceiling system for buildings.
Roof and ceiling construction shall be capable of accommodating all loads imposed in accordance with Section R301 and of transmitting the resulting loads to the supporting structural elements.
In areas where expansive or collapsible soils are known to exist, all dwellings shall have a controlled method of water disposal from roofs that will collect and discharge roof drainage to the ground surface not less than 5 feet (1524 mm) from foundation walls or to an approved drainage system.
Wood and wood-based products used for load-supporting purposes shall conform to the applicable provisions of this section.
Sawn lumber shall be identified by a grade mark of an accredited lumber grading or inspection agency and have design values certified by an accreditation body that complies with DOC PS 20. In lieu of a grade mark, a certificate of inspection issued by a lumber grading or inspection agency meeting the requirements of this section shall be accepted.
Approved end-jointed lumber identified by a grade mark conforming to Section R802.1 shall be permitted to be used interchangeably with solid-sawn members of the same species and grade. End-jointed lumber used in an assembly required elsewhere in this code to have a fire-resistance rating shall have the designation "Heat-Resistant Adhesive" or "HRA" included in its grade mark.
Glued laminated timbers shall be manufactured and identified as required in ANSI/AITC A190.1 and ASTM D3737.
Structural log members shall comply with the provisions of ICC 400.
Structural capacities for structural composite lumber shall be established and monitored in accordance with ASTM D5456.
Fire-retardanttreated wood (FRTW) is any wood product that, when impregnated with chemicals by a pressure process or other means during manufacture, shall have, when tested in accordance with ASTM E84 or UL 723, a listed flame spread index of 25 or less and shows no evidence of significant progressive combustion where the test is continued for an additional 20-minute period. In addition, the flame front shall not progress more than 10.5 feet (3200 mm) beyond the center line of the burners at any time during the test.
For wood products impregnated with chemicals by a pressure process, the process shall be performed in closed vessels under pressures not less than 50 pounds per square inch gauge (psig) (344.7 kPa).
For wood products produced by other means during manufacture the treatment shall be an integral part of the manufacturing process of the wood product. The treatment shall provide permanent protection to all surfaces of the wood product.
For wood products produced by other means during manufacture, other than a pressure process, all sides of the wood product shall be tested in accordance with and produce the results required in Section R802.1.3. Testing of only the front and back faces of wood structural panels shall be permitted.
Fire-retardant-treated lumber and wood structural panels shall be labeled. The label shall contain:
  1. The identification mark of an approved agency in accordance with Section 1703.5 of the International Building Code.
  2. Identification of the treating manufacturer.
  3. The name of the fire-retardant treatment.
  4. The species of wood treated.
  5. Flame spread index and smoke-developed index.
  6. Method of drying after treatment.
  7. Conformance to applicable standards in accordance with Sections R802.1.5.5 through R802.1.5.10.
  8. For FRTW exposed to weather, or a damp or wet location, the words "No increase in the listed classification when subjected to the Standard Rain Test" (ASTM D2898).
Design values for untreated lumber and wood structural panels as specified in Section R802.1 shall be adjusted for fire-retardanttreated wood. Adjustments to design values shall be based upon an approved method of investigation that takes into consideration the effects of the anticipated temperature and humidity to which the fire-retardanttreated wood will be subjected, the type of treatment and redrying procedures.
The effect of treatment and the method of redrying after treatment, and exposure to high temperatures and high humidities on the flexure properties of fire-retardant-treated softwood plywood shall be determined in accordance with ASTM D5516. The test data developed by ASTM D5516 shall be used to develop adjustment factors, maximum loads and spans, or both for untreated plywood design values in accordance with ASTM D6305. Each manufacturer shall publish the allowable maximum loads and spans for service as floor and roof sheathing for their treatment.
For each species of wood treated, the effect of the treatment and the method of redrying after treatment and exposure to high temperatures and high humidities on the allowable design properties of fire-retardant-treated lumber shall be determined in accordance with ASTM D5664. The test data developed by ASTM D5664 shall be used to develop modification factors for use at or near room temperature and at elevated temperatures and humidity in accordance with ASTM D6841. Each manufacturer shall publish the modification factors for service at temperatures of not less than 80°F (27°C) and for roof framing. The roof framing modification factors shall take into consideration the climatological location.
Where fire-retardant-treated wood is exposed to weather or damp or wet locations, it shall be identified as "Exterior" to indicate there is not an increase in the listed flame spread index as defined in Section R802.1.5 when subjected to ASTM D2898.
Interior fire-retardant-treated wood shall have a moisture content of not over 28 percent when tested in accordance with ASTM D3201 procedures at 92-percent relative humidity. Interior fire-retardant-treated wood shall be tested in accordance with Section R802.1.5.6 or R802.1.5.7. Interior fire-retardant-treated wood designated as Type A shall be tested in accordance with the provisions of this section.
Fire-retardant-treated wood shall be dried to a moisture content of 19 percent or less for lumber and 15 percent or less for wood structural panels before use. For wood kiln dried after treatment (KDAT) the kiln temperatures shall not exceed those used in kiln drying the lumber and plywood submitted for the tests described in Section R802.1.5.6 for plywood and R802.1.5.7 for lumber.
Cross-laminated timber shall be manufactured and identified as required by ANSI/APA PRG 320.
Engineered wood rim boards shall conform to ANSI/APA PRR 410 or shall be evaluated in accordance with ASTM D7672. Structural capacities shall be in accordance with ANSI/APA PRR 410 or established in accordance with ASTM D7672. Rim boards conforming to ANSI/APA PRR 410 shall be marked in accordance with that standard.
The framing details required in Section R802 apply to roofs having a minimum slope of three units vertical in 12 units horizontal (25-percent slope) or greater. Roof-ceilings shall be designed and constructed in accordance with the provisions of this chapter and Figures R606.11(1), R606.11(2) and R606.11(3) or in accordance with AWC NDS. Components of roof-ceilings shall be fastened in accordance with Table R602.3(1).
Rafters shall be framed not more than 1½-inches (38 mm) offset from each other to ridge board or directly opposite from each other with a gusset plate as a tie. Ridge board shall be not less than 1-inch (25 mm) nominal thickness and not less in depth than the cut end of the rafter. At valleys and hips there shall be a valley or hip rafter not less than 2-inch (51 mm) nominal thickness and not less in depth than the cut end of the rafter. Hip and valley rafters shall be supported at the ridge by a brace to a bearing partition or be designed to carry and distribute the specific load at that point. Where the roof pitch is less than three units vertical in 12 units horizontal (25-percent slope), structural members that support rafters and ceiling joists, such as ridge beams, hips and valleys, shall be designed as beams.
Ceiling joists and rafters shall be nailed to each other in accordance with Table R802.5.1(9), and the rafter shall be nailed to the top wall plate in accordance with Table R602.3(1). Ceiling joists shall be continuous or securely joined in accordance with Table R802.5.1(9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building where such joists are parallel to the rafters.

     Where ceiling joists are not connected to the rafters at the top wall plate, joists connected higher in the attic shall be installed as rafter ties, or rafter ties shall be installed to provide a continuous tie. Where ceiling joists are not parallel to rafters, rafter ties shall be installed. Rafter ties shall be not less than 2 inches by 4 inches (51 mm by 102 mm) (nominal), installed in accordance with the connection requirements in Table R802.5.1(9), or connections of equivalent capacities shall be provided. Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice.

     Collar ties or ridge straps to resist wind uplift shall be connected in the upper third of the attic space in accordance with Table R602.3(1).

     Collar ties shall be not less than 1 inch by 4 inches (25 mm by 102 mm) (nominal), spaced not more than 4 feet (1219 mm) on center.

TABLE R802.5.1(9)
RAFTER/CEILING JOIST HEEL JOINT CONNECTIONSa, b, c, d, e, f, h
RAFTER
SLOPE
RAFTER
SPACING
(inches)
GROUND SNOW LOAD (psf)
20g 30 50 70
Roof span (feet)
12 20 28 36 12 20 28 36 12 20 28 36 12 20 28 36
Required number of 16d common nailsa, b per heel joint splicesc, d, e, f
3:12 12 4 6 8 10 4 6 8 11 5 8 12 15 6 11 15 20
16 5 8 10 13 5 8 11 14 6 11 15 20 8 14 20 26
24 7 11 15 19 7 11 16 21 9 16 23 30 12 21 30 39
4:12 12 3 5 6 8 3 5 6 8 4 6 9 11 5 8 12 15
16 4 6 8 10 4 6 8 11 5 8 12 15 6 11 15 20
24 5 8 12 15 5 9 12 16 7 12 17 22 9 16 23 29
5:12 12 3 4 5 6 3 4 5 7 3 5 7 9 4 7 9 12
16 3 5 6 8 3 5 7 9 4 7 9 12 5 9 12 16
24 4 7 9 12 4 7 10 13 6 10 14 18 7 13 18 23
7:12 12 3 4 4 5 3 3 4 5 3 4 5 7 3 5 7 9
16 3 4 5 6 3 4 5 6 3 5 7 9 4 6 9 11
24 3 5 7 9 3 5 7 9 4 7 10 13 5 9 13 17
9:12 12 3 3 4 4 3 3 3 4 3 3 4 5 3 4 5 7
16 3 4 4 5 3 3 4 5 3 4 5 7 3 5 7 9
24 3 4 6 7 3 4 6 7 3 6 8 10 4 7 10 13
12:12 12 3 3 3 3 3 3 3 3 3 3 3 4 3 3 4 5
16 3 3 4 4 3 3 3 4 3 3 4 5 3 4 5 7
24 3 4 4 5 3 3 4 6 3 4 6 8 3 6 8 10
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. 40d box nails shall be permitted to be substituted for 16d common nails.
  2. Nailing requirements shall be permitted to be reduced 25 percent if nails are clinched.
  3. Heel joint connections are not required where the ridge is supported by a load-bearing wall, header or ridge beam.
  4. Where intermediate support of the rafter is provided by vertical struts or purlins to a load-bearing wall, the tabulated heel joint connection requirements shall be permitted to be reduced proportionally to the reduction in span.
  5. Equivalent nailing patterns are required for ceiling joist to ceiling joist lap splices.
  6. Where rafter ties are substituted for ceiling joists, the heel joint connection requirement shall be taken as the tabulated heel joint connection requirement for two-thirds of the actual rafter slope.
  7. Applies to roof live load of 20 psf or less.
  8. Tabulated heel joint connection requirements assume that ceiling joists or rafter ties are located at the bottom of the attic space. Where ceiling joists or rafter ties are located higher in the attic, heel joint connection requirements shall be increased by the following factors:

    HC/HR Heel Joint Connection Adjustment Factor
    1/3
    1/4
    1/5
    1/6
    1/10 or less
    1.5
    1.33
    1.25
    1.2
    1.11

    where:
    HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
    HR = Height of roof ridge measured vertically above the top of the rafter support walls.
Ends of ceiling joists shall be lapped not less than 3 inches (76 mm) or butted over bearing partitions or beams and toenailed to the bearing member. Where ceiling joists are used to provide resistance to rafter thrust, lapped joists shall be nailed together in accordance with Table R802.5.1(9) and butted joists shall be tied together in a manner to resist such thrust. Joists that do not resist thrust shall be permitted to be nailed in accordance with Table R602.3(1).
Blocking shall be a minimum of utility grade lumber.
Spans for ceiling joists shall be in accordance with Tables R802.4(1) and R802.4(2). For other grades and species and for other loading conditions, refer to the AWC STJR.

TABLE R802.4(1)
CEILING JOIST SPANS FOR COMMON LUMBER SPECIES
(Uninhabitable attics without storage, live load= 10 psf, L/Δ = 240)
CEILING JOIST
SPACING (inches)
SPECIES AND GRADE DEAD LOAD = 5 psf
2 x 4
2 x 6
2 x 8
2 x 10
Maximum ceiling joist spans
(feet - inches) (feet - inches) (feet - inches) (feet - inches)
12 Douglas fir-larch                     SS
13-2 20-8 Note a Note a
Douglas fir-larch                     #1
12-8 19-11 Note a Note a
Douglas fir-larch                     #2
12-5 19-6 25-8 Note a
Douglas fir-larch                     #3
11-1 16-3 20-7 25-2
Hem-fir                                    SS
12-5 19-6 25-8 Note a
Hem-fir                                    #1
12-2 19-1 25-2 Note a
Hem-fir                                    #2
11-7 18-2 24-0 Note a
Hem-fir                                    #3
10-10 15-10 20-1 24-6
Southern pine                         SS
12-11 20-3 Note a
Note a
Southern pine                         #1
2-5 19-6 25-8 Note a
Southern pine                         #2
11-10 18-8 24-7 Note a
Southern pine                         #3
10-1 14-11 18-9 22-9
Spruce-pine-fir                        SS
12-2 19-1 25-2 Note a
Spruce-pine-fir                        #1
11-10 18-8 24-7 Note a
Spruce-pine-fir                        #2
11-10 18-8 24-7 Note a
Spruce-pine-fir                        #3
10-10 15-10 20-1 24-6
16 Douglas fir-larch                     SS
11-11 18-9 24-8 Note a
Douglas fir-larch                     #1
11-6 18-1 23-10 Note a
Douglas fir-larch                     #2 11-3 17-8 23-4 Note a
Douglas fir-larch                     #3 9-7 14-1 17-10 21-9
Hem-fir                                    SS
11-3 17-8 23-4 Note a
Hem-fir                                    #1 11-0 17-4 22-10 Note a
Hem-fir                                    #2 10-6 16-6 21-9 Note a
Hem-fir                                    #3 9-5 13-9 17-5 21-3
Southern pine                         SS
11-9 18-5 24-3 Note a
Southern pine                         #1 11-3 17-8 23-10 Note a
Southern pine                         #2 10-9 16-11 21-7 25-7
Southern pine                         #3 8-9 12-11 16-3 19-9
Spruce-pine-fir                        SS
11-0 17-4 22-10 Note a
Spruce-pine-fir                        #1 10-9 16-11 22-4 Note a
Spruce-pine-fir                        #2 10-9 16-11 22-4 Note a
Spruce-pine-fir                        #3 9-5 13-9 17-5 21-3
19.2 Douglas fir-larch                     SS
11-3 17-8 23-3 Note a
Douglas fir-larch                     #1 10-10 17-0 22-5 Note a
Douglas fir-larch                     #2 10-7 16-8 21-4 26-0
Douglas fir-larch                     #3 8-9 12-10 16-3 19-10
Hem-fir                                    SS
10-7 16-8 21-11 Note a
Hem-fir                                    #1 10-4 16-4 21-6 Note a
Hem-fir                                    #2 9-11 15-7 20-6 25-3
Hem-fir                                    #3 8-7 12-6 15-10 19-5
Southern pine                         SS
11-0 17-4 22-10 Note a
Southern pine                         #1 10-7 16-8 22-0 Note a
Southern pine                         #2 10-2 15-7 19-8 23-5
Southern pine                         #3 8-0 11-9 14-10 18-0
Spruce-pine-fir                        SS
10-4 16-4 21-6 Note a
Spruce-pine-fir                        #1 10-2 15-11 21-0 25-8
Spruce-pine-fir                        #2 10-2 15-11 21-0 25-8
Spruce-pine-fir                        #3 8-7 12-6 15-10 19-5
24 Douglas fir-larch                     SS
10-5 16-4 21-7 Note a
Douglas fir-larch                     #1 10-0 15-9 20-1 24-6
Douglas fir-larch                     #2 9-10 15-0 19-1 23-3
Douglas fir-larch                     #3 7-10 11-6 14-7 17-9
Hem-fir                                    SS
9-10 15-6 20-5 Note a
Hem-fir                                    #1 9-8 15-2 19-10 24-3
Hem-fir                                    #2 9-2 14-5 18-6 22-7
Hem-fir                                    #3 7-8 11-2 14-2 17-4
Southern pine                         SS
10-3 16-1 21-2 Note a
Southern pine                         #1 9-10 15-6 20-5 24-0
Southern pine                         #2 9-3 13-11 17-7 20-11
Southern pine                         #3 7-2 10-6 13-3 16-1
Spruce-pine-fir                        SS
9-8 15-2 19-11 25-5
Spruce-pine-fir                        #1 9-5 14-9 18-9 22-11
Spruce-pine-fir                        #2 9-5 14-9 18-9 22-11
Spruce-pine-fir                        #3 7-8 11-2 14-2 17-4
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
a. Span exceeds 26 feet in length



TABLE R802.4(2)
CEILING JOIST SPANS FOR COMMON LUMBER SPECIES
(Uninhabitable attics with limited storage, live load = 20 psf, L/Δ = 240)
CEILING JOIST
SPACING (inches)
SPECIES AND GRADE DEAD LOAD = 5 psf
2 x 4
2 x 6
2 x 8
2 x 10
Maximum ceiling joist spans
(feet - inches) (feet - inches) (feet - inches) (feet - inches)
12 Douglas fir-larch                     SS
10-5 16-4 21-7 Note a
Douglas fir-larch                     #1
10-0 15-9 20-1 24-6
Douglas fir-larch                     #2
9-10 15-0 19-1 23-3
Douglas fir-larch                     #3
7-10 11-6 14-7 17-9
Hem-fir                                    SS
9-10 15-6 20-5 Note a
Hem-fir                                    #1
9-8 15-2 19-10 24-3
Hem-fir                                    #2
9-2 14-5 18-6 22-7
Hem-fir                                    #3
7-8 11-2 14-2 17-4
Southern pine                         SS
10-3 16-1 21-2 Note a
Southern pine                         #1
9-10 15-6 20-5 24-0
Southern pine                         #2
9-3 13-11 17-7 20-11
Southern pine                         #3
7-2 10-6 13-3 16-1
Spruce-pine-fir                        SS
9-8 15-2 19-11 25-5
Spruce-pine-fir                        #1
9-5 14-9 18-9 22-11
Spruce-pine-fir                        #2
9-5 14-9 18-9 22-11
Spruce-pine-fir                        #3
7-8 11-2 14-2 17-4
16 Douglas fir-larch                     SS
9-6 14-11 19-7 25-0
Douglas fir-larch                     #1
9-1 13-9 17-5 21-3
Douglas fir-larch                     #2 8-11 13-0 16-6 20-2
Douglas fir-larch                     #3 6-10 9-11 12-7 15-5
Hem-fir                                    SS
8-11 14-1 18-6 23-8
Hem-fir                                    #1 8-9 13-7 17-2 21-0
Hem-fir                                    #2 8-4 12-8 16-0 19-7
Hem-fir                                    #3 6-8 9-8 12-4 15-0
Southern pine                         SS
9-4 14-7 19-3 24-7
Southern pine                         #1 8-11 14-0 17-9 20-9
Southern pine                         #2 8-0 12-0 15-3 18-1
Southern pine                         #3 6-2 9-2 11-6 14-0
Spruce-pine-fir                        SS
8-9 13-9 18-1 23-1
Spruce-pine-fir                        #1 8-7 12-10 16-3 19-10
Spruce-pine-fir                        #2 8-7 12-10 16-3 19-10
Spruce-pine-fir                        #3 6-8 9-8 12-4 15-0
19.2 Douglas fir-larch                     SS
8-11 14-0 18-5 23-7
Douglas fir-larch                     #1 8-7 12-6 15-10 19-5
Douglas fir-larch                     #2 8-2 11-11 15-1 18-5
Douglas fir-larch                     #3 6-2 9-1 11-6 14-1
Hem-fir                                    SS
8-5 13-3 17-5 22-3
Hem-fir                                    #1 8-3 12-4 15-8 19-2
Hem-fir                                    #2 7-10 11-7 14-8 17-10
Hem-fir                                    #3 6-1 8-10 11-3 13-8
Southern pine                         SS
8-9 13-9 18-2 23-1
Southern pine                         #1 8-5 12-9 16-2 18-11
Southern pine                         #2 7-4 11-0 13-11 16-6
Southern pine                         #3 5-8 8-4 10-6 12-9
Spruce-pine-fir                        SS
8-3 12-11 17-1 21-8
Spruce-pine-fir                        #1 8-0 11-9 14-10 18-2
Spruce-pine-fir                        #2 8-0 11-9 14-10 18-2
Spruce-pine-fir                        #3 6-1 8-10 11-3 13-8
24 Douglas fir-larch                     SS
8-3 13-0 17-2 21-3
Douglas fir-larch                     #1 7-8 11-2 14-2 17-4
Douglas fir-larch                     #2 7-3 10-8 13-6 16-5
Douglas fir-larch                     #3 5-7 8-1 10-3 12-7
Hem-fir                                    SS
7-10 12-3 16-2 20-6
Hem-fir                                    #1 7-7 11-1 14-0 17-1
Hem-fir                                    #2 7-1 10-4 13-1 16-0
Hem-fir                                    #3 5-5 7-11 10-0 12-3
Southern pine                         SS
8-1 12-9 16-10 21-6
Southern pine                         #1 7-8 11-5 14-6 16-11
Southern pine                         #2 6-7 9-10 12-6 14-9
Southern pine                         #3 5-1 7-5 9-5 11-5
Spruce-pine-fir                        SS
7-8 12-0 15-10 19-5
Spruce-pine-fir                        #1 7-2 10-6 13-3 16-3
Spruce-pine-fir                        #2 7-2 10-6 13-3 16-3
Spruce-pine-fir                        #3 5-5 7-11 10-0 12-3
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
a. Span exceeds 26 feet in length
Spans for rafters shall be in accordance with Tables R802.5.1(1) through R802.5.1(8). For other grades and species and for other loading conditions, refer to the AWC STJR. The span of each rafter shall be measured along the horizontal projection of the rafter.

TABLE R802.5.1(1)
RAFTER SPANS FOR COMMON LUMBER SPECIES
(Roof live load = 20 psf, ceiling not attached to rafters, L/Δ = 180)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
11-6 18-0 23-9 Note b Note b 11-6 18-0 23-9 Note b
Note b
Douglas fir-larch                     #1
11-1 17-4 22-5 Note b Note b 10-6 15-4 19-5 23-9 Note b
Douglas fir-larch                     #2
10-10 16-10 21-4 26-0 Note b 10-0 14-7 18-5 22-6 26-0
Douglas fir-larch                     #3
8-9 12-10 16-3 19-10 23-0 7-7 11-1 14-1 17-2 19-11
Hem-fir                                    SS
10-10 17-0 22-5 Note b Note b 10-10 17-0 22-5 Note b Note b
Hem-fir                                    #1
10-7 16-8 22-0 Note b Note b 10-4 15-2 19-2 23-5 Note b
Hem-fir                                    #2
10-1 15-11 20-8 25-3 Note b 9-8 14-2 17-11 21-11 25-5
Hem-fir                                    #3
8-7 12-6 15-10 19-5 22-6 7-5 10-10 13-9 16-9 19-6
Southern pine                         SS
11-3 17-8 23-4 Note b Note b 11-3 17-8 23-4 Note b Note b
Southern pine                         #1
10-10 17-0 22-5 Note b Note b 10-6 15-8 19-10 23-2 Note b
Southern pine                         #2
10-4 15-7 19-8 23-5 Note b 9-0 13-6 17-1 20-3 23-10
Southern pine                         #3
8-0 11-9 14-10 18-0 21-4 6-11 10-2 12-10 15-7 18-6
Spruce-pine-fir                        SS
10-7 16-8 21-11 Note b Note b 10-7 16-8 21-9 Note b Note b
Spruce-pine-fir                        #1
10-4 16-3 21-0 25-8 Note b 9-10 14-4 18-2 22-3 25-9
Spruce-pine-fir                        #2
10-4 16-3 21-0 25-8 Note b
9-10 14-4 18-2 22-3 25-9
Spruce-pine-fir                        #3
8-7 12-6 15-10 19-5 22-6 7-5 10-10 13-9 16-9 19-6
16 Douglas fir-larch                     SS
10-5 16-4 21-7 Note b Note b 10-5 16-3 20-7 25-2 Note b
Douglas fir-larch                     #1
10-0 15-4 19-5 23-9 Note b 9-1 13-3 16-10 20-7 23-10
Douglas fir-larch                     #2 9-10 14-7 18-5 22-6 26-0 8-7 12-7 16-0 19-6 22-7
Douglas fir-larch                     #3 7-7 11-1 14-1 17-2 19-11 6-7 9-8 12-12 14-11 17-3
Hem-fir                                    SS
9-10 15-6 20-5 Note b Note b 9-10 15-6 19-11 24-4 Note b
Hem-fir                                    #1 9-8 15-2 19-2 23-5 Note b 9-0 13-1 16-7 20-4 23-7
Hem-fir                                    #2 9-2 14-2 17-11 21-11 25-5 8-5 12-3 15-6 18-11 22-0
Hem-fir                                    #3 7-5 10-10 13-9 16-9 19-6 6-5 9-5 11-11 14-6 16-10
Southern pine                         SS
10-3 16-1 21-2 Note b Note b 10-3 16-1 21-2 25-7 Note b
Southern pine                         #1 9-10 15-6 19-10 23-2 Note b 9-1 13-7 17-2 20-1 23-10
Southern pine                         #2 9-0 13-6 17-1 20-3 23-10 7-9 11-8 14-9 17-6 20-8
Southern pine                         #3 6-11 10-2 12-10 15-7 18-6 6-0 8-10 11-2 13-6 16-0
Spruce-pine-fir                        SS
9-8 15-2 19-11 25-5 Note b 9-8 14-10 18-10 23-0 Note b
Spruce-pine-fir                        #1 9-5 14-4 18-2 22-3 25-9 8-6 12-5 15-9 19-3 22-4
Spruce-pine-fir                        #2 9-5 14-4 18-2 22-3 25-9 8-6 12-5 15-9 19-3 22-4
Spruce-pine-fir                        #3 7-5 10-10 13-9 16-9 19-6 6-5 9-5 11-11 14-6 16-10
19.2 Douglas fir-larch                     SS
9-10 15-5 20-4 25-11 Note b 9-10 14-10 18-10 23-0 Note b
Douglas fir-larch                     #1 9-5 14-0 17-9 21-8 25-2 8-4 12-2 15-4 18-9 21-9
Douglas fir-larch                     #2 9-1 13-3 16-10 20-7 23-10 7-10 11-6 14-7 17-10 20-8
Douglas fir-larch                     #3 6-11 10-2 12-10 15-8 18-3 6-0 8-9 11-2 12-7 15-9
Hem-fir                                    SS
9-3 14-7 19-2 24-6 Note b 9-3 14-4 18-2 22-3 25-9
Hem-fir                                    #1 9-1 13-10 17-6 21-5 24-10 8-2 12-0 15-2 18-6 21-6
Hem-fir                                    #2 8-8 12-11 16-4 20-0 23-2 7-8 11-2 14-2 17-4 20-1
Hem-fir                                    #3 6-9 9-11 12-7 15-4 17-9 5-10 8-7 10-10 13-3 15-5
Southern pine                         SS
9-8 15-2 19-11 25-5 Note b 9-8 15-2 19-7 23-4 Note b
Southern pine                         #1 9-3 14-3 18-1 21-2 25-2 8-4 12-4 15-8 18-4 21-9
Southern pine                         #2 8-2 12-3 15-7 18-6 21-9 7-1 10-8 13-6 16-0 18-10
Southern pine                         #3 6-4 9-4 11-9 14-3 16-10 5-6 8-1 10-2 12-4 14-7
Spruce-pine-fir                        SS
9-1 14-3 18-9 23-11 Note b 9-1 13-7 17-2 21-0 24-4
Spruce-pine-fir                        #1 8-10 13-1 16-7 20-3 23-6 7-9 11-4 14-4 17-7 20-4
Spruce-pine-fir                        #2 8-10 13-1 16-7 20-3 23-6 7-9 11-4 14-4 17-7 20-4
Spruce-pine-fir                        #3 6-9 9-11 12-7 15-4 17-9 5-10 8-7 10-10 13-3 15-5
24 Douglas fir-larch                     SS
9-1 14-4 18-10 23-9 Note b 9-1 13-3 16-10 20-7 23-10
Douglas fir-larch                     #1 8-7 12-6 15-10 19-5 22-6 7-5 10-10 13-9 16-9 19-6
Douglas fir-larch                     #2 8-2 11-11 15-1 18-5 21-4 7-0 10-4 13-0 15-11 18-6
Douglas fir-larch                     #3 6-2 9-1 11-6 14-1 16-3 5-4 7-10 10-0 12-2 14-1
Hem-fir                                    SS
8-7 13-6 17-10 22-9 Note b 8-7 12-10 16-3 19-10 23-0
Hem-fir                                    #1 8-5 12-4 15-8 19-2 22-2 7-4 10-9 13-7 16-7 19-3
Hem-fir                                    #2 7-11 11-7 14-8 17-10 20-9 6-10 10-0 12-8 15-6 17-11
Hem-fir                                    #3 6-1 8-10 11-3 13-8 15-11 5-3 7-8 9-9 11-10 13-9
Southern pine                         SS
8-11 14-1 18-6 23-8 Note b 8-11 13-10 17-6 20-10 24-8
Southern pine                         #1 8-7 12-9 16-2 18-11 22-6 7-5 11-1 14-0 16-5 19-6
Southern pine                         #2 7-4 11-0 10-11 16-6 19-6 6-4 9-6 12-1 14-4 16-10
Southern pine                         #3 5-8 8-4 10-6 12-9 15-1 4-11 7-3 9-1 11-0 13-1
Spruce-pine-fir                        SS
8-5 13-3 17-5 21-8 25-2 8-4 12-2 15-4 18-9 21-9
Spruce-pine-fir                        #1 8-0 11-9 14-10 18-2 21-0 6-11 10-2 12-10 15-8 18-3
Spruce-pine-fir                        #2 8-0 11-9 14-10 18-2 21-0 6-11 10-2 12-10 15-8 18-3
Spruce-pine-fir                        #3 6-1 8-10 11-3 13-8 15-11 5-3 7-8 9-9 11-10 13-9
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
  1. Span exceeds 26 feet in length.



TABLE R802.5.1(2)
RAFTER SPANS FOR COMMON LUMBER SPECIES
(Roof live load = 20 psf, ceiling attached to rafters, L/Δ = 240)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
10-5 16-4 21-7 Note b Note b 10-5 16-4 21-7 Note b Note b
Douglas fir-larch                     #1
10-0 15-9 20-10 Note b Note b 10-0 15-4 19-5 23-9 Note b
Douglas fir-larch                     #2
9-10 15-6 20-5 26-0 Note b 9-10 14-7 18-5 22-6 26-0
Douglas fir-larch                     #3
8-9 12-10 16-3 19-10 23-0 7-7 11-1 14-1 17-2 9-11
Hem-fir                                    SS
9-10 15-6 20-5 Note b Note b 9-10 15-6 20-5 Note b Note b
Hem-fir                                    #1
9-8 15-2 19-11 25-5 Note b 9-8 15-2 19-2 23-5 Note b
Hem-fir                                    #2
9-2 14-5 19-0 24-3 Note b 9-2 14-2 17-11 21-11 25-5
Hem-fir                                    #3
8-7 12-6 15-10 19-5 22-6 7-5 10-10 13-9 16-9 19-6
Southern pine                         SS
10-3 16-1 21-2 Note b Note b 10-3 16-1 21-2 Note b Note b
Southern pine                         #1
9-10 15-6 20-5 Note b Note b 9-10 15-6 19-10 23-2 Note b
Southern pine                         #2
9-5 14-9 19-6 23-5 Note b 9-0 13-6 17-1 20-3 23-10
Southern pine                         #3
8-0 11-9 14-10 18-0 21-4 6-11 10-2 12-10 15-7 18-6
Spruce-pine-fir                        SS
9-8 15-2 19-11 25-5 Note b 9-8 15-2 19-11 25-5 Note b
Spruce-pine-fir                        #1
9-5 14-9 19-6 24-10 Note b 9-5 14-4 18-2 22-3 25-9
Spruce-pine-fir                        #2
9-5 14-9 19-6 24-10 Note b 9-5 14-4 18-2 22-3 25-9
Spruce-pine-fir                        #3
8-7 12-6 15-10 19-5 22-6 7-5 10-10 13-9 16-9 19-6
16 Douglas fir-larch                     SS
9-6 14-11 19-7 25-0 Note b 9-6 14-11 19-7 25-0 Note b
Douglas fir-larch                     #1
9-1 14-4 18-11 23-9 Note b 9-1 13-3 16-10 20-7 23-10
Douglas fir-larch                     #2 8-11 14-1 18-5 22-6 26-0 8-7 12-7 16-0 19-6 22-7
Douglas fir-larch                     #3 7-7 11-1 14-1 17-2 19-11 6-7 9-8 12-2 14-11 17-3
Hem-fir                                    SS
8-11 14-1 18-6 23-8 Note b 8-11 14-1 18-6 23-8 Note b
Hem-fir                                    #1 8-9 13-9 18-1 23-1 Note b 8-9 13-1 16-7 20-4 23-7
Hem-fir                                    #2 8-4 13-1 17-3 21-11 25-5 8-4 12-3 15-6 18-11 22-0
Hem-fir                                    #3 7-5 10-10 13-9 16-9 19-6 6-5 9-5 11-11 14-6 16-10
Southern pine                         SS
9-4 14-7 19-3 24-7 Note b 9-4 14-7 19-3 24-7 Note b
Southern pine                         #1 8-11 14-1 18-6 23-2 Note b 8-11 13-7 17-2 20-1 23-10
Southern pine                         #2 8-7 13-5 17-1 20-3 23-10 7-9 11-8 14-9 17-6 20-8
Southern pine                         #3 6-11 10-2 12-10 15-7 18-6 6-0 8-10 11-2 13-6 16-0
Spruce-pine-fir                        SS
8-9 13-9 18-1 23-1 Note b 8-9 13-9 18-1 23-0 Note b
Spruce-pine-fir                        #1 8-7 13-5 17-9 22-3 25-9 8-6 12-5 15-9 19-3 22-4
Spruce-pine-fir                        #2 8-7 13-5 17-9 22-3 25-9 8-6 12-5 15-9 19-3 22-4
Spruce-pine-fir                        #3 7-5 10-10 13-9 16-9 19-6 6-5 9-5 11-11 14-6 16-10
19.2 Douglas fir-larch                     SS
8-11 14-0 18-5 23-7 Note b 8-11 14-0 18-5 23-0 Note b
Douglas fir-larch                     #1 8-7 13-6 17-9 21-8 25-2 8-4 12-2 15-4 18-9 21-9
Douglas fir-larch                     #2 8-5 13-3 16-10 20-7 23-10 7-10 11-6 14-7 17-10 20-8
Douglas fir-larch                     #3 6-11 10-2 12-10 15-8 18-3 6-0 8-9 11-2 13-7 15-9
Hem-fir                                    SS
8-5 13-3 17-5 22-3 Note b 8-5 13-3 17-5 22-3 25-9
Hem-fir                                    #1 8-3 12-11 17-1 21-5 24-10 8-2 12-0 15-2 18-6 21-6
Hem-fir                                    #2 7-10 12-4 16-3 20-0 23-2 7-8 11-2 14-2 17-4 20-1
Hem-fir                                    #3 6-9 9-11 12-7 15-4 17-9 5-10 8-7 10-10 13-3 15-5
Southern pine                         SS
8-9 13-9 18-2 23-1 Note b 8-9 13-9 18-2 23-1 Note b
Southern pine                         #1 8-5 13-3 17-5 21-2 25-2 8-4 12-4 15-8 18-4 21-9
Southern pine                         #2 8-1 12-3 15-7 18-6 21-9 7-1 10-8 13-6 16-0 18-10
Southern pine                         #3 6-4 9-4 11-9 14-3 16-10 5-6 8-1 10-2 12-4 14-7
Spruce-pine-fir                        SS
8-3 12-11 17-1 21-9 Note b 8-3 12-11 17-1 21-0 24-4
Spruce-pine-fir                        #1 8-1 12-8 16-7 20-3 23-6 7-9 11-4 14-4 17-7 20-4
Spruce-pine-fir                        #2 8-1 12-8 16-7 20-3 23-6 7-9 11-4 14-4 17-7 20-4
Spruce-pine-fir                        #3 6-9 9-11 12-7 15-4 17-9 5-10 8-7 10-10 13-3 15-5
24 Douglas fir-larch                     SS
8-3 13-0 17-2 21-10 Note b 8-3 13-0 16-10 20-7 23-10
Douglas fir-larch                     #1 8-0 12-6 15-10 19-5 22-6 7-5 10-10 13-9 16-9 19-6
Douglas fir-larch                     #2 7-10 11-11 15-1 18-5 21-4 7-0 10-4 13-0 15-11 18-6
Douglas fir-larch                     #3 6-2 9-1 11-6 14-1 16-3 5-4 7-10 10-0 12-2 14-1
Hem-fir                                    SS
7-10 12-3 16-2 20-8 25-1 7-10 12-3 16-2 19-10 23-0
Hem-fir                                    #1 7-8 12-0 15-8 19-2 22-2 7-4 10-9 13-7 16-7 19-3
Hem-fir                                    #2 7-3 11-5 14-8 17-10 20-9 6-10 10-0 12-8 15-6 17-11
Hem-fir                                    #3 6-1 8-10 11-3 13-8 15-11 5-3 7-8 9-9 11-10 13-9
Southern pine                         SS
8-1 12-9 16-10 21-6 Note b 8-1 12-9 16-10 20-10 24-8
Southern pine                         #1 7-10 12-3 16-2 18-11 22-6 7-5 11-1 14-0 16-5 19-6
Southern pine                         #2 7-4 11-0 13-11 16-6 19-6 6-4 9-6 12-1 14-4 16-10
Southern pine                         #3 5-8 8-4 10-6 12-9 15-1 4-11 7-3 9-1 11-0 13-1
Spruce-pine-fir                        SS
7-8 12-0 15-10 20-2 24-7 7-8 12-0 15-4 18-9 21-9
Spruce-pine-fir                        #1 7-6 11-9 14-10 18-2 21-0 6-11 10-2 12-10 15-8 18-3
Spruce-pine-fir                        #2 7-6 11-9 14-10 18-2 21-0 6-11 10-2 12-10 15-8 18-3
Spruce-pine-fir                        #3 6-1 8-10 11-3 13-8 15-11 5-3 7-8 9-9 11-10 13-9
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
  1. Span exceeds 26 feet in length.



TABLE R802.5.1(3)
RAFTER SPANS FOR COMMON LUMBER SPECIES
(Ground snow load = 30 psf, ceiling not attached to rafters, L/Δ = 180)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
10-0 15-9 20-9 Note b Note b 10-0 15-9 20-5 24-11 Note b
Douglas fir-larch                     #1
9-8 14-9 18-8 22-9 Note b 9-0 13-2 16-8 20-4 23-7
Douglas fir-larch                     #2
9-6 14-0 17-8 21-7 25-1 8-6 12-6 15-10 19-4 22-5
Douglas fir-larch                     #3
7-3 10-8 13-6 16-6 19-2 6-6 9-6 12-1 14-9 17-1
Hem-fir                                    SS
9-6 14-10 19-7 25-0 Note b 9-6 14-10 19-7 24-1 Note b
Hem-fir                                    #1
9-3 14-6 18-5 22-6 26-0 8-11 13-0 16-6 20-1 23-4
Hem-fir                                    #2
8-10 13-7 17-2 21-0 24-4 8-4 12-2 15-4 18-9 21-9
Hem-fir                                    #3
7-1 10-5 13-2 16-1 18-8 6-4 9-4 11-9 14-5 16-8
Southern pine                          SS
9-10 15-6 20-5 Note b Note b 9-10 15-6 20-5 25-4 Note b
Southern pine                          #1
9-6 14-10 19-0 22-3 Note b 9-0 13-5 17-0 19-11 23-7
Southern pine                          #2
8-7 12-11 16-4 19-5 22-10 7-8 11-7 14-8 17-4 20-5
Southern pine                          #3
6-7 9-9 12-4 15-0 17-9 5-11 8-9 11-0 13-5 15-10
Spruce-pine-fir                        SS
9-3 14-7 19-2 24-6 Note b 9-3 14-7 18-8 22-9 Note b
Spruce-pine-fir                        #1
9-1 13-9 17-5 21-4 24-8 8-5 12-4 15-7 19-1 22-1
Spruce-pine-fir                        #2
9-1 13-9 17-5 21-4 24-8 8-5 12-4 15-7 19-1 22-1
Spruce-pine-fir                        #3
7-1 10-5 13-2 16-1 18-8 6-4 9-4 11-9 14-5 16-8
16 Douglas fir-larch                     SS
9-1 14-4 18-10 24-1 Note b 9-1 14-0 17-8 21-7 25-1
Douglas fir-larch                     #1
8-9 12-9 16-2 19-9 22-10 7-10 11-5 14-5 17-8 20-5
Douglas fir-larch                     #2 8-3 12-1 15-4 18-9 21-8 7-5 10-10 13-8 16-9 19-5
Douglas fir-larch                     #3 6-4 9-3 11-8 14-3 16-7 5-8 8-3 10-6 12-9 14-10
Hem-fir                                    SS
8-7 13-6 17-10 22-9 Note b 8-7 13-6 17-1 20-10 24-2
Hem-fir                                    #1 8-5 12-7 15-11 19-6 22-7 7-8 11-3 14-3 17-5 20-2
Hem-fir                                    #2 8-0 11-9 14-11 18-2 21-1 7-2 10-6 13-4 16-3 18-10
Hem-fir                                    #3 6-2 9-0 11-5 13-11 16-2 5-6 8-1 10-3 12-6 14-6
Southern pine                          SS
8-11 14-1 18-6 23-8 Note b 8-11 14-1 18-5 1-11 25-11
Southern pine                          #1 8-7 13-0 16-6 19-3 22-10 7-10 11-7 14-9 17-3 20-5
Southern pine                          #2 7-6 11-2 14-2 16-10 19-10 6-8 10-0 12-8 15-1 17-9
Southern pine                          #3 5-9 8-6 10-8 13-0 15-4 5-2 7-7 9-7 11-7 13-9
Spruce-pine-fir                        SS
8-5 13-3 17-5 22-1 25-7 8-5 12-9 16-2 19-9 22-10
Spruce-pine-fir                        #1 8-2 11-11 15-1 18-5 21-5 7-3 10-8 13-6 16-6 19-2
Spruce-pine-fir                        #2 8-2 11-11 15-1 18-5 21-5 7-3 10-8 13-6 16-6 19-2
Spruce-pine-fir                        #3 6-2 9-0 11-5 13-11 16-2 5-6 8-1 10-3 12-6 14-6
19.2 Douglas fir-larch                     SS
8-7 13-6 17-9 22-1 25-7 8-7 12-9 16-2 19-9 22-10
Douglas fir-larch                     #1 7-11 11-8 14-9 18-0 20-11 7-1 10-5 13-2 16-1 18-8
Douglas fir-larch                     #2 7-7 11-0 14-0 17-1 19-10 6-9 9-10 12-6 15-3 17-9
Douglas fir-larch                     #3 5-9 8-5 10-8 13-1 15-2 5-2 7-7 9-7 11-8 13-6
Hem-fir                                    SS
8-1 12-9 16-9 21-4 24-8 8-1 12-4 15-7 19-1 22-1
Hem-fir                                    #1 7-10 11-6 14-7 17-9 20-7 7-0 10-3 13-0 15-11 18-5
Hem-fir                                    #2 7-4 10-9 13-7 16-7 19-3 6-7 9-7 12-2 14-10 17-3
Hem-fir                                    #3 5-7 8-3 10-5 12-9 14-9 5-0 7-4 9-4 11-5 13-2
Southern pine                          SS
8-5 13-3 17-5 22-3 Note b 8-5 13-3 16-10 20-0 23-7
Southern pine                          #1 8-0 11-10 15-1 17-7 20-11 7-1 10-7 13-5 15-9 18-8
Southern pine                          #2 6-10 10-2 12-11 15-4 18-1 6-1 9-2 11-7 13-9 16-2
Southern pine                          #3 5-3 7-9 9-9 11-10 14-0 4-8 6-11 8-9 10-7 12-6
Spruce-pine-fir                        SS
7-11 12-5 16-5 20-2 23-4 7-11 11-8 14-9 18-0 20-11
Spruce-pine-fir                        #1 7-5 10-11 13-9 16-10 19-6 6-8 9-9 12-4 15-1 17-6
Spruce-pine-fir                        #2 7-5 10-11 13-9 16-10 19-6 6-8 9-9 12-4 15-1 17-6
Spruce-pine-fir                        #3 5-7 8-3 10-5 12-9 14-9 5-0 7-4 9-4 11-5 13-2
24 Douglas fir-larch                     SS
8-0 12-6 16-2 19-9 22-10 7-10 11-5 14-5 17-8 20-5
Douglas fir-larch                     #1 7-1 10-5 13-2 16-1 18-8 6-4 9-4 11-9 14-5 16-8
Douglas fir-larch                     #2 6-9 9-10 12-6 15-3 17-9 6-0 8-10 11-2 13-8 15-10
Douglas fir-larch                     #3 5-2 7-7 9-7 11-8 13-6 4-7 6-9 8-7 10-5 12-1
Hem-fir                                    SS
7-6 11-10 15-7 19-1 22-1 7-6 11-0 13-11 17-0 19-9
Hem-fir                                    #1 7-0 10-3 13-0 15-11 18-5 6-3 9-2 11-8 14-3 16-6
Hem-fir                                    #2 6-7 9-7 12-2 14-10 17-3 5-10 8-7 10-10 13-3 15-5
Hem-fir                                    #3 5-0 7-4 9-4 11-5 13-2 4-6 6-7 8-4 10-2 11-10
Southern pine                          SS
7-10 12-3 16-2 20-0 23-7 7-10 11-10 15-0 17-11 21-2
Southern pine                          #1 7-1 10-7 13-5 15-9 18-8 6-4 9-6 12-0 14-1 16-8
Southern pine                          #2 6-1 9-2 11-7 13-9 16-2 5-5 8-2 10-4 12-3 14-6
Southern pine                          #3 4-8 6-11 8-9 10-7 12-6 4-2 6-2 7-10 9-6 11-2
Spruce-pine-fir                        SS
7-4 11-7 14-9 18-0 20-11 7-1 10-5 13-2 16-1 18-8
Spruce-pine-fir                        #1 6-8 9-9 12-4 15-1 17-6 5-11 8-8 11-0 13-6 15-7
Spruce-pine-fir                        #2 6-8 9-9 12-4 15-1 17-6 5-11 8-8 11-0 13-6 15-7
Spruce-pine-fir                        #3 5-0 7-4 9-4 11-5 13-2 4-6 6-7 8-4 10-2 11-10
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
  1. Span exceeds 26 feet in length.



TABLE R802.5.1(4)
RAFTER SPANS FOR COMMON LUMBER SPECIES
(Ground snow load = 50 psf, ceiling not attached to rafters, L/Δ = 180)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
8-5 13-3 17-6 22-4 26-0 8-5 13-3 17-3 21-1 24-5
Douglas fir-larch                     #1
8-2 12-0 15-3 18-7 21-7 7-7 11-2 14-1 17-3 20-0
Douglas fir-larch                     #2
7-10 11-5 14-5 17-8 20-5 7-3 10-7 13-4 16-4 18-11
Douglas fir-larch                     #3
6-0 8-9 11-0 13-6 15-7 5-6 8-1 10-3 12-6 14-6
Hem-fir                                    SS
8-0 12-6 16-6 21-1 25-6 8-0 12-6 16-6 20-4 23-7
Hem-fir                                    #1
7-10 11-10 15-0 18-4 21-3 7-6 11-0 13-11 17-0 19-9
Hem-fir                                    #2
7-5 11-1 14-0 17-2 19-11 7-0 10-3 13-0 15-10 18-5
Hem-fir                                    #3
5-10 8-6 10-9 13-2 15-3 5-5 7-10 10-0 12-2 14-1
Southern pine                         SS
8-4 13-1 17-2 21-11 Note b 8-4 13-1 17-2 21-5 25-3
Southern pine                         #1
8-0 12-3 15-6 18-2 21-7 7-7 11-4 14-5 16-10 20-0
Southern pine                         #2
7-0 10-6 13-4 15-10 18-8 6-6 9-9 12-4 14-8 17-3
Southern pine                         #3
5-5 8-0 10-1 12-3 14-6 5-0 7-5 9-4 11-4 13-5
Spruce-pine-fir                        SS
7-10 12-3 16-2 20-8 24-1 7-10 12-3 15-9 19-3 22-4
Spruce-pine-fir                        #1
7-8 11-3 14-3 17-5 20-2 7-1 10-5 13-2 16-1 18-8
Spruce-pine-fir                        #2
7-8 11-3 14-3 17-5 20-2 7-1 10-5 13-2 16-1 18-8
Spruce-pine-fir                        #3
5-10 8-6 10-9 13-2 15-3 5-5 7-10 10-0 12-2 14-1
16 Douglas fir-larch                     SS
7-8 12-1 15-11 19-9 22-10 7-8 11-10 14-11 18-3 21-2
Douglas fir-larch                     #1
7-1 10-5 13-2 16-1 18-8 6-7 9-8 12-2 14-11 17-3
Douglas fir-larch                     #2 6-9 9-10 12-6 15-3 17-9 6-3 9-2 11-7 14-2 16-5
Douglas fir-larch                     #3 5-2 7-7 9-7 11-18 13-6 4-9 7-0 8-10 10-10 12-6
Hem-fir                                    SS
7-3 11-5 15-0 19-1 22-1 7-3 11-5 14-5 17-8 20-5
Hem-fir                                    #1 7-0 10-3 13-0 15-11 18-5 6-6 9-6 12-1 14-9 17-1
Hem-fir                                    #2 6-7 9-7 12-2 14-10 17-3 6-1 8-11 11-3 13-9 15-11
Hem-fir                                    #3 5-0 7-4 9-4 11-5 13-2 4-8 6-10 8-8 10-6 12-3
Southern pine                         SS
7-6 11-10 15-7 19-11 23-7 7-6 11-10 15-7 18-6 21-10
Southern pine                         #1 7-1 10-7 13-5 15-9 18-8 6-7 9-10 12-5 14-7 17-3
Southern pine                         #2 6-1 9-2 11-7 13-9 16-2 5-8 8-5 10-9 12-9 15-0
Southern pine                         #3 4-8 6-11 8-9 10-7 12-6 4-4 6-5 8-1 9-10 11-7
Spruce-pine-fir                        SS
7-1 11-2 14-8 18-0 20-11 7-1 10-9 13-8 15-11 19-4
Spruce-pine-fir                        #1 6-8 9-9 12-4 15-1 17-6 6-2 9-0 11-5 13-11 16-2
Spruce-pine-fir                        #2 6-8 9-9 12-4 15-1 17-6 6-2 9-0 11-5 13-11 16-2
Spruce-pine-fir                        #3 5-0 7-4 9-4 11-5 13-2 4-8 6-10 8-8 10-6 12-3
19.2 Douglas fir-larch                     SS
7-3 11-4 14-9 18-0 20-11 7-3 10-9 13-8 16-8 19-4
Douglas fir-larch                     #1 6-6 9-6 12-0 14-8 17-1 6-0 8-10 11-2 13-7 15-9
Douglas fir-larch                     #2 6-2 9-0 11-5 13-11 16-2 5-8 8-4 10-9 12-11 15-0
Douglas fir-larch                     #3 4-8 6-11 8-9 10-8 12-4 4-4 6-4 8-1 9-10 11-5
Hem-fir                                    SS
6-10 10-9 14-2 17-5 20-2 6-10 10-5 13-2 16-1 18-8
Hem-fir                                    #1 6-5 9-5 11-11 14-6 16-10 8-11 8-8 11-0 13-5 15-7
Hem-fir                                    #2 6-0 8-9 11-1 13-7 15-9 5-7 8-1 10-3 12-7 14-7
Hem-fir                                    #3 4-7 6-9 8-6 10-5 12-1 4-3 6-3 7-11 9-7 11-2
Southern pine                         SS
7-1 11-2 14-8 18-3 21-7 7-1 11-2 14-2 16-11 20-0
Southern pine                         #1 6-6 9-8 12-3 14-4 17-1 6-0 9-0 11-4 13-4 15-9
Southern pine                         #2 5-7 8-4 10-7 12-6 14-9 5-2 7-9 9-9 11-7 13-8
Southern pine                         #3 4-3 6-4 8-0 9-8 11-5 4-0 5-10 7-4 8-11 10-7
Spruce-pine-fir                        SS
6-8 10-6 13-5 16-5 19-1 6-8 9-10 12-5 15-3 17-8
Spruce-pine-fir                        #1 6-1 8-11 11-3 13-9 15-11 5-7 8-3 10-5 12-9 14-9
Spruce-pine-fir                        #2 6-1 8-11 11-3 13-9 15-11 5-7 8-3 10-5 12-9 14-9
Spruce-pine-fir                        #3 4-7 6-9 8-6 10-5 12-1 4-3 6-3 7-11 9-7 11-2
24 Douglas fir-larch                     SS
6-8 10-5 13-2 16-1 18-8 6-7 9-8 12-2 14-11 17-3
Douglas fir-larch                     #1 5-10 8-6 10-9 13-2 15-3 5-5 7-10 10-0 12-2 14-1
Douglas fir-larch                     #2 5-6 8-1 10-3 12-6 14-6 5-1 7-6 9-5 11-7 13-5
Douglas fir-larch                     #3 4-3 6-2 7-10 9-6 11-1 3-11 5-8 7-3 8-10 10-3
Hem-fir                                    SS
6-4 9-11 12-9 15-7 18-0 6-4 9-4 11-9 14-5 16-8
Hem-fir                                    #1 5-9 8-5 10-8 13-0 15-1 8-4 7-9 9-10 12-0 13-11
Hem-fir                                    #2 5-4 7-10 9-11 12-1 14-1 4-11 7-3 9-2 11-3 13-0
Hem-fir                                    #3 4-1 6-0 7-7 9-4 10-9 3-10 5-7 7-1 8-7 10-0
Southern pine                         SS
6-7 10-4 13-8 16-4 19-3 6-7 10-0 12-8 15-2 17-10
Southern pine                         #1 5-10 8-8 11-0 12-10 15-3 5-5 8-0 10-2 11-11 14-1
Southern pine                         #2 5-0 7-5 9-5 11-3 13-2 4-7 6-11 8-9 10-5 12-3
Southern pine                         #3 3-10 5-8 7-1 8-8 10-3 3-6 5-3 6-7 8-0 9-6
Spruce-pine-fir                        SS
6-2 9-6 12-0 14-8 17-1 6-0 8-10 11-2 13-7 15-9
Spruce-pine-fir                        #1 5-5 7-11 10-1 12-4 14-3 5-0 7-4 9-4 11-5 13-2
Spruce-pine-fir                        #2 5-5 7-11 10-1 12-4 14-3 5-0 7-4 9-4 11-5 13-2
Spruce-pine-fir                        #3 4-1 6-0 7-7 9-4 10-9 3-10 5-7 7-1 8-7 10-0
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
  1. Span exceeds 26 feet in length.



TABLE R802.5.1(5)
RAFTER SPANS FOR COMMON LUMBER SPECIES
(Ground snow load= 30 psf, ceiling attached to rafters, L/Δ = 240)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
9-1 14-4 18-10 24-1 Note b 9-1 14-4 18-10 24-1 Note b
Douglas fir-larch                     #1
8-9 13-9 18-2 22-9 Note b 8-9 13-2 16-8 20-4 23-7
Douglas fir-larch                     #2
8-7 13-6 17-8 21-7 25-1 8-6 12-6 15-10 19-4 22-5
Douglas fir-larch                     #3
7-3 10-8 13-6 16-6 19-2 6-6 9-6 12-1 14-9 17-1
Hem-fir                                    SS
8-7 13-6 17-10 22-9 Note b 8-7 13-6 17-10 22-9 Note b
Hem-fir                                    #1
8-5 13-3 17-5 22-3 26-0 8-5 13-0 16-6 20-1 23-4
Hem-fir                                    #2
8-0 12-7 16-7 21-0 24-4 8-0 12-2 15-4 18-9 21-9
Hem-fir                                    #3
7-1 10-5 13-2 16-1 18-8 6-4 9-4 11-9 14-5 16-8
Southern pine                         SS
8-11 14-1 18-6 23-8 Note b 8-11 14-1 18-6 23-8 Note b
Southern pine                         #1
8-7 13-6 17-10 22-3 Note b 8-7 13-5 17-0 19-11 23-7
Southern pine                         #2
8-3 12-11 16-4 19-5 22-10 7-8 11-7 14-8 17-4 20-5
Southern pine                         #3
6-7 9-9 12-4 15-0 17-9 5-1 18-9 11-0 13-5 15-10
Spruce-pine-fir                        SS
8-5 13-3 17-5 22-3 Note b 8-5 13-3 17-5 22-3 Note b
Spruce-pine-fir                        #1
8-3 12-11 17-0 21-4 24-8 8-3 12-4 15-7 19-1 22-1
Spruce-pine-fir                        #2
8-3 12-11 17-0 21-4 24-8 8-3 12-4 15-7 19-1 22-1
Spruce-pine-fir                        #3
7-1 10-5 13-2 16-1 18-8 6-4 9-4 11-9 14-5 16-8
16 Douglas fir-larch                     SS
8-3 13-0 17-2 21-10 Note b 8-3 13-0 17-2 21-7 25-1
Douglas fir-larch                     #1
8-0 12-6 16-2 19-9 22-10 7-10 11-5 14-5 17-8 20-5
Douglas fir-larch                     #2 7-10 12-1 15-4 18-9 21-8 7-5 10-10 13-8 16-9 19-5
Douglas fir-larch                     #3 6-4 9-3 11-8 14-3 16-7 5-8 8-3 10-6 12-9 14-10
Hem-fir                                    SS
7-10 12-3 16-2 20-8 25-1 7-10 12-3 16-2 20-8 24-2
Hem-fir                                    #1 7-8 12-0 15-10 19-6 22-7 7-8 11-3 14-3 17-5 20-2
Hem-fir                                    #2 7-3 11-5 14-11 18-2 21-1 7-2 10-6 13-4 16-3 18-10
Hem-fir                                    #3 6-2 9-0 11-5 13-11 16-2 5-6 8-1 10-3 12-6 14-6
Southern pine                         SS
8-1 12-9 16-10 21-6 Note b 8-1 12-9 16-10 21-6 25-11
Southern pine                         #1 7-10 12-3 16-2 19-3 22-10 7-10 11-7 14-9 17-3 20-5
Southern pine                         #2 7-6 11-2 14-2 16-10 19-10 6-8 10-0 12-8 15-1 17-9
Southern pine                         #3 5-9 8-6 10-8 13-0 15-4 5-2 7-7 9-7 11-7 13-9
Spruce-pine-fir                        SS
7-8 12-0 15-10 20-2 24-7 7-8 12-0 15-10 19-9 22-10
Spruce-pine-fir                        #1 7-6 11-9 15-1 18-5 21-5 7-3 10-8 13-6 16-6 19-2
Spruce-pine-fir                        #2 7-6 11-9 15-1 18-5 21-5 7-3 10-8 13-6 16-6 19-2
Spruce-pine-fir                        #3 6-2 9-0 11-5 13-11 16-2 5-6 8-1 10-3 12-6 14-6
19.2 Douglas fir-larch                     SS
7-9 12-3 16-1 20-7 25-0 7-9 12-3 16-1 19-9 22-10
Douglas fir-larch                     #1 7-6 11-8 14-9 18-0 20-11 7-1 10-5 13-2 16-1 18-8
Douglas fir-larch                     #2 7-4 11-0 14-0 17-1 19-10 6-9 9-1 12-6 15-3 17-9
Douglas fir-larch                     #3 5-9 8-5 10-8 13-1 15-2 5-2 7-7 9-7 11-8 13-6
Hem-fir                                    SS
7-4 11-7 15-3 19-5 23-7 7-4 11-7 15-3 19-1 22-1
Hem-fir                                    #1 7-2 11-4 14-7 17-9 20-7 7-0 16-3 13-0 15-11 18-5
Hem-fir                                    #2 6-10 10-9 13-7 16-7 19-3 6-7 9-7 12-2 14-10 17-3
Hem-fir                                    #3 5-7 8-3 10-5 12-9 14-9 5-0 7-4 9-4 11-5 13-2
Southern pine                         SS
7-8 12-0 15-10 20-2 24-7 7-8 12-0 15-10 20-0 23-7
Southern pine                         #1 7-4 11-7 15-1 17-7 20-11 7-1 10-7 13-5 15-9 18-8
Southern pine                         #2 6-10 10-2 12-11 15-4 18-1 6-1 9-2 11-7 13-9 16-2
Southern pine                         #3 5-3 7-9 9-9 11-10 14-0 4-8 6-11 8-9 10-7 12-6
Spruce-pine-fir                        SS
7-2 11-4 14-11 19-0 23-1 7-2 11-4 14-9 18-0 20-11
Spruce-pine-fir                        #1 7-0 10-11 13-9 16-10 19-6 6-8 9-9 12-4 15-1 17-6
Spruce-pine-fir                        #2 7-0 10-11 13-9 16-10 19-6 6-8 9-9 12-4 15-1 17-6
Spruce-pine-fir                        #3 5-7 8-3 10-5 12-9 14-9 5-0 7-4 9-4 11-5 13-2
24 Douglas fir-larch                     SS
7-3 11-4 15-0 19-1 22-10 7-3 11-4 14-5 17-8 20-5
Douglas fir-larch                     #1 7-0 10-5 13-2 16-1 18-8 6-4 9-4 11-9 14-5 16-8
Douglas fir-larch                     #2 6-9 9-10 12-6 15-3 17-9 6-0 8-10 11-2 13-8 15-10
Douglas fir-larch                     #3 5-2 7-7 9-7 11-8 13-6 4-7 6-9 8-7 10-5 12-1
Hem-fir                                    SS
6-10 10-9 14-2 18-0 21-11 6-10 10-9 13-11 17-0 19-9
Hem-fir                                    #1 6-8 10-3 13-0 15-11 18-5 6-3 9-2 11-8 14-3 16-6
Hem-fir                                    #2 6-4 9-7 12-2 14-10 17-3 5-10 8-7 10-10 13-3 15-5
Hem-fir                                    #3 5-0 7-4 9-4 11-5 13-2 4-6 6-7 8-4 10-2 11-10
Southern pine                         SS
7-1 11-2 14-8 18-9 22-10 7-1 11-2 14-8 17-11 21-2
Southern pine                         #1 6-10 10-7 13-5 15-9 18-8 6-4 9-6 12-0 14-1 16-8
Southern pine                         #2 6-1 9-2 11-7 13-9 16-2 5-5 8-2 10-4 12-3 14-6
Southern pine                         #3 4-8 6-11 8-9 10-7 12-6 4-2 6-2 7-10 9-6 11-2
Spruce-pine-fir                        SS
6-8 10-6 13-10 17-8 20-11 6-8 10-5 13-2 16-1 18-8
Spruce-pine-fir                        #1 6-6 9-9 12-4 15-1 17-6 5-11 8-8 11-0 13-6 15-7
Spruce-pine-fir                        #2 6-6 9-9 12-4 15-1 17-6 5-11 8-8 11-0 13-6 15-7
Spruce-pine-fir                        #3 5-0 7-4 9-4 11-5 13-2 4-6 6-7 8-4 10-2 11-10
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
  1. Span exceeds 26 feet in length.



TABLE R802.5.1(6)
RAFTER SPANS FOR COMMON LUMBER SPECIES
(Ground snow load = 50 psf, ceiling attached to rafters, L/Δ = 240)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
7-8 12-1 15-11 20-3 24-8 7-8 12-1 15-11 20-3 24-5
Douglas fir-larch                     #1
7-5 11-7 15-3 18-7 21-7 7-5 11-2 14-1 17-3 20-0
Douglas fir-larch                     #2
7-3 11-5 14-5 17-8 20-5 7-3 10-7 13-4 16-4 18-11
Douglas fir-larch                     #3
6-0 8-9 11-0 13-6 15-7 5-6 8-1 10-3 12-6 14-6
Hem-fir                                    SS
7-3 11-5 15-0 19-2 23-4 7-3 11-5 15-0 19-2 23-4
Hem-fir                                    #1
7-1 11-2 14-8 18-4 21-3 7-1 11-0 13-11 17-0 19-9
Hem-fir                                    #2
6-9 10-8 14-0 17-2 19-11 6-9 10-3 13-0 15-10 18-5
Hem-fir                                    #3
5-10 8-6 10-9 13-2 15-3 5-5 7-10 10-0 12-2 14-1
Southern pine                         SS
7-6 11-10 15-7 19-11 24-3 7-6 11-10 15-7 19-11 24-3
Southern pine                         #1
7-3 11-5 15-0 18-2 21-7 7-3 11-4 14-5 16-10 20-0
Southern pine                         #2
6-11 10-6 13-4 15-10 18-8 6-6 9-9 12-4 14-8 17-3
Southern pine                         #3
5-5 8-0 10-1 12-3 14-6 5-0 7-5 9-4 11-4 13-5
Spruce-pine-fir                        SS
7-1 11-2 14-8 18-9 22-10 7-1 11-2 14-8 18-9 22-4
Spruce-pine-fir                        #1
6-11 10-11 14-3 17-5 20-2 6-11 10-5 13-2 16-1 18-8
Spruce-pine-fir                        #2
6-11 10-11 14-3 17-5 20-2 6-11 10-5 13-2 16-1 18-8
Spruce-pine-fir                        #3
5-10 8-6 10-9 13-2 15-3 5-5 7-10 10-0 12-2 14-1
16 Douglas fir-larch                     SS
7-0 11-0 14-5 18-5 22-5 7-0 11-0 14-5 18-3 21-2
Douglas fir-larch                     #1
6-9 10-5 13-2 16-1 18-8 6-7 9-8 12-2 14-11 17-3
Douglas fir-larch                     #2 6-7 9-10 12-6 15-3 17-9 6-3 9-2 11-7 14-2 16-5
Douglas fir-larch                     #3 5-2 7-7 9-7 11-8 13-6 4-9 7-0 8-10 10-10 12-6
Hem-fir                                    SS
6-7 10-4 13-8 17-5 21-2 6-7 10-4 13-8 17-5 20-5
Hem-fir                                    #1 6-5 10-2 13-0 15-11 18-5 6-5 9-6 12-1 14-9 17-1
Hem-fir                                    #2 6-2 9-7 12-2 14-10 17-3 6-1 8-11 11-3 13-9 15-11
Hem-fir                                    #3 5-0 7-4 9-4 11-5 13-2 4-8 6-10 8-8 10-6 12-3
Southern pine                         SS
6-10 10-9 14-2 18-1 22-0 6-10 10-9 14-2 18-1 21-10
Southern pine                         #1 6-7 10-4 13-5 15-9 18-8 6-7 9-10 12-5 14-7 17-3
Southern pine                         #2 6-1 9-2 11-7 13-9 16-2 5-8 8-5 10-9 12-9 15-0
Southern pine                         #3 4-8 6-11 8-9 10-7 12-6 4-4 6-5 8-1 9-10 11-7
Spruce-pine-fir                        SS
6-5 10-2 13-4 17-0 20-9 6-5 10-2 13-4 16-8 19-4
Spruce-pine-fir                        #1 6-4 9-9 12-4 15-1 17-6 6-2 9-0 11-5 13-11 16-2
Spruce-pine-fir                        #2 6-4 9-9 12-4 15-1 17-6 6-2 9-0 11-5 13-11 16-2
Spruce-pine-fir                        #3 5-0 7-4 9-4 11-5 13-2 4-8 6-10 8-8 10-6 12-3
19.2 Douglas fir-larch                     SS
6-7 10-4 13-7 17-4 20-11 6-7 10-4 13-7 16-8 19-4
Douglas fir-larch                     #1 6-4 9-6 12-0 14-8 17-1 6-0 8-10 11-2 13-7 15-9
Douglas fir-larch                     #2 6-2 9-0 11-5 13-11 16-2 5-8 8-4 10-7 12-11 15-0
Douglas fir-larch                     #3 4-8 6-11 8-9 10-8 12-4 4-4 6-4 8-1 9-10 11-5
Hem-fir                                    SS
6-2 9-9 12-10 16-5 19-11 6-2 9-9 12-10 16-1 18-8
Hem-fir                                    #1 6-1 9-5 11-11 14-6 16-10 5-11 8-8 11-0 13-5 15-7
Hem-fir                                    #2 5-9 8-9 11-1 13-7 15-9 5-7 8-1 10-3 12-7 14-7
Hem-fir                                    #3 4-7 6-9 8-6 10-5 12-1 4-3 6-3 7-11 9-7 11-2
Southern pine                         SS
6-5 10-2 13-4 17-0 20-9 6-5 10-2 13-4 16-11 20-0
Southern pine                         #1 6-2 9-8 12-3 14-4 17-1 6-0 9-0 11-4 13-4 15-9
Southern pine                         #2 5-7 8-4 10-7 12-6 14-9 5-2 7-9 9-9 11-7 13-8
Southern pine                         #3 4-3 6-4 8-0 9-8 11-5 4-0 5-10 7-4 8-11 10-7
Spruce-pine-fir                        SS
6-1 9-6 12-7 16-0 19-1 6-1 9-6 12-5 15-3 17-8
Spruce-pine-fir                        #1 5-11 8-11 11-3 13-9 15-11 5-7 8-3 10-5 12-9 14-9
Spruce-pine-fir                        #2 5-11 8-11 11-3 13-9 15-11 5-7 8-3 10-5 12-9 14-9
Spruce-pine-fir                        #3 4-7 6-9 8-6 10-5 12-1 4-3 6-3 7-11 9-7 11-2
24 Douglas fir-larch                     SS
6-1 9-7 12-7 16-1 18-8 6-1 9-7 12-2 14-11 17-3
Douglas fir-larch                     #1 5-10 8-6 10-9 13-2 15-3 5-5 7-10 10-0 12-2 14-1
Douglas fir-larch                     #2 5-6 8-1 10-3 12-6 14-6 5-1 7-6 9-5 11-7 13-5
Douglas fir-larch                     #3 4-3 6-2 7-10 9-6 11-1 3-11 5-8 7-3 8-10 10-3
Hem-fir                                    SS
5-9 9-1 11-11 15-2 18-0 5-9 9-1 11-9 14-5 15-11
Hem-fir                                    #1 5-8 8-5 10-8 13-0 15-1 5-4 7-9 9-10 12-0 13-11
Hem-fir                                    #2 5-4 7-10 9-11 12-1 14-1 4-11 7-3 9-2 11-3 13-0
Hem-fir                                    #3 4-1 6-0 7-7 9-4 10-9 3-10 5-7 7-1 8-7 10-0
Southern pine                         SS
6-0 9-5 12-5 15-10 19-3 6-0 9-5 12-5 15-2 17-10
Southern pine                         #1 5-9 8-8 11-0 12-10 15-3 5-5 8-0 10-2 11-11 14-1
Southern pine                         #2 5-0 7-5 9-5 11-3 13-2 4-7 6-11 8-9 10-5 12-3
Southern pine                         #3 3-10 5-8 7-1 8-8 10-3 3-6 5-3 6-7 8-0 9-6
Spruce-pine-fir                        SS
5-8 8-10 11-8 14-8 17-1 5-8 8-10 11-2 13-7 15-9
Spruce-pine-fir                        #1 5-5 7-11 10-1 12-4 14-3 5-0 7-4 9-4 11-5 13-2
Spruce-pine-fir                        #2 5-5 7-11 10-1 12-4 14-3 5-0 7-4 9-4 11-5 13-2
Spruce-pine-fir                        #3 4-1 6-0 7-7 9-4 10-9 3-10 5-7 7-1 8-7 10-0
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.



TABLE R802.5.1(7)
RAFTER SPANS FOR 70 PSF GROUND SNOW LOAD
(Ceiling not attached to rafters, L/Δ = 180)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
7-7 11-10 15-8 19-9 22-10 7-7 11-10 15-3 18-7 21-7
Douglas fir-larch                     #1
7-1 10-5 13-2 16-1 18-8 6-8 9-10 12-5 15-2 17-7
Douglas fir-larch                     #2
6-9 9-10 12-6 15-3 17-9 6-4 9-4 11-9 14-5 16-8
Douglas fir-larch                     #3
5-2 7-7 9-7 11-8 13-6 4-10 7-1 9-0 11-0 12-9
Hem-fir                                    SS
7-2 11-3 14-9 18-10 22-1 7-2 11-3 14-8 18-0 20-10
Hem-fir                                    #1
7-0 10-3 13-0 15-11 18-5 6-7 9-8 12-3 15-0 17-5
Hem-fir                                    #2
6-7 9-7 12-2 14-10 17-3 6-2 9-1 11-5 14-0 16-3
Hem-fir                                    #3
5-0 7-4 9-4 11-5 13-2 4-9 6-11 8-9 10-9 12-5
Southern pine                         SS
7-5 11-8 15-4 19-7 23-7 7-5 11-8 15-4 18-10 22-3
Southern pine                         #1
7-1 10-7 13-5 15-9 18-8 6-9 10-0 12-8 14-10 17-7
Southern pine                         #2
6-1 9-2 11-7 13-9 16-2 5-9 8-7 10-11 12-11 15-3
Southern pine                         #3
4-8 6-11 8-9 10-7 12-6 4-5 6-6 8-3 10-0 11-10
Spruce-pine-fir                        SS
7-0 11-0 14-6 18-0 20-11 7-0 11-0 13-11 17-0 19-8
Spruce-pine-fir                        #1
6-8 9-9 12-4 15-1 17-6 6-3 9-2 11-8 14-2 16-6
Spruce-pine-fir                        #2
6-8 9-9 12-4 15-1 17-6 6-3 9-2 11-8 14-2 16-6
Spruce-pine-fir                        #3
5-0 7-4 9-4 11-5 13-2 4-9 6-11 8-9 10-9 12-5
16 Douglas fir-larch                     SS
6-10 10-9 14-0 17-1 19-10 6-10 10-5 13-2 16-1 18-8
Douglas fir-larch                     #1
6-2 9-0 11-5 13-11 16-2 5-10 8-6 10-9 13-2 15-3
Douglas fir-larch                     #2 5-10 8-7 10-10 13-3 15-4 5-6 8-1 10-3 12-6 14-6
Douglas fir-larch                     #3 4-6 6-6 8-3 10-1 11-9 4-3 6-2 7-10 9-6 11-1
Hem-fir                                    SS
6-6 10-2 13-5 16-6 19-2 6-6 10-1 12-9 15-7 18-0
Hem-fir                                    #1 6-1 8-11 11-3 13-9 16-0 5-9 8-5 10-8 13-0 15-1
Hem-fir                                    #2 5-8 8-4 10-6 12-10 14-11 5-4 7-10 9-11 12-1 14-1
Hem-fir                                    #3 4-4 6-4 8-1 9-10 11-5 4-1 6-0 7-7 9-4 10-9
Southern pine                         SS
6-9 10-7 14-0 17-4 20-5 6-9 10-7 13-9 16-4 19-3
Southern pine                         #1 6-2 9-2 11-8 13-8 16-2 5-10 8-8 11-0 12-10 15-3
Southern pine                         #2 5-3 7-11 10-0 11-11 14-0 5-0 7-5 9-5 11-3 13-2
Southern pine                         #3 4-1 6-0 7-7 9-2 10-10 3-10 5-8 7-1 8-8 10-3
Spruce-pine-fir                        SS
6-4 10-0 12-9 15-7 18-1 6-4 9-6 12-0 14-8 17-1
Spruce-pine-fir                        #1 5-9 8-5 10-8 13-1 15-2 5-5 7-11 10-1 12-4 14-3
Spruce-pine-fir                        #2 5-9 8-5 10-8 13-1 15-2 5-5 7-11 10-1 12-4 14-3
Spruce-pine-fir                        #3 4-4 6-4 8-1 9-10 11-5 4-1 6-0 7-7 9-4 10-9
19.2 Douglas fir-larch                     SS
6-6 10-1 12-9 15-7 18-1 6-6 9-6 12-0 14-8 17-1
Douglas fir-larch                     #1 5-7 8-3 10-5 12-9 14-9 5-4 7-9 9-10 12-0 13-11
Douglas fir-larch                     #2 5-4 7-10 9-11 12-1 14-0 5-0 7-4 9-4 11-5 13-2
Douglas fir-larch                     #3 4-1 6-0 7-7 9-3 10-8 3-10 5-7 7-1 8-8 10-1
Hem-fir                                    SS
6-1 9-7 12-4 15-1 17-4 6-1 9-2 11-8 14-2 15-5
Hem-fir                                    #1 5-7 8-2 10-3 12-7 14-7 5-3 7-8 9-8 11-10 13-9
Hem-fir                                    #2 5-2 7-7 9-7 11-9 13-7 4-11 7-2 9-1 11-1 12-10
Hem-fir                                    #3 4-0 5-10 7-4 9-0 10-5 3-9 5-6 6-11 8-6 9-10
Southern pine                         SS
6-4 10-0 13-2 15-10 18-8 6-4 9-10 12-6 14-11 17-7
Southern pine                         #1 5-8 8-5 10-8 12-5 14-9 5-4 7-11 10-0 11-9 13-11
Southern pine                         #2 4-10 7-3 9-2 10-10 12-9 4-6 6-10 8-8 10-3 12-1
Southern pine                         #3 3-8 5-6 6-11 8-4 9-11 3-6 5-2 6-6 7-11 9-4
Spruce-pine-fir                        SS
6-0 9-2 11-8 14-3 16-6 5-11 8-8 11-0 13-5 15-7
Spruce-pine-fir                        #1 5-3 7-8 9-9 11-11 13-10 5-0 7-3 9-2 11-3 13-0
Spruce-pine-fir                        #2 5-3 7-8 9-9 11-11 13-10 5-0 7-3 9-2 11-3 13-0
Spruce-pine-fir                        #3 4-0 5-10 7-4 9-0 10-5 3-9 5-6 6-11 8-6 9-10
24 Douglas fir-larch                     SS
6-0 9-0 11-5 13-11 16-2 5-10 8-6 10-9 13-2 15-3
Douglas fir-larch                     #1 5-0 7-4 9-4 11-5 13-2 4-9 6-11 8-9 10-9 12-5
Douglas fir-larch                     #2 4-9 7-0 8-10 10-10 12-6 4-6 6-7 8-4 10-2 11-10
Douglas fir-larch                     #3 3-8 5-4 6-9 8-3 9-7 3-5 5-0 6-4 7-9 9-10
Hem-fir                                    SS
5-8 8-8 11-0 13-6 13-11 5-7 8-3 10-5 12-4 12-4
Hem-fir                                    #1 5-0 7-3 9-2 11-3 13-0 4-8 6-10 8-8 10-7 12-4
Hem-fir                                    #2 4-8 6-9 8-7 10-6 12-2 4-4 6-5 8-1 9-11 11-6
Hem-fir                                    #3 3-7 5-2 6-7 8-l 9-4 3-4 4-11 6-3 7-7 8-10
Southern pine                         SS
5-11 9-3 11-11 14-2 16-8 5-11 8-10 11-2 13-4 15-9
Southern pine                         #1 5-0 7-6 9-6 11-1 13-2 4-9 7-1 9-0 10-6 12-5
Southern pine                         #2 4-4 6-5 8-2 9-9 11-5 4-1 6-1 7-9 9-2 10-9
Southern pine                         #3 3-4 4-11 6-2 7-6 8-10 3-1 4-7 5-10 7-1 8-4
Spruce-pine-fir                        SS
5-6 8-3 10-5 12-9 14-9 5-4 7-9 9-10 12-0 12-11
Spruce-pine-fir                        #1 4-8 6-11 8-9 10-8 12-4 4-5 6-6 8-3 10-0 11-8
Spruce-pine-fir                        #2 4-8 6-11 8-9 10-8 12-4 4-5 6-6 8-3 10-0 11-8
Spruce-pine-fir                        #3 3-7 5-2 6-7 8-1 9-4 3-4 4-11 6-3 7-7 8-10
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.



TABLE R802.5.1(8)
RAFTER SPANS FOR 70 PSF GROUND SNOW LOAD
(Ceiling attached to rafters, L/Δ = 240)
RAFTER
SPACING
(inches)
SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 x 4
2 x 6
2 x 8
2 x 10
2 x 12 2 x 4
2 x 6
2 x 8
2 x 10 2 x 12
Maximum rafter spansa
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
(feet -
inches)
12 Douglas fir-larch                     SS
6-10 10-9 14-3 18-2 22-1 6-10 10-9 14-3 18-2 21-7
Douglas fir-larch                     #1
6-7 10-5 13-2 16-1 18-8 6-7 9-10 12-5 15-2 17-7
Douglas fir-larch                     #2
6-6 9-10 12-6 15-3 17-9 6-4 9-4 11-9 14-5 16-8
Douglas fir-larch                     #3
5-2 7-7 9-7 11-8 13-6 4-10 7-1 9-0 11-0 12-9
Hem-fir                                    SS
6-6 10-2 13-5 17-2 20-10 6-6 10-2 13-5 17-2 20-10
Hem-fir                                    #1
6-4 10-0 13-0 15-11 18-5 6-4 9-8 12-3 15-0 17-5
Hem-fir                                    #2
6-1 9-6 12-2 14-10 17-3 6-1 9-1 11-5 14-0 16-3
Hem-fir                                    #3
5-0 7-4 9-4 11-5 13-2 4-9 6-11 8-9 10-9 12-5
Southern pine                         SS
6-9 10-7 14-0 17-10 21-8 6-9 10-7 14-0 17-10 21-8
Southern pine                         #1
6-6 10-2 13-5 15-9 18-8 6-6 10-0 12-8 14-10 17-7
Southern pine                         #2
6-1 9-2 11-7 13-9 16-2 5-9 8-7 10-11 12-11 15-3
Southern pine                         #3
4-8 6-11 8-9 10-7 12-6 4-5 6-6 8-3 10-0 11-10
Spruce-pine-fir                        SS
6-4 10-0 13-2 16-9 20-5 6-4 10-0 13-2 16-9 19-8
Spruce-pine-fir                        #1
6-2 9-9 12-4 15-1 17-6 6-2 9-2 11-8 14-2 16-6
Spruce-pine-fir                        #2
6-2 9-9 12-4 15-1 17-6 6-2 9-2 11-8 14-2 16-6
Spruce-pine-fir                        #3
5-0 7-4 9-4 11-5 13-2 4-9 6-11 8-9 10-9 12-5
16 Douglas fir-larch                     SS
6-3 9-10 12-11 16-6 19-10 6-3 9-10 12-11 16-1 18-8
Douglas fir-larch                     #1
6-0 9-0 11-5 13-11 16-2 5-10 8-6 10-9 13-2 15-3
Douglas fir-larch                     #2 5-10 8-7 10-10 13-3 15-4 5-6 8-1 10-3 12-6 14-6
Douglas fir-larch                     #3 4-6 6-6 8-3 10-1 11-9 4-3 6-2 7-10 9-6 11-1
Hem-fir                                    SS
5-11 9-3 12-2 15-7 18-11 5-11 9-3 12-2 15-7 18-0
Hem-fir                                    #1 5-9 8-11 11-3 13-9 16-0 5-9 8-5 10-8 13-0 15-1
Hem-fir                                    #2 5-6 8-4 10-6 12-10 14-11 5-4 7-10 9-11 12-1 14-1
Hem-fir                                    #3 4-4 6-4 8-1 9-10 11-5 4-1 6-0 7-7 9-4 10-9
Southern pine                         SS
6-1 9-7 12-8 16-2 19-8 6-1 9-7 12-8 16-2 19-3
Southern pine                         #1 5-11 9-2 11-8 13-8 16-2 5-10 8-8 11-0 12-10 15-3
Southern pine                         #2 5-3 7-11 10-0 11-11 14-0 5-0 7-5 9-5 11-3 13-2
Southern pine                         #3 4-1 6-0 7-7 9-2 10-10 3-10 5-8 7-1 8-8 10-3
Spruce-pine-fir                        SS
5-9 9-1 11-11 15-3 18-1 5-9 9-1 11-11 14-8 17-1
Spruce-pine-fir                        #1 5-8 8-5 10-8 13-1 15-2 5-5 7-11 10-1 12-4 14-3
Spruce-pine-fir                        #2 5-8 8-5 10-8 13-1 15-2 5-5 7-11 10-1 12-4 14-3
Spruce-pine-fir                        #3 4-4 6-4 8-1 9-10 11-5 4-1 6-0 7-7 9-4 10-9
19.2 Douglas fir-larch                     SS
5-10 9-3 12-2 15-6 18-1 5-10 9-3 12-0 14-8 17-1
Douglas fir-larch                     #1 5-7 8-3 10-5 12-9 14-9 5-4 7-9 9-10 12-0 13-11
Douglas fir-larch                     #2 5-4 7-10 9-11 12-1 14-0 5-0 7-4 9-4 11-5 13-2
Douglas fir-larch                     #3 4-1 6-0 7-7 9-3 10-8 3-10 5-7 7-1 8-8 10-1
Hem-fir                                    SS
5-6 8-8 11-6 14-8 17-4 5-6 8-8 11-6 14-2 15-5
Hem-fir                                    #1 5-5 8-2 10-3 12-7 14-7 5-3 7-8 9-8 11-10 13-9
Hem-fir                                    #2 5-2 7-7 9-7 11-9 13-7 4-11 7-2 9-1 11-1 12-10
Hem-fir                                    #3 4-0 5-10 7-4 9-0 10-5 3-9 5-6 6-11 8-6 9-10
Southern pine                         SS
5-9 9-1 11-11 15-3 18-6 5-9 9-1 11-11 14-11 17-7
Southern pine                         #1 5-6 8-5 10-8 12-5 14-9 5-4 7-11 10-0 11-9 13-11
Southern pine                         #2 4-10 7-3 9-2 10-10 12-9 4-6 6-10 8-8 10-3 12-1
Southern pine                         #3 3-8 5-6 6-11 8-4 9-11 3-6 5-2 6-6 7-11 9-4
Spruce-pine-fir                        SS
5-5 8-6 11-3 14-3 16-6 5-5 8-6 11-0 13-5 15-7
Spruce-pine-fir                        #1 5-3 7-8 9-9 11-11 13-10 5-0 7-3 9-2 11-3 13-0
Spruce-pine-fir                        #2 5-3 7-8 9-9 11-11 13-10 5-0 7-3 9-2 11-3 13-0
Spruce-pine-fir                        #3 4-0 5-10 7-4 9-0 10-5 3-9 5-6 6-11 8-6 9-10
24 Douglas fir-larch                     SS
5-5 8-7 11-3 13-11 16-2 5-5 8-6 10-9 13-2 15-3
Douglas fir-larch                     #1 5-0 7-4 9-4 11-5 13-2 4-9 6-11 8-9 10-9 12-5
Douglas fir-larch                     #2 4-9 7-0 8-10 10-10 12-6 4-6 6-7 8-4 10-2 11-10
Douglas fir-larch                     #3 3-8 5-4 6-9 8-3 9-7 3-5 5-0 6-4 7-9 9-0
Hem-fir                                    SS
5-2 8-1 10-8 13-6 13-11 5-2 8-1 10-5 12-4 12-4
Hem-fir                                    #1 5-0 7-3 9-2 11-3 13-0 4-8 6-10 8-8 10-7 12-4
Hem-fir                                    #2 4-8 6-9 8-7 10-6 12-2 4-4 6-5 8-1 9-11 11-6
Hem-fir                                    #3 3-7 5-2 6-7 8-1 9-4 3-4 4-11 6-3 7-7 8-10
Southern pine                         SS
5-4 8-5 11-1 14-2 16-8 5-4 8-5 11-1 13-4 15-9
Southern pine                         #1 5-0 7-6 9-6 11-1 13-2 4-9 7-1 9-0 10-6 12-5
Southern pine                         #2 4-4 6-5 8-2 9-9 11-5 4-1 6-1 7-9 9-2 10-9
Southern pine                         #3 3-4 4-11 6-2 7-6 8-10 3-1 4-7 5-10 7-1 8-4
Spruce-pine-fir                        SS
5-0 7-11 10-5 12-9 14-9 5-0 7-9 9-10 12-0 12-11
Spruce-pine-fir                        #1 4-8 6-11 8-9 10-8 12-4 4-5 6-6 8-3 10-0 11-8
Spruce-pine-fir                        #2 4-8 6-11 8-9 10-8 12-4 4-5 6-6 8-3 10-0 11-8
Spruce-pine-fir                        #3 3-7 5-2 6-7 8-1 9-4 3-4 4-11 6-3 7-7 8-10
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor
1/3
1/4
1/5
1/6
1/7.5 or less
0.67
0.76
0.83
0.90
1.00

where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.



Installation of purlins to reduce the span of rafters is permitted as shown in Figure R802.5.1. Purlins shall be sized not less than the required size of the rafters that they support. Purlins shall be continuous and shall be supported by 2-inch by 4-inch (51 mm by 102 mm) braces installed to bearing walls at a slope not less than 45 degrees (0.79 rad) from the horizontal. The braces shall be spaced not more than 4 feet (1219 mm) on center and the unbraced length of braces shall not exceed 8 feet (2438 mm).
For SI: 1 inch = 25.4 mm, 1 foot = 305 mm, 1 degree = 0.018 rad.

Note: Where ceiling joist s run perpendicular to the rafter, rafter ties shall be installed in accordance with Section R802.3.1.
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
FIGURE R802.5.1
BRACED RAFTER CONSTRUCTION
The ends of each rafter or ceiling joist shall have not less than 1½ inches (38 mm) of bearing on wood or metal and not less than 3 inches (76 mm) on masonry or concrete. The bearing on masonry or concrete shall be direct, or a sill plate of 2-inch (51 mm) minimum nominal thickness shall be provided under the rafter or ceiling joist. The sill plate shall provide a minimum nominal bearing area of 48 square inches (30865 mm2).
If the finished ceiling material is installed on the ceiling prior to the attachment of the ceiling to the walls, such as in construction at a factory, a compression strip of the same thickness as the finished ceiling material shall be installed directly above the top plate of bearing walls if the compressive strength of the finished ceiling material is less than the loads it will be required to withstand. The compression strip shall cover the entire length of such top plate and shall be not less than one-half the width of the top plate. It shall be of material capable of transmitting the loads transferred through it.
Structural roof members shall not be cut, bored or notched in excess of the limitations specified in this section.
Cuts, notches and holes in solid lumber joists, rafters, blocking and beams shall comply with the provisions of Section R502.8.1 except that cantilevered portions of rafters shall be permitted in accordance with Section R802.7.1.1.
Notches on cantilevered portions of rafters are permitted provided the dimension of the remaining portion of the rafter is not less than 3½ inches (89 mm) and the length of the cantilever does not exceed 24 inches (610 mm) in accordance with Figure R802.7.1.1.
For SI: 1 inch= 25.4 mm.
FIGURE R802.7.1.1
RAFTER NOTCH
Taper cuts at the ends of the ceiling joist shall not exceed one-fourth the depth of the member in accordance with Figure R802.7.1.2.
FIGURE R802.7.1.2
CEILING JOIST TAPER CUT
Cuts, notches and holes bored in trusses, structural composite lumber, structural glue-laminated members, cross-laminated timber members or I-joists are prohibited except where permitted by the manufacturer's recommendations or where the effects of such alterations are specifically considered in the design of the member by a registered design professional.
Roof framing members and ceiling joists having a depth-to-thickness ratio exceeding 5 to 1 based on nominal dimensions shall be provided with lateral support at points of bearing to prevent rotation. For roof rafters with ceiling joists attached in accordance with Table R602.3(1), the depth-to-thickness ratio for the total assembly shall be determined using the combined thickness of the rafter plus the attached ceiling joist.

Exception: Roof trusses shall be braced in accordance with Section R802.10.3.
Rafters and ceiling joists having a depth-to-thickness ratio exceeding 6 to 1 based on nominal dimensions shall be supported laterally by solid blocking, diagonal bridging (wood or metal) or a continuous 1-inch by 3-inch (25 mm by 76 mm) wood strip nailed across the rafters or ceiling joists at intervals not exceeding 8 feet (2438 mm).
Openings in roof and ceiling framing shall be framed with header and trimmer joists. Where the header joist span does not exceed 4 feet (1219 mm), the header joist shall be permitted to be a single member the same size as the ceiling joist or rafter. Single trimmer joists shall be permitted to be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing. Where the header joist span exceeds 4 feet (1219 mm), the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the ceiling joists or rafter framing into the header. Approved hangers shall be used for the header joist to trimmer joist connections where the header joist span exceeds 6 feet (1829 mm). Tail joists over 12 feet (3658 mm) long shall be supported at the header by framing anchors or on ledger strips not less than 2 inches by 2 inches (51 mm by 51 mm).
Truss design drawings, prepared in conformance with Section R802.10.1, shall be provided to the building official and approved prior to installation. The truss design data sheet, Figure R802.10.1, may be provided to the building official at the time of permit application, as an alternative to design drawings as permitted in Section R106.1.4. Truss design drawings shall include, at a minimum, the information specified below. Truss design drawings shall be provided with the shipment of trusses delivered to the jobsite.
  1. Slope or depth, span, and spacing.
  2. Location of all joints.
  3. Required bearing widths.
  4. Design loads as applicable.

    1. Top chord live load (including snow loads).
    2. Top chord dead load.
    3. Bottom chord live load.
    4. Bottom chord dead load.
    5. Concentrated loads and their points of application.
    6. Controlling wind and earthquake loads.
  5. Adjustments to lumber and joint connector design values for conditions of use.
  6. Each reaction force and direction.
  7. Joint connector type and description (e.g., size, thickness, or gauge) and the dimensioned location of each joint connector except where symmetrically located relative to the joint interface.
  8. Lumber size, species, and grade for each member.
  9. Connection requirements for the following:

    1. Truss to truss girder.
    2. Truss ply to ply.
    3. Field splices.
  10. Calculated deflection ratio and/or maximum description for live and total load.
  11. Maximum axial compression forces in the truss members to enable the building designer to design the size, connections, and anchorage of the permanent continuous lateral bracing. Forces shall be shown on the truss design drawing or on supplemental documents.
  12. Required permanent truss member bracing location.

   Where prescriptive design is used, the ground snow load, Pg, from Table R301.2(1) shall be used as the design roof snow except, where section R802.10.2.1 applies the design roof snow load shall be.7Pg. Additional unbalanced loads for drifting across the ridge are not required. Where engineered design is used, this form is to be completed by the permit applicant or design professional. The flat roof snow load, Pf is defined as: Pf=.7Pg(Ce)(Ct)(I). For factors Ce, Ct, and I, place an "X" in the appropriate box below that best describes the structure and the particular jobsite and substitute the corresponding values in the formula above. The result is the flat roof snow load and is applied as the truss top chord live load, TCLL1. All live loads and snow loads, including unbalanced loads and minimum loads, are to be applied per ASCE 7, chapters 4 and 7 and this code.

1   Fully Exposed: Roofs exposed on all sides with no shelter by terrain, higher structures, or trees.
2   Partially Exposed: All roofs except those designated as "fully exposed" or "sheltered."
3   Sheltered: Roofs located tight among conifers that qualify as obstructions.
Note: All roof trusses have additional live (storage) loads applied to the bottom chord where required per Table R301.5.
FIGURE 802.10.1
ROOF LOADING DATA SHEET
Wood trusses shall be designed in accordance with accepted engineering practice. The design and manufacture of metal-plate-connected wood trusses shall comply with ANSI/TPI 1. The truss design drawings shall be prepared by a registered professional where required by the statutes of the jurisdiction in which the project is to be constructed in accordance with Section R106.1.
The provisions of this section shall control the design of truss roof framing when snow controls for buildings, not greater than 60 feet (18288 mm) in length perpendicular to the joist, rafter or truss span, not greater than 36 feet (10973 mm) in width parallel to the joist, rafter or truss span, not more than three stories above grade plane in height, and roof slopes not smaller than 3:12 (25 percent slope) or greater than 12:12 (100-percent slope). Truss roof framing constructed in accordance with the provision s of this section shall be limited to sites subjected to a maximum design wind speed of 140 miles per hour (63 m/s), Exposure B or C, and a maximum ground snow load of 70 psf (3352 Pa). For consistent loading of all truss types, roof snow load is to be computed as: 0.7 pg.
Trusses shall be braced to prevent rotation and provide lateral stability in accordance with the requirements specified in the construction documents for the building and on the individual truss design drawings. In the absence of specific bracing requirements, trusses shall be braced in accordance with accepted industry practice such as the SBCA Building Component Safety Information (BCSI) Guide to Good Practice for Handling, Installing & Bracing of Metal Plate Connected Wood Trusses.
Truss members shall not be cut, notched, drilled, spliced or otherwise altered in any way without the approval of a registered design professional. Alterations resulting in the addition of load such as HVAC equipment water heater that exceeds the design load for the truss shall not be permitted without verification that the truss is capable of supporting such additional loading.
Roof assemblies shall have uplift resistance in accordance with Sections R802.11.1.1 and R802.11.1.2.

     Where the uplift force does not exceed 200 pounds (90.8 kg), rafters and trusses spaced not more than 24 inches (610 mm) on center shall be permitted to be attached to their supporting wall assemblies in accordance with Table R602.3(1).

     Where the basic wind speed does not exceed 115 mph, the wind exposure category is B, the roof pitch is 5:12 or greater, and the roof span is 32 feet (9754 mm) or less, rafters and trusses spaced not more than 24 inches (610 mm) on center shall be permitted to be attached to their supporting wall assemblies in accordance with Table R602.3(1).
Trusses shall be attached to supporting wall assemblies by connections capable of resisting uplift forces as specified on the truss design drawings for the ultimate design wind speed as determined by Figure R301.2(4)A and listed in Table R301.2(1) or as shown on the construction documents. Uplift forces shall be permitted to be determined as specified by Table R802.11, if applicable, or as determined by accepted engineering practice.

TABLE R802.11
RAFTER OR TRUSS UPLIFT CONNECTION FORCES FROM WIND (ASD) (POUNDS PER CONNECTION)a, b, c, d, e, f, g, h
RAFTER
OR TRUSS
SPACING
ROOF
SPAN
(feet)
EXPOSURE B
Ultimate Design Wind Speed VULT (mph)
110 115 120 130 140
Roof Pitch Roof Pitch Roof Pitch Roof Pitch Roof Pitch
< 5:12
≥ 5:12
< 5:12 ≥ 5:12 < 5:12 ≥ 5:12 < 5:12 ≥ 5:12 < 5:12 ≥ 5:12
12" o.c.
12 48 43 59 53 70 64 95 88 122 113
18 59 52 74 66 89 81 122 112 157 146
24 71 62 89 79 108 98 149 137 192 178
28 79 69 99 88 121 109 167 153 216 200
32 86 75 109 97 134 120 185 170 240 222
36 94 82 120 106 146 132 203 186 264 244
42 106 92 135 120 166 149 230 211 300 278
48 118 102 151 134 185 166 258 236 336 311
16" o.c. 12 64 57 78 70 93 85 126 117 162 150
18 78 69 98 88 118 108 162 149 209 194
24 94 82 118 105 144 130 198 182 255 237
28 105 92 132 117 161 145 222 203 287 266
32 114 100 145 129 178 160 246 226 319 295
36 125 109 160 141 194 176 270 247 351 325
42 141 122 180 160 221 198 306 281 399 370
48 157 136 201 178 246 221 343 314 447 414
24" o.c. 12 96 86 118 106 140 128 190 176 244 226
18 118 104 148 132 178 162 244 224 314 292
24 142 124 178 158 216 196 298 274 384 356
28 158 138 198 176 242 218 334 306 432 400
32 172 150 218 194 268 240 370 340 480 444
36 188 164 240 212 292 264 406 372 528 488
42 212 184 270 240 332 298 460 422 600 556
48 236 204 302 268 370 332 516 472 672 622


TABLE R802.11--continued
RAFTER OR TRUSS UPLIFT CONNECTION FORCES FROM WIND (POUNDS PER CONNECTION)a, b, c, d, e, f, g, h
RAFTER
OR TRUSS
SPACING
ROOF
SPAN
(feet)
EXPOSURE C
Ultimate Design Wind Speed VULT (mph)
110 115 120 130 140
Roof Pitch Roof Pitch Roof Pitch Roof Pitch Roof Pitch
< 5:12
≥ 5:12
< 5:12 ≥ 5:12 < 5:12 ≥ 5:12 < 5:12 ≥ 5:12 < 5:12 ≥ 5:12
12" o.c.
12 95 88 110 102 126 118 161 151 198 186
18 121 111 141 131 163 151 208 195 257 242
24 148 136 173 160 200 185 256 239 317 298
28 166 152 195 179 225 208 289 269 358 335
32 184 168 216 199 249 231 321 299 398 373
36 202 185 237 219 274 254 353 329 438 411
42 229 210 269 248 312 289 402 375 499 468
48 256 234 302 278 349 323 450 420 560 524
16" o.c. 12 126 117 146 136 168 157 214 201 263 247
18 161 148 188 174 217 201 277 259 342 322
24 197 181 230 213 266 246 340 318 422 396
28 221 202 259 238 299 277 384 358 476 446
32 245 223 287 265 331 307 427 398 529 496
36 269 246 315 291 364 338 469 438 583 547
42 305 279 358 330 415 384 535 499 664 622
48 340 311 402 370 464 430 599 559 745 697
24" o.c. 12 190 176 220 204 252 236 322 302 396 372
18 242 222 282 262 326 302 416 390 514 484
24 296 272 346 320 400 370 512 478 634 596
28 332 304 390 358 450 416 578 538 716 670
32 368 336 432 398 498 462 642 598 796 746
36 404 370 474 438 548 508 706 658 876 822
42 458 420 538 496 624 578 804 750 998 936
48 512 468 604 556 698 646 900 840 1120 1048
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 mile per hour= 0.447 m/s, 1 pound= 0.454 kg, 1 pound per square foot= 47.9 N/m2, 1 plf = 14.6 N/m.
  1. The uplift connection forces are based on a maximum 33-foot mean roof height and Wind Exposure Category B or C. For Exposure D, the uplift connection force shall be selected from the Exposure C portion of the table using the next highest tabulated ultimate design wind speed. The adjustment coefficients in Table R301.2(3) shall not be used to multiply the tabulated forces for Exposures C and D or for other mean roof heights.
  2. The uplift connection forces include an allowance for roof and ceiling assembly dead load of 15 psf.
  3. The tabulated uplift connection forces are limited to a maximum roof overhang of 24 inches.
  4. The tabulated uplift connection forces shall be permitted to be multiplied by 0.75 for connections not located within 8 feet of building corners.
  5. For buildings with hip roofs with 5:12 and greater pitch, the tabulated uplift connection forces shall be permitted to be multiplied by 0.70. This reduction shall not be combined with any other reduction in tabulated forces.
  6. For wall-to-wall and wall-to-foundation connections, the uplift connection force shall be permitted to be reduced by 60 plf for each full wall above.
  7. Linear interpolation between tabulated roof spans and wind speeds shall be permitted.
  8. The tabulated forces for a 12-inch on-center spacing shall be permitted to be used to determine the uplift load in pounds per linear foot.
Individual rafters shall be attached to supporting wall assemblies by connections capable of resisting uplift forces as determined by Table R802.11 or as determined by accepted engineering practice. Connections for beams used in a roof system shall be designed in accordance with accepted engineering practice.
Allowable spans for lumber used as roof sheathing shall conform to Table R803.1. Spaced lumber sheathing for wood shingle and shake roofing shall conform to the requirements of Sections R905.7 and R905.8. Spaced lumber sheathing is not allowed in Seismic Design Category D2.

TABLE R803.1
MINIMUM THICKNESS OF LUMBER ROOF SHEATHING
RAFTER OR BEAM SPACING
(inches)
MINIMUM NET THICKNESS
(inches)
24
48a 1½ T & G
60b
72c
For SI: 1 inch = 25.4 mm.
  1. Minimum 270 Fb, 340,000 E.
  2. Minimum 420 Fb, 660,000 E.
  3. Minimum 600 Fb, 1,150,000 E.
Wood structural panels shall conform to DOC PS 1, DOC PS 2, CSA O437 or CSA O325, and shall be identified for grade, bond classification and performance category by a grade mark or certificate of inspection issued by an approved agency. Wood structural panels shall comply with the grades specified in Table R503.2.1.1(1).
Wood structural panels, when designed to be permanently exposed in outdoor applications, shall be of an exterior exposure durability. Wood structural panel roof sheathing exposed to the underside shall be permitted to be of interior type bonded with exterior glue, identified as Exposure 1.
The allowable unit stresses for fire-retardant-treated plywood, including fastener values, shall be developed from an approved method of investigation that considers the effects of anticipated temperature and humidity to which the fire-retardant-treated plywood will be subjected, the type of treatment and redrying process. The fire-retardant-treated plywood shall be graded by an approved agency.
The maximum allowable spans for wood structural panel roof sheathing shall not exceed the values set forth in Table R503.2.1.1(1), or APA E30.
Wood structural panel used as roof sheathing shall be installed with joints staggered or not staggered in accordance with Table R602.3(1), APA E30 for wood roof framing or with Table R804.3 for cold-formed steel roof framing.

TABLE R804.3
ROOF FRAMING FASTENING SCHEDULEa, b
DESCRIPTION OF BUILDING ELEMENTS NUMBER AND SIZE OF FASTENERSa SPACING OF FASTENERS
Roof sheathing (oriented strand board or
plywood) to rafter
No. 8 screws 6″ o.c. on edges and 12″ o.c. at interior supports. 6″ o.c. at gable end truss
Gable end truss to end wall top track No. 10 screws 12″ o.c.
Rafter to ceiling joist Minimum No. 10 screws,
in accordance with Table R804.3.1.1(3)
Evenly spaced, not less
than ½″ from all edges.
Ceiling joist or
roof truss to top
track of bearing wallb
Ceiling Joist
Spacing
(in.)
Roof Span
(ft)
Ultimate Design Wind Speed
(mph) and Exposure Category
Each ceiling joist
or roof truss
126 B
110 C
< 139 B
115 C
126 C < 139 C
16 24 2 2 2 3
28 2 2 3 3
32 2 2 3 4
36 2 2 3 4
40 2 2 3 4
24 24 2 2 3 4
28 2 2 4 5
32 2 3 4 5
36 2 3 4 6
40 2 3 5 6
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa, 1 mil= 0.0254 mm.
  1. Screws are a minimum No. 10 unless noted otherwise.
  2. Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle. See Section R804.3.8 for additional requirements to resist uplift forces.


TABLE R804.3.1.1(3)
NUMBER OF SCREWS REQUIRED FOR CEILING JOIST TO ROOF RAFTER CONNECTIONa
ROOF SLOPE NUMBER OF SCREWS
Building width (feet)
24 28 32 36 40
Ground snow load (psf)
20 30 50 70 20 30 50 70 20 30 50 70 20 30 50 70 20 30 50 70
3/12 5 6 9 11 5 7 10 13 6 8 11 15 7 8 13 17 8 9 14 19
4/12 4 5 7 9 4 5 8 10 5 6 9 12 5 7 10 13 6 7 11 14
5/12 3 4 6 7 4 4 6 8 4 5 7 10 5 5 8 11 5 6 9 12
6/12 3 3 5 6 3 4 6 7 4 4 6 8 4 5 7 9 4 5 8 10
7/12 3 3 4 6 3 3 5 7 3 4 6 7 4 4 6 8 4 5 7 9
8/12 2 3 4 5 3 3 5 6 3 4 5 7 3 4 6 8 4 4 6 8
9/12 2 3 4 5 3 3 4 6 3 3 5 6 3 4 5 7 3 4 6 8
10/12 2 2 4 5 2 3 4 5 3 3 5 6 3 3 5 7 3 4 6 7
11/12 2 2 3 4 2 3 4 5 3 3 4 6 3 3 5 6 3 4 5 7
12/12 2 2 3 4 2 3 4 5 2 3 4 5 3 3 5 6 3 4 5 7
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479kPa.
  1. Screws shall be No. 10.
Elements shall be straight and free of any defects that would significantly affect their structural performance. Cold-formed steel roof framing members shall be in accordance with the requirements of this section.
The provisions of this section shall control the construction of cold-formed steel roof framing for buildings not greater than 60 feet (18288 mm) perpendicular to the joist, rafter or truss span, not greater than 40 feet (12192 mm) in width parallel to the joist span or truss, less than or equal to three stories above grade plane and with roof slopes not less than 3:12 (25-percent slope) or greater than 12:12 (100-percent slope). Cold-formed steel roof framing constructed in accordance with the provisions of this section shall be limited to sites where the ultimate design wind speed is less than 139 miles per hour (62 m/s), Exposure Category B or C, and the ground snow load is less than or equal to 70 pounds per square foot (3350 Pa).
Cold-formed steel roof framing constructed in accordance with Section R804 shall be located in line with load-bearing studs in accordance with Figure R804.1.2 and the tolerances specified as follows:
  1. The maximum tolerance shall be ¾ inch (19.1 mm) between the centerline of the horizontal framing member and the centerline of the vertical framing member.
  2. Where the centerline of the horizontal framing member and bearing stiffener are located to one side of the centerline of the vertical framing member, the maximum tolerance shall be ⅛ inch (3.2 mm) between the web of the horizontal framing member and the edge of the vertical framing member.
For SI: 1 inch = 25.4 mm.
FIGURE R804.1.2
IN-LINE FRAMING
Load-bearing, cold-formed steel roof framing members shall be in accordance with this section.
Load-bearing, cold-formed steel framing members shall be cold formed to shape from structural quality sheet steel complying with the requirements of ASTM A1003, Structural Grades 33 Type H and 50 Type H.
Load-bearing, cold-formed steel framing shall have a metallic coating complying with ASTM A1003 and one of the following:
  1. A minimum of G 60 in accordance with ASTM A653.
  2. A minimum of AZ 50 in accordance with ASTM A792.
Load-bearing, cold-formed steel roof framing members shall comply with Figure R804.2.3(1) and with the dimensional and thickness requirements specified in Table R804.2.3. Additionally, C-shaped sections shall have a minimum flange width of 1.625 inches (41 mm) and a maximum flange width of 2 inches (51 mm). The minimum lip size for C-shaped sections shall be ½ inch (12.7 mm). Tracks shall comply with Figure R804.2.3(2) and shall have a minimum flange width of 1¼ inches (32 mm). Minimum Grade 33 ksi steel shall be used wherever 33 mil and 43 mil thicknesses are specified. Minimum Grade 50 ksi steel shall be used wherever 54 and 68 mil thicknesses are specified.

FIGURE R804.2.3(1)
C-SHAPED SECTION

FIGURE R804.2.3(2)
TRACK SECTION

TABLE R804.2.3
LOAD-BEARING COLD-FORMED STEEL ROOF FRAMING MEMBER SIZES AND THICKNESSES
MEMBER
DESIGNATIONa
WEB DEPTH
(inches)
MINIMUM BASE STEEL THICKNESS
mil (inches)
350S162-t 3.5 33 (0.0329), 43 (0.0428), 54 (0.0538)
550S162-t 5.5 33 (0.0329), 43 (0.0428), 54 (0.0538), 68 (0.0677)
800S162-t 8 33 (0.0329), 43 (0.0428), 54 (0.0538), 68 (0.0677)
1000S162-t 10 43 (0.0428), 54 (0.0538), 68 (0.0677)
1200S162-t 12 43 (0.0428), 54 (0.0538), 68 (0.0677)
For SI: 1 inch = 25.4 mm
  1. The member designation is defined by the first number representing the member depth in hundredths of an inch, the letter "s" representing a stud or joist member, the second number representing the flange width in hundredths of an inch and the letter "t" shall be a number representing the minimum base metal thickness in mils.
Load-bearing, cold-formed steel framing members shall have a legible label, stencil, stamp or embossment with the following information as a minimum:
  1. Manufacturer's identification.
  2. Minimum base steel thickness in inches (mm).
  3. Minimum coating designation.
  4. Minimum yield strength, in kips per square inch (ksi) (MPa).
Screws for steel-to-steel connections shall be installed with a minimum edge distance and center-to-center spacing of ½ inch (12.7 mm), shall be self-drilling tapping and shall conform to ASTM Cl513. Structural sheathing shall be attached to cold-formed steel roof rafters with minimum No. 8 self-drilling tapping screws that conform to ASTM Cl513. Screws for attaching structural sheathing to cold-formed steel roof framing shall have a minimum head diameter of 0.292 inch (7.4 mm) with countersunk heads and shall be installed with a minimum edge distance of ⅜ inch (9.5 mm). Gypsum board ceilings shall be attached to cold-formed steel joists with minimum No. 6 screws conforming to ASTM C954 or ASTM C1513 with a bugle-head style and shall be installed in accordance with Section R805. For all connections, screws shall extend through the steel a minimum of three exposed threads. Fasteners shall have rust-inhibitive coating suitable for the installation in which they are being used, or be manufactured from material not susceptible to corrosion.
Web holes, web hole reinforcing and web hole patching shall be in accordance with this section.
Web holes in roof framing members shall comply with all of the following conditions:
  1. Holes shall conform to Figure R804.2.6.1.
  2. Holes shall be permitted only along the centerline of the web of the framing member.
  3. Center-to-center spacing of holes shall not be less than 24 inches (610 mm).
  4. The web hole width shall be not greater than one-half the member depth, or 2½ inches (64 mm).
  5. Holes shall have a web hole length not exceeding 4½ inches (114 mm).
  6. The minimum distance between the edge of the bearing surface and the edge of the web hole shall be not less than 10 inches (254 mm).
     Framing members with web holes not conforming to Items 1 though 6 shall be reinforced in accordance with Section R804.2.6.2, patched in accordance with Section R804.2.6.3 or designed in accordance with accepted engineering practices.

For SI: 1 inch= 25.4 mm.
FIGURE R804.2.6.1
ROOF FRAMING MEMBER WEB HOLES
Reinforcement of web holes in ceiling joists not conforming to the requirements of Section R804.2.6.1 shall be permitted if the hole is located fully within the center 40 percent of the span and the depth and length of the hole do not exceed 65 percent of the flat width of the web. The reinforcing shall be a steel plate or C-shaped section with a hole that does not exceed the web hole size limitations of Section R804.2.6.1 for the member being reinforced. The steel reinforcing shall be the same thickness as the receiving member and shall extend not less than 1 inch (25 mm) beyond all edges of the hole. The steel reinforcing shall be fastened to the web of the receiving member with No. 8 screws spaced not greater than 1 inch (25 mm) center to center along the edges of the patch with minimum edge distance of ½ inch (12.7 mm).
Patching of web holes in roof framing members not conforming to the requirements in Section R804.2.6.1 shall be permitted in accordance with either of the following methods:
  1. Framing members shall be replaced or designed in accordance with accepted engineering practices where web holes exceed either of the following size limits:

    1.1.  The depth of the hole, measured across the web, exceeds 70 percent of the flat width of the web.
    1.2.  The length of the hole measured along the web, exceeds 10 inches (254 mm) or the depth of the web, whichever is greater.
  2. Web holes not exceeding the dimensional requirements in Section R804.2.6.3, Item 1, shall be patched with a solid steel plate, stud section or track section in accordance with Figure R804.2.6.3. The steel patch shall, as a minimum, be the same thickness as the receiving member and shall extend not less than 1 inch (25 mm) beyond all edges of the hole. The steel patch shall be fastened to the web of the receiving member with No. 8 screws spaced not greater than 1 inch (25 mm) center-to-center along the edges of the patch with minimum edge distance of 12 inch (12.7 mm).
For SI: 1 inch = 25.4 mm.
FIGURE R804.2.6.3
ROOF FRAMING MEMBER WEB HOLE PATCH
Cold-formed steel roof systems constructed in accordance with the provisions of this section shall consist of both ceiling joists and rafters in accordance with Figure R804.3 and fastened in accordance with Table R804.3.

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.
FIGURE R804.3
COLD-FORMED STEEL ROOF CONSTRUCTION
Cold-formed steel ceiling joists shall be in accordance with this section.
Ceiling joist size and thickness shall be determined in accordance with the limits set forth in Tables R804.3.1.1(1) and R804.3.1.1(2). When determining the size of ceiling joists, the lateral support of the top flange shall be classified as unbraced, braced at midspan or braced at third points in accordance with Section R804.3.1.4. Where sheathing material is attached to the top flange of ceiling joists or where the bracing is spaced closer than third point of the joists, the "third point" values from Tables R804.3.1.1(1) and R804.3.1.1(2) shall be used.

     Ceiling joists shall have a bearing support length of not less than 1½ inches (38 mm) and shall be connected to roof rafters (heel joint) with No. 10 screws in accordance with Figure R804.3.1.1 and Table 804.3.1.1(3).

     Where continuous joists are framed across interior bearing supports, the interior bearing supports shall be located within 24 inches (610 mm) of midspan of the ceiling joist, and the individual spans shall not exceed the applicable spans in Tables R804.3.1.1(1) and R804.3.1.1(2).

     Where the attic is to be used as an occupied space, the ceiling joists shall be designed in accordance with Section R505.

For SI: 1 mil = 0.0254 mm.
FIGURE R804.3.1.1
JOIST TO RAFTER CONNECTION

TABLE R804.3.1.1(1)
CEILING JOIST SPANS 10 PSF LIVE LOAD (NO ATTIC STORAGE)a, b, c
MEMBER
DESIGNATION
ALLOWABLE SPAN (feet - inches)
Lateral Support of Top (Compression) Flange
Unbraced Midspan Bracing Third-point Bracing
Ceiling Joist Spacing (inches)
16 24
16 24 16 24
350S162-33 9'-5" 8'-6" 12'-2" 10'-4" 12'-2" 10'-7"
350S162-43 10'-3" 9'-12" 13'-2" 11'-6" 13'-2" 11'-6"
350S162-54 11'-1" 9'-11" 13'-9" 12'-0" 13'-9"
12'-0"
350S162-68 12'-1" 10'-9" 14'-8" 12'-10" 14'-8" 12'-10"
550S162-33 10'-7" 9'-6" 14'-10" 12'-10" 15'-11"
13'-4"
550S162-43 11'-8" 16'-4" 14'-3" 14'-3" 17'-10" 15'-3"
550S162-54 12'-6" 17'-7" 15'-7" 15'-7" 19'-5" 16'-10"
550S162-68 13'-6" 19'-2" 17'-0" 17'-0" 21'-0" 18'-4"
800S162-33 - - - - - -
800S162-43 13'-0" 11'-9" 18'-10" 17'-0" 21'-6" 19'-0"
800S162-54 13'-10" 12'-5" 20'-0" 18'-0" 22'-9" 20'-4"
800S162-68 14'-11" 13'-4" 21'-3" 19'-1" 24'-1" 21'-8"
1000S162-43 - - - - - -
1000S162-54 14'-9" 13'-3" 21'-4" 19'-3" 24'-4" 22'-0"
1000S162-68 15'-10" 14'-2" 22'-8" 20'-5" 25'-9" 23'-2"
1200S162-43 - - - - - -
1200S162-54 - - - - - -
1200S162-68 16'-8" 14'-11" 23'-11" 21'-6" 27'-2" 24'-6"
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot= 0.0479 kPa.
  1. Deflection criterion: L/240 for total loads.
  2. Ceiling dead load = 5 psf.
  3. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.


TABLE R804.3.1.1(2)
CEILING JOIST SPANS 20 PSF LIVE LOAD (LIMITED ATTIC STORAGE)a, b, c
MEMBER
DESIGNATION
ALLOWABLE SPAN (feet - inches)
Lateral Support of Top (Compression) Flange
Unbraced Midspan Bracing Third-point Bracing
Ceiling Joist Spacing (inches)
16 24
16 24 16 24
350S162-33 8'-2" 6'-10" 9'-9" 6'-10" 9'-11" 6'-10"
350S162-43 8'-10" 7'-10" 11'-0" 9'-5" 11'-0" 9'-7"
350S162-54 9'-6" 8'-6" 11'-9" 10'-3" 11'-9" 10'-3"
350S162-68 10'-4" 9'-2" 12'-7" 11'-0" 12'-7" 11'-0"
550S162-33 9'-2" 8'-3" 12'-2" 8'-5" 12'-6" 8'-5"
550S162-43 10'-1" 9'-1" 13'-7" 11'-8" 14'-5" 12'-2"
550S162-54 10'-9" 9'-8" 14'-10" 12'-10" 15'-11" 13'-6"
550S162-68 11'-7" 10'-4" 16'-4" 14'-0" 17'-5" 14'-11"
800S162-33 - - - - - -
800S162-43 11'-4" 10'-1" 16'-5" 13'-6" 18'-1" 13'-6"
800S162-54 20'-0" 10'-9" 17'-4" 15'-6" 19'-6" 27'-0"
800Sl62-68 12'-10" 11'-6" 18'-5" 16'-6" 20'-10" 18'-3"
1000S162-43 - - - - - -
1000S162-54 12'-10" 11'-6" 18'-7" 16'-9" 21'-2" 15'-5"
10001S62-68 13'-8" 12'-3" 19'-8" 17'-8" 22'-4" 20'-1"
1200S162-43 - - - - - -
1200S162-54 - - -- - - -
1200S162-68 14'-4" 12'-11" 20'-9" 18'-8" 23'-7" 21'-3"
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot= 0.0479 kPa.
  1. Deflection criterion: L/240 for total loads.
  2. Ceiling dead load = 5 psf.
  3. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
The bottom flanges of ceiling joists shall be laterally braced by the application of gypsum board or continuous steel straps installed perpendicular to the joist run in accordance with one of the following:
  1. Gypsum board shall be fastened with No. 6 screws in accordance with Section R702.
  2. Steel straps with a minimum size of 1½ inches by 33 mils (38 mm by 0.84 mm) shall be installed at a maximum spacing of 4 feet (1219 mm). Straps shall be fastened to the bottom flange at each joist with one No. 8 screw and shall be fastened to blocking with two No. 8 screws. Blocking shall be installed between joists at a maximum spacing of 12 feet (3658 mm) measured along a line of continuous strapping (perpendicular to the joist run). Blocking shall also be located at the termination of all straps.
The top flanges of ceiling joists shall be laterally braced as required by Tables R804.3.1.1(1) and R804.3.1.1(2), in accordance with one of the following:
  1. Minimum 33-mil (0.84 mm) C-shaped member in accordance with Figure R804.3.1.3(1).
  2. Minimum 33-mil (0.84 mm) track section in accordance with Figure R804.3.1.3(1).
  3. Minimum 33-mil (0.84 mm) hat section in accordance with Figure R804.3.1.3(1).
  4. Minimum 54-mil (1.37 mm) 1½-inch (38 mm) cold-rolled channel section in accordance with Figure R804.3.1.3(1).
  5. Minimum 1½-inch by 33-mil (38 mm by 0.84 mm) continuous steel strap in accordance with Figure R804.3.1.3(2).
     Lateral bracing shall be installed perpendicular to the ceiling joists and shall be fastened to the top flange of each joist with one No. 8 screw. Blocking shall be installed between joists in line with bracing at a maximum spacing of 12 feet (3658 mm) measured perpendicular to the joists. Ends of lateral bracing shall be attached to blocking or anchored to a stable building component with two No. 8 screws.

FIGURE R804.3.1.3(1)
CEILING JOIST TOP FLANGE BRACING WITH C-SHAPED, TRACK OR COLD-ROLLED CHANNEL

For SI: 1 foot= 304.8 mm.
FIGURE R804.3.1.3(2)
CEILING JOIST TOP FLANGE BRACING WITH CONTINUOUS STEEL STRAP AND BLOCKING
Splices in ceiling joists shall be permitted, if ceiling joist splices are supported at interior bearing points and are constructed in accordance with Figure R804.3.1.4. The number of screws on each side of the splice shall be the same as required for the heel joint connection in Table R804.3.1.1(3).

For SI: 1 inch= 25.4 mm.
FIGURE R804.3.1.4
SPLICED CEILING JOISTS
Cold-formed steel roof rafters shall be in accordance with this section.
Roof rafter size and thickness shall be determined in accordance with the limits set forth in Table R804.3.2.1(1) based on the horizontal projection of the roof rafter span. For determination of roof rafter sizes, reduction of roof spans shall be permitted where a roof rafter support brace is installed in accordance with Section R804.3.2.2. The reduced roof rafter span shall be taken as the larger of the distances from the roof rafter support brace to the ridge or to the heel measured horizontally.

     For the purpose of determining roof rafter sizes in Table R804.3.2.1(1), ultimate design wind speeds shall be converted to equivalent ground snow loads in accordance with Table R804.3.2.1(2). Roof rafter sizes shall be based on the higher of the ground snow load or the equivalent snow load converted from the ultimate design wind speed.

TABLE R804.3.2.1(1)
ROOF RAFTER SPANSa, b, c, d
MEMBER
DESIGNATION
ALLOWABLE SPAN MEASURED HORIZONTALLY (feet - inches)
Ground snow load (psf)
20 30 50
70
Rafter spacing (inches)
16 24 16 24 16 24 16 24
550S162-33 14'-0" 11'-6" 11'-11" 9'-7" 9'-6" 7'-9" 8'-2" 6'-8"
550S162-43 16'-8" 13'-11" 14'-5" 11'-9" 11'-6" 9'-5" 9'-10" 8'-0"
550S162-54 17'-11" 15'-7" 15'-7" 13'-8" 13'-2" 11'-6" 11'-9" 10'-3"
550S162-68 19'-2" 16'-9" 16'-9" 14'-7" 14'-l" 12'-4" 12'-7" 11'-0"
800S162-33 16'-5" 13'-5" 13'-ll" 11'-4" 11'-1" 8'-2" 9'-0" 6'-0"
800S162-43 19'-9" 16'-1" 16'-8" 13'-7" 13'-4" 10'-10" 11'-5" 9'-4"
800S162-54 24'-2" 21'-2" 21'-1" 18'-5" 17'-10" 14'-8" 15'-5" 12'-7"
800S162-68 25'-11" 22'-8" 22'-8" 19'-9" 19'-1" 16'-8" 17'-1" 14'-9"
1000S162-43 22'-3" 18'-2" 18'-9" 15'-8" 15'-0" 12'-3" 12'-10" 10'-6"
1000S162-54 29'-0" 24'-6" 25'-4" 20'-9" 20'-3" 16'-7" 17'-5" 14'-2"
1000S162-68 31'-2" 27'-3" 27'-3" 23'-9" 20'-0" 19'-6" 20'-6" 16'-8"
1200S162-54 33'-2" 27'-1" 28'-1" 22'-11" 22'-5" 18'-4" 19'-3" 15'-8"
1200S162-68 36'-4" 31'-9" 31'-9" 27'-0" 26'-5" 21'-6" 22'-6" 18'-6"
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. Table provides maximum horizontal rafter spans in feet and inches for slopes between 3:12 and 12:12.
  2. Deflection criteria: L/240 for live loads and L/180 for total loads.
  3. Roof dead load = 12 psf.
  4. Grade 33 ksi steel is permitted to be used for 33 mil and 43 mil thicknesses. Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.


TABLE R804.3.2.1(2)
ULTIMATE DESIGN WIND SPEED TO EQUIVALENT SNOW LOAD CONVERSION
BASIC WIND SPEED
AND EXPOSURE
EQUIVALENT GROUND SNOW LOAD (psf)
Roof slope
Exp. B Exp. C 3:12 4:12 5:12 6:12 7:12 8:12 9:12 10:12 11:12 12:12
85mph - 20 20 20 20 20 20 30 30 30 30
100mph 85mph 20 20 20 20 30 30 30 30 50 50
110mph 100mph 20 20 20 20 30 50 50 50 50 50
- 110mph 30 30 30 50 50 50 70 70 70 -
For SI: 1 mile per hour= 0.447 m/s, 1 pound per square foot= 0.0479 kPa.
Eave overhangs shall not exceed 24 inches (610 mm) measured horizontally.
Rake overhangs shall not exceed 12 inches (305 mm) measured horizontally. Outlookers at gable endwalls shall be installed in accordance with Figure R804.3.2.1.2.

For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm.
FIGURE R804.3.2.1.2
GABLE ENDWALL OVERHANG DETAILS
When used to reduce roof rafter spans in determining roof rafter sizes, a roof rafter support brace shall meet all of the following conditions:
  1. Minimum 350S162-33 C-shaped brace member with maximum length of 8 feet (2438 mm).
  2. Minimum brace member slope of 45 degrees (0.785 rad) to the horizontal.
  3. Minimum connection of brace to a roof rafter and ceiling joist with four No.10 screws at each end.
  4. Maximum 6 inches (152 mm) between brace/ceiling joist connection and load-bearing wall below.
  5. Each roof rafter support brace greater than 4 feet (1219 mm) in length, shall be braced with a supplemental brace having a minimum size of 350S162-33 or 350T162-33 such that the maximum unsupported length of the roof rafter support brace is 4 feet (1219 mm). The supplemental brace shall be continuous and shall be connected to each roof rafter support brace using two No. 8 screws.
Roof rafters shall not be spliced.
Roof rafters shall be connected to a parallel ceiling joist to form a continuous tie between exterior walls in accordance with Figure R804.3.1.1 and Table R804.3.1.1(3). Ceiling joists shall be connected to the top track of the load-bearing wall in accordance with Table R804.3, either with the required number of No. 10 screws applied through the flange of the ceiling joist or by using a 54-mil (1.37 mm) clip angle with the required number of No. 10 screws in each leg. Roof rafters shall be connected to a ridge member with a minimum 2-inch by 2-inch (51 mm by 51 mm) clip angle fastened with No. 10 screws to the ridge member in accordance with Figure R804.3.2.4 and Table R804.3.2.4. The clip angle shall have a steel thickness equivalent to or greater than the roof rafter thickness and shall extend the depth of the roof rafter member to the extent possible. The ridge member shall be fabricated from a C-shaped member and a track section that shall have a minimum size and steel thickness equivalent to or greater than that of adjacent roof rafters and shall be installed in accordance with Figure R804.3.2.4. The ridge member shall extend the full depth of the sloped roof rafter cut.

For SI: 1 inch= 25.4 mm.
FIGURE R804.3.2.4
RIDGE MEMBER CONNECTION


TABLE R804.3.2.4
SCREWS REQUIRED AT EACH LEG OF CLIP ANGLE FOR ROOF RAFTER TO RIDGE MEMBER CONNECTIONa
BUILDING WIDTH (feet) NUMBER OF SCREWS
Ground snow load (psf)
0 to 20 21 to 30 31 to 50 51 to 70
24 2 2 3 4
28 2 3 4 5
32 2 3 4 5
36 3 3 5 6
40 3 4 5 7
For SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.
  1. Screws shall be No. 10 minimum.
The bottom flanges of roof rafters shall be continuously braced, at a maximum spacing of 8 feet (2440 mm) as measured parallel to the roof rafters, with one of the following members:
  1. Minimum 33-mil (0.84 mm) C-shaped member.
  2. Minimum 33-rnil (0.84 mm) track section.
  3. Minimum 1½-inch by 33-mil (38 mm by 0.84 mm) steel strap.
     The bracing element shall be fastened to the bottom flange of each roof rafter with one No. 8 screw and shall be fastened to blocking with two No. 8 screws. Blocking shall be installed between roof rafters in-line with the continuous bracing at a maximum spacing of 12 feet (3658 mm) measured perpendicular to the roof rafters. The ends of continuous bracing shall be fastened to blocking or anchored to a stable building component with two No. 8 screws.
Flanges and lips of load-bearing, cold-formed steel roof framing members shall not be cut or notched.
Roof-ceiling framing above wall openings shall be supported on headers. The allowable spans for headers in load-bearing walls shall not exceed the values set forth in Section R603.6 and Tables R603.6(1) through R603.6(6).
Openings in roofs and ceilings shall be framed with header and trimmer joists. Header joist spans shall not exceed 4 feet (1219 mm) in length. Header and trimmer joists shall be fabricated from joist and track members having a minimum size and thickness equivalent to the adjacent ceiling joists or roof rafters and shall be installed in accordance with Figures R804.3.5(1) and R804.3.5(2). Each header joist shall be connected to trimmer joists with not less than four 2-inch by 2-inch (51 by 51 mm) clip angles. Each clip angle shall be fastened to both the header and trimmer joists with four No. 8 screws, evenly spaced, through each leg of the clip angle. The steel thickness of the clip angles shall be not less than that of the ceiling joist or roof rafter. Each track section for a built-up header or trimmer joist shall extend the full length of the joist (continuous).
For SI: 1 foot= 304.8 mm.
FIGURE R804.3.5(1)
ROOF OR CEILING OPENING

For SI: 1 inch= 25.4 mm.
FIGURE R804.3.5(2)
HEADER TO TRIMMER CONNECTION
Cold-formed steel trusses shall be designed and installed in accordance with AISI S100, Section D4. In the absence of specific bracing requirements, trusses shall be braced in accordance with accepted industry practices, such as the SBCA Cold-Formed Steel Building Component Safety Information (CFSBCSI) Guide to Good Practice for Handling, Installing & Bracing of Cold-Formed Steel Trusses. Trusses shall be connected to the top track of the load-bearing wall in accordance with Table R804.3, either with two No. 10 screws applied through the flange of the truss or by using a 54-mil (1.37 mm) clip angle with two No. 10 screws in each leg.
Ceiling and roof diaphragms shall be in accordance with this section.
At gable endwalls a ceiling diaphragm shall be provided by attaching a minimum ½-inch (12.7 mm) gypsum board or a minimum ⅜-inch (9.5 mm) wood structural panel sheathing, that complies with Section R803, to the bottom of ceiling joists or roof trusses and connected to wall framing in accordance with Figures R804.3.7.1(1) and R804.3.7.1(2), unless studs are designed as full height without bracing at the ceiling. Flat blocking shall consist of C-shaped or track section with a minimum thickness of 33 mils (0.84 mm). For a gypsum board sheathed ceiling, the diaphragm length shall be in accordance with Table R804.3.7.1. For a wood structural panel sheathed ceiling, the diaphragm length shall be not less than 12 feet (3658 mm) for building widths less than 36 feet (10973 mm), or not less than 14 feet (4267 mm) for building widths greater than or equal to 36 feet (10973 mm).

     The ceiling diaphragm shall be secured with screws spaced at a maximum 6 inches (152 mm) o.c. at panel edges and a maximum 12 inches (305 mm) o.c. in the field. The required lengths in Table R804.3.7.1 for gypsum board sheathed ceiling diaphragms shall be permitted to be multiplied by 0.35 if all panel edges are blocked. Multiplying the required lengths in Table R804.3.7.1 for gypsum board sheathed ceiling diaphragms by 0.9 shall be permitted if all panel edges are secured with screws spaced at 4 inches (102 mm) o.c.

For SI: 1 inch= 25.4 mm.
FIGURE R804.3.7.1(1)
CEILING DIAPHRAGM TO GABLE ENDWALL DETAIL

For SI: 1 inch= 25.4 mm.
FIGURE RB04.3.7.1(2)
CEILING DIAPHRAGM TO SIDEWALL DETAIL
TABLE R804.3.7.1
REQUIRED LENGTHS FOR CEILING DIAPHRAGMS AT GABLE ENDWALLS GYPSUM BOARD SHEATHED, CEILING HEIGHT = 8 FEETa, b, c, d, e, f, g
EXPOSURE CATEGORY ULTIMATE DESIGN WIND SPEED (mph)
B 126 < 139
- -
C
110 - 126 < 139
Roof pitch Building endwall width (feet) Minimum diaphragm length (feet)
3:12
to
6:12
24 - 28 20 22 28 32
> 28 - 32 22 28 32 38
> 32 - 36 26 32 38 44
> 36 - 40 30 36 44 50
6:12
to
9:12
> 24 - 28 22 26 32 36
> 28 - 32 26 32 38 44
> 32 - 36 32 38 44 52
> 36 - 40 36 44 52 60
9:12
to
12:12
> 24 - 28 26 30 36 42
> 28 - 32 30 36 42 50
> 32 - 36 36 42 50 60
> 36 - 40 42 50 60 70
For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa, 1 mile per hour = 0.447 m/s, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.
  1. Ceiling diaphragm is composed of ½-inch gypsum board (min. thickness) secured with screws spaced at 6 inches o.c. at panel edges and 12 inches o.c. infield. Use No. 8 screws (min.) where framing members have a designation thickness of 54 mils or less and No. 10 screws (min.) where framing members have a designation thickness greater than 54 mils.
  2. Maximum aspect ratio (length/width) of diaphragms is 2:1.
  3. Building width is in the direction of horizontal framing members supported by the wall studs.
  4. Required diaphragm lengths are to be provided at each end of the structure.
  5. Multiplying required diaphragm lengths by 0.35 is permitted if all panel edges are blocked.
  6. Multiplying required diaphragm lengths by 0.9 is permitted if all panel edges are secured with screws spaced at 4 inches o.c.
  7. To determjne the minimum diaphragm length for buildings with ceiling heights of 9 feet or 10 feet values in the table above shall be multiplied by 1.15.
A roof diaphragm shall be provided by attaching a minimum of ⅜-inch (9.5 mm) wood structural panel which complies with Section R803 to roof rafters or truss top chords in accordance with Table R804.3. Buildings with 3:1 or larger plan aspect ratio and with roof rafter slope (pitch) of 9:12 or larger shall have the roof rafters and ceiling joists blocked in accordance with Figure R804.3.7(2).
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm.
FIGURE R804.3.7(2)
ROOF BLOCKING DETAIL
Roof assemblies shall be connected to walls below in accordance with Table R804.3. A continuous load path shall be provided to transfer uplift loads to the foundation.
Ceilings shall be installed in accordance with the requirements for interior wall finishes as provided in Section R702.
Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilation openings shall have a least dimension of 116 inch (1.6 mm) minimum and ¼ inch (6.4 mm) maximum. Ventilation openings having a least dimension larger than ¼ inch (6.4 mm) shall be provided with corrosion-resistant wire cloth screening, hardware cloth or similar material with openings having a least dimension of 116 inch (1.6 mm) minimum and ¼ inch (6.4 mm) maximum. Openings in roof framing members shall conform to the requirements of Section R802.7. Required ventilation openings shall open directly to the outside air.
The minimum net free ventilating area shall be 1150 of the area of the vented space.
    
    Exception: The minimum net free ventilation area shall be 1300 of the vented space provided one or more of the following conditions are met:
  1. In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.
  2. Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically, with the balance of the required ventilation provided by eave or cornice vents. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet (914 mm) below the ridge or highest point of the space shall be permitted.
Where eave or cornice vents are installed, insulation shall not block the free flow of air. Not less than a 1-inch (25 mm) space shall be provided between the insulation and the roof sheathing and at the location of the vent.
Ventilators shall be installed in accordance with manufacturer's instructions. Installation of ventilators in roof systems shall be in accordance with the requirements of Section R903. Installation of ventilators in wall systems shall be in accordance with the requirements of Section R703.1.
Unvented attics and unvented enclosed roof framing assemblies created by ceilings that are applied directly to the underside of the roof framing members and structural roof sheathing applied directly to the top of the roof framing members/rafters, shall be permitted where all the following conditions are met:
  1. The unvented attic space is completely within the building thermal envelope.
  2. No interior Class I vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed roof framing assembly.
  3. Where wood shingles or shakes are used, a minimum ¼-inch (6.4 mm) vented airspace separates the shingles or shakes and the roofing underlayment above the structural sheathing.
  4. In Climate Zones 5, 6, 7 and 8, any air-impermeable insulation shall be a Class II vapor retarder, or shall have a Class II vapor retarder coating or covering in direct contact with the underside of the insulation.
  5. Insulation shall be located in accordance with the following:
    1. Item 5.1.1, 5.1.2, 5.1.3 or 5.1.4 shall be met, depending on the air permeability of the insulation directly under the structural roof sheathing.
      1. Where only air-impermeable insulation is provided, it shall be applied in direct contact with the underside of the structural roof sheathing.
      2. Where air-permeable insulation is provided inside the building thermal envelope, it shall be installed in accordance with Section 5.1. In addition to the air-permeable insulation installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing in accordance with the R-values in Table R806.5 for condensation control.
      3. Where both air-impermeable and air-permeable insulation are provided, the air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing in accordance with Item 5.1.1 and shall be in accordance with the R-values in Table R806.5 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.
      4. Alternatively, sufficient rigid board or sheet insulation shall be installed directly above the structural roof sheathing to maintain the monthly average temperature of the underside of the structural roof sheathing above 45°F (7°C). For calculation purposes, an interior air temperature of 68°F (20°C) is assumed and the exterior air temperature is assumed to be the monthly average outside air temperature of the three coldest months.
    2. Where preformed insulation board is used as the air-impermeable insulation layer, it shall be sealed at the perimeter of each individual sheet interior surface to form a continuous layer.

TABLE R806.5
INSULATION FOR CONDENSATION CONTROL
CLIMATE ZONE MINIMUM RIGID BOARD ON AIR-
IMPERMEABLE INSULATION R-VALUEa, b
2B and 3B tile roof only 0 (none required)
1, 2A, 2B, 3A, 3B, 3C R-5
4C R-10
4A, 4B R-15
5 R-20
6 R-25
7 R-30
8 R-35
  1. Contributes to but does not supersede the requirements in Section N1102.
  2. Alternatively, sufficient continuous insulation shall be installed directly above the structural roof sheathing to maintain the monthly average temperature of the underside of the structural roof sheathing above 45°F (7°C). For calculation purposes, an interior air temperature of 68°F (20°C) is assumed and the exterior air temperature is assumed to be the monthly average outside air temperature of the three coldest months.
Buildings with combustible ceiling or roof construction shall have an attic access opening to attic areas that have a vertical height of 30 inches (762 mm) or greater over an area of not less than 30 square feet (2.8 m2). The vertical height shall be measured from the top of the ceiling framing members to the underside of the roof framing members.

     The rough-framed opening shall be not less than 22 inches by 30 inches (559 mm by 762 mm) and shall be located in a hallway or other readily accessible location. Where located in a wall, the opening shall be not less than 22 inches wide by 30 inches high (559 mm wide by 762 mm high). Where the access is located in a ceiling, minimum unobstructed headroom in the attic space shall be 30 inches (762 mm) at some point above the access measured vertically from the bottom of ceiling framing members. See Section M1305.1.3 for access requirements where mechanical equipment is located in attics.
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