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About this chapter: Chapter 8 addresses the design and construction of roof-ceiling systems. This chapter contains two roof-ceiling framing systems: wood framing and cold-formed steel framing. Allowable span tables are provided to simplify the selection of rafter and ceiling joist size for wood roof framing and cold-formed steel framing. Chapter 8 also provides requirements for the application of ceiling finishes, the proper ventilation of concealed spaces in roofs (for example, enclosed attics and rafter spaces), unvented attic assemblies and attic access.
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 soils 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 R802.1.1 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 A190.1, ANSI 117 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-retardant-treated 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. In addition, the ASTM E84 or UL 723 test shall be continued for an additional 20-minute period and 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 impregnated with chemicals 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. The use of paints, coating, stains or other surface treatments is not an approved method of protection as required by this section.
For fire-retardant-treated wood products, the front and back faces of the wood product shall be tested in accordance with and produce the results required in Section R802.1.5.
Wood structural panels shall be tested with a ripped or cut longitudinal gap of 1/8 inch (3.2 mm).
In addition to the labels required by Section 802.1.1 for sawn lumber and Section 803.2.1 for wood structural panels, each piece of fire-retardant-treated lumber and wood structural panel 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-retardant-treated wood. Adjustments to design values shall be based on an approved method of investigation that takes into consideration the effects of the anticipated temperature and humidity to which the fire-retardant-treated 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.
Structural capacities and design provisions for prefabricated wood I-joists shall be established and monitored in accordance with ASTM D5055.
The roof and ceiling assembly shall provide continuous ties across the structure to prevent roof thrust from being applied to the supporting walls. The assembly 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.
A ridge board used to connect opposing rafters shall be not less than 1 inch (25 mm) nominal thickness and not less in depth than the cut end of the rafter. Where ceiling joist or rafter ties do not provide continuous ties across the structure as required by Section R802.5.2, the ridge shall be supported by a wall or ridge beam designed in accordance with accepted engineering practice and supported on each end by a wall or column.
Upcodes Diagrams
Rafters shall be in accordance with this section.
Rafters shall be sized based on the rafter spans in Tables R802.4.1(1) through R802.4.1(8). Rafter spans shall be measured along the horizontal projection of the rafter. For other grades and species and for other loading conditions, refer to the AWC STJR.
TABLE R802.4.1(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 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 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 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 adjustment factors in Table R802.4.1(9).
  2. Span exceeds 26 feet in length.
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 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 19-11
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 adjustment factors in Table R802.4.1(9).
  2. Span exceeds 26 feet in length.
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 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 adjustment factors in Table R802.4.1(9).
  2. Span exceeds 26 feet in length.
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 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 5-11 8-9 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 adjustment factors in Table R802.4.1(9).
  2. Span exceeds 26 feet in length.
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 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 11-8 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 adjustment factors in Table R802.4.1(9).
  2. Span exceeds 26 feet in length.
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 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 adjustment factors in Table R802.4.1(9).
RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 70 psf, ceiling not attached to rafters, L/Δ = 180)
RAFTER SPACING (inches) SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 8-1 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 adjustment factors in Table R802.4.1(9).
RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 70 psf, ceiling attached to rafters, L/Δ = 240)
RAFTER SPACING (inches) SPECIES AND GRADE DEAD LOAD = 10 psf DEAD LOAD = 20 psf
2 × 4 2 × 6 2 × 8 2 × 10 2 × 12 2 × 4 2 × 6 2 × 8 2 × 10 2 × 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 adjustment factors in Table R802.4.1(9).
RAFTER SPAN ADJUSTMENT FACTOR
HC/HRa RAFTER SPAN ADJUSTMENT FACTOR
1/3 0.67
1/4 0.76
1/5 0.83
1/6 0.90
1/7.5 or less 1.00
  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.
Rafters shall be framed opposite from each other to a ridge board, shall not be offset more than 11/2 inches (38 mm) from each other and shall be connected with a collar tie or ridge strap in accordance with Section R802.4.6 or directly opposite from each other to a gusset plate in accordance with Table R602.3(1). Rafters shall be nailed to the top wall plates in accordance with Table R602.3(1) unless the roof assembly is required to comply with the uplift requirements of Section R802.11.
Hip and valley rafters shall be not less than 2 inches (51 mm) nominal in 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 3:12 (25-percent slope), structural members that support rafters, such as ridges, hips and valleys, shall be designed as beams, and bearing shall be provided for rafters in accordance with Section R802.6.
Installation of purlins to reduce the span of rafters is permitted as shown in Figure R802.4.5. 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 degree = 0.018 rad.
HC = Height of ceiling joists or rafter ties measured vertically above the top of rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
FIGURE R802.4.5
BRACED RAFTER CONSTRUCTION
Where collar ties are used to connect opposing rafters, they shall be located in the upper third of the attic space and fastened in accordance with Table R602.3(1). Collar ties shall be not less than 1 inch by 4 inches (25 mm × 102 mm) nominal, spaced not more than 4 feet (1219 mm) on center. Ridge straps shall be permitted to replace collar ties. Ridge straps shall be not less than 11/4-inch (32 mm) × 20 gage and shall be nailed to the top edge of each rafter with not fewer than three 10d common (3" × 0.148") nails with the closest nail not closer than 23/8 inches (60.3 mm)from the end of the rafter.
Ceiling joists shall be continuous across the structure or securely joined where they meet over interior partitions in accordance with Section R802.5.2.1. Ceiling joists shall be fastened to the top plate in accordance with Table R602.3(1).
Upcodes Diagrams
Ceiling joists shall be sized based on the joist spans in Tables R802.5.1(1) and R802.5.1(2). For other grades and species and for other loading conditions, refer to the AWC STJR.
TABLE R802.5.1(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 × 4 2 × 6 2 × 8 2 × 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 12-5 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.
  1. Span exceeds 26 feet in length.
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 = 10 psf
2 × 4 2 × 6 2 × 8 2 × 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.
  1. Span exceeds 26 feet in length.
Upcodes Diagrams
Where ceiling joists run parallel to rafters and are located in the bottom third of the rafter height, they shall be installed in accordance with Figure R802.4.5 and fastened to rafters in accordance with Table R802.5.2(1). Where the ceiling joists are installed above the bottom third of the rafter height, the ridge shall be designed as a beam in accordance with Section R802.3. Where ceiling joists do not run parallel to rafters, rafters shall be tied across the structure with a rafter tie in accordance with Section R802.5.2.2, or the ridge shall be designed as a beam in accordance with Section R802.3.
TABLE R802.5.2(1)
RAFTER/CEILING JOIST HEEL JOINT CONNECTIONSg
RAFTER SLOPE RAFTER SPACING (inches) GROUND SNOW LOAD (psf)
20e 30 50 70
Roof span (feet)
12 24 36 12 24 36 12 24 36 12 24 36
Required number of 16d common nails per heel joint splices a, b,c, d, f
3:12 12 3 5 8 3 6 9 5 9 13 6 12 17
16 4 7 10 4 8 12 6 12 17 8 15 23
19.2 4 8 12 5 10 14 7 14 21 9 18 27
24 5 10 15 6 12 18 9 17 26 12 23 34
4:12 12 3 4 6 3 5 7 4 7 10 5 9 13
16 3 5 8 3 6 9 5 9 13 6 12 17
19.2 3 6 9 4 7 11 6 11 16 7 14 21
24 4 8 11 5 9 13 7 13 19 9 17 26
5:12 12 3 3 5 3 4 6 3 6 8 4 7 11
16 3 4 6 3 5 7 4 7 11 5 9 14
19.2 3 5 7 3 6 9 5 9 13 6 11 17
24 3 6 9 4 7 11 6 11 16 7 14 21
7:12 12 3 3 4 3 3 4 3 4 6 3 5 8
16 3 3 5 3 4 5 3 5 8 4 7 10
19.2 3 4 5 3 4 6 3 6 9 4 8 12
24 3 5 7 3 5 8 4 8 11 5 10 15
9:12 12 3 3 3 3 3 3 3 3 5 3 4 6
16 3 3 4 3 3 4 3 4 6 3 5 8
19.2 3 3 4 3 4 5 3 5 7 3 6 9
24 3 4 5 3 4 6 3 6 9 4 8 12
12:12 12 3 3 3 3 3 3 3 3 4 3 3 5
16 3 3 3 3 3 3 3 3 5 3 4 6
19.2 3 3 3 3 3 4 3 4 6 3 5 7
24 3 3 4 3 3 5 3 5 7 3 6 9
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
  1. 10d common (3" × 0.148") nails shall be permitted to be substituted for 16d common (31/2" × 0.162") nails where the required number of nails is taken as 1.2 times the required number of 16d common nails, rounded up to the next full nail.
  2. Heel joint connections are not required where the ridge is supported by a load-bearing wall, header or ridge beam.
  3. 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.
  4. Equivalent nailing patterns are required for ceiling joist to ceiling joist lap splices.
  5. Applies to roof live load of 20 psf or less.
  6. 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 adjustment factors in Table 802.5.2(2).
  7. Tabulated requirements are based on 10 psf roof dead load in combination with the specified roof snow load and roof live load.
HEEL JOINT CONNECTION ADJUSTMENT FACTORS
HC/HRa, b HEEL JOINT CONNECTION ADJUSTMENT FACTOR
1/3 1.5
1/4 1.33
1/5 1.25
1/6 1.2
1/10 or less 1.11
  1. HC = Height of ceiling joists or rafter ties measured vertically from the top of the rafter support walls to the bottom of the ceiling joists or rafter ties; HR = Height of roof ridge measured vertically from the top of the rafter support walls to the bottom of the roof ridge.
  2. Where HC/HR exceeds 1/3, connections shall be designed in accordance with accepted engineering practice.
Upcodes Diagrams
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 the continuous tie across the building, lapped joists shall be nailed together in accordance with Table R802.5.2(1) and butted joists shall be tied together with a connection of equivalent capacity. Laps in joists that do not provide the continuous tie across the building shall be permitted to be nailed in accordance with Table R602.3(1).
Wood rafter ties shall be not less than 2 inches by 4 inches (51 mm × 102 mm) installed in accordance with Table R802.5.2(1) at a maximum of 24 inches (610 mm) on center. Other approved rafter tie methods shall be permitted.
Blocking shall be not less than utility grade lumber.
The ends of each rafter or ceiling joist shall have not less than 11/2 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 (30 968 mm2). Where the roof pitch is greater than or equal to 3 units vertical in 12 units horizontal (25-percent slope), and ceiling joists or rafter ties are connected to rafters to provide a continuous tension tie in accordance with Section R802.5.2, vertical bearing of the top of the rafter against the ridge board shall satisfy this bearing requirement.
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 31/2 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 to Section R802.10.1, shall be provided to the building official and approved prior to installation. Truss design drawings shall be provided with the shipment of trusses delivered to the job site. Truss design drawings shall include, at a minimum, the following information:
  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 (as determined from Section R301.6).
    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 such as size, thickness or gage 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:
    1. Truss to girder-truss.
    2. Truss ply to ply.
    3. Field splices.
  10. Calculated deflection ratio 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.
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 design 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 where snow controls for buildings that are not greater than 60 feet (18 288 mm) in length perpendicular to the joist, rafter or truss span, not greater than 36 feet (10 973 mm) in width parallel to the joist, rafter or truss span, not more than three stories above grade plane in height, and have 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 provisions 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 and R802.11.2.

Exceptions: Rafters or trusses shall be permitted to be attached to their supporting wall assemblies in accordance with Table R602.3(1) where either of the following occur:
  1. Where the uplift force per rafter or truss does not exceed 200 pounds (90.8 kg) as determined by Table R802.11.
  2. Where the basic wind speed does not exceed 115 miles per hour (51.4 m/s), the wind exposure category is B, the roof pitch is 5 units vertical in 12 units horizontal (42-percent slope) or greater, the roof span is 32 feet (9754 mm) or less, and rafters and trusses are spaced not more than 24 inches (610 mm) on center.
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
EXPOSURE C
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 1,120 1,048
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 pound per linear foot = 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 R301.2.1(2) 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 pounds per linear foot 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.
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(2) and listed in Table R301.2 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.
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 5/8
48a 11/2 T & G
60b
72c
For SI: 1 inch = 25.4 mm.
  1. Minimum 270Fb, 340,000E.
  2. Minimum 420Fb, 660,000E.
  3. Minimum 600Fb, 1,150,000E.
Wood structural panels shall conform to DOC PS 1, DOC PS 2, CSA O325 or CSA O437, 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. Wood structural panel roof sheathing in accordance with Table R503.2.1.1(1) shall not cantilever more than 9 inches (229 mm) beyond the gable endwall unless supported by gable overhang framing.
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 (18 288 mm) perpendicular to the joist, rafter or truss span, not greater than 40 feet (12 192 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 140 miles per hour (63 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 and ceiling framing for buildings exceeding the applicability limits of Section R804.1.1 is permitted to be designed and constructed in accordance with AISI S230, subject to the limits therein.
Cold-formed steel roof framing constructed in accordance with Section R804 shall be located in line with the tolerances specified in AISI S240, Section B1.2.3.
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 AISI S240, Section A3.
Load-bearing, cold-formed steel framing shall have a protective coating complying with AISI S240, Section A4.
Load-bearing, cold-formed steel roof framing members shall comply with AISI S230, Section A4.3 and material grade requirements as specified in AISI S230, Section A4.4.
Load-bearing, cold-formed steel framing members shall meet the product identification requirements of AISI S240, Section A5.5.
Screws for steel-to-steel connections shall be installed with a minimum edge distance and center-to-center spacing of 1/2 inch (12.7 mm), shall be self-drilling tapping and shall conform to ASTM C1513. Structural sheathing shall be attached to cold-formed steel roof rafters with minimum No. 8 self-drilling tapping screws that conform to ASTM C1513. 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 3/8 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 not fewer than 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 in roof or ceiling joists shall comply with the conditions as prescribed in AISI S230, Section A4.5. Web holes not in conformance to the conditions of AISI S230, Section A4.5 shall be reinforced in accordance with the provisions of AISI S230, Section A4.6 or patched in accordance with the provisions of AISI S230, Section A4.7.
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


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.
Gypsum board to ceiling joists No. 6 screws 12" o.c.
Gable end truss to endwall top track No. 10 screws 12" o.c.
Rafter to ceiling joist and to ridge member Minimum No. 10 screws, in accordance with Table R804.3.1.1(3) Evenly spaced, not less than 1/2" from all edges.
Ceiling joist or roof truss to top track of bearing wallb Ceiling joist or truss spacing (in.) Roof Span (ft) Ultimate Design Wind Speed (mph) and Exposure Category Each ceiling joist or roof truss.
130 B 115 C < 139 B
120 C
130 C < 139 C
16 24 3 3 4 5
28 3 3 4 5
32 3 4 5 6
36 4 4 5 6
40 4 4 6 7
24 24 4 5 6 7
28 4 5 6 8
32 4 6 7 8
36 4 6 8 9
40 6 6 8 10
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.
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 R804.3.1.3. Where sheathing material is attached to the top flange of ceiling joists or where the bracing is spaced closer than at third points 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 11/2 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 R804.3.1.1(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.
CEILING JOIST SPANS 10 PSF LIVE LOAD (NO ATTIC STORAGE)a, b, c, d
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'-6" 8'-6" 11'-10" 9'-10" 11'-10" 10'-4"
350S162-43
10'-4" 9'-3" 12'-10" 11'-3" 12'-10" 11'-3"
350S162-54
11'-1" 9'-11" 13'-9" 12'-0" 13'-9" 12'-0"
350S162-68
12'-2" 10'-10" 14'-9" 12'-10" 14'-9" 12'-10"
550S162-33
10'-11" 9'-10" 15'-7" 12'-0" 16'-10" 12'-0"
550S162-43
11'-8" 10'-6" 16'-10" 14'-10" 18'-4" 16'-0"
550S162-54
12'-7" 11'-3" 18'-0" 16'-2" 19'-4" 17'-2"
550S162-68
13'-7" 12'-1" 19'-3" 17'-3" 20'-6" 18'-5"
800S162-33
800S162-43
13'-1" 11'-9" 18'-9" 16'-9" 21'-2" 18'-7"
800S162-54
13'-11" 12'-6" 20'-1" 18'-1" 21'-5" 20'-5"
800S162-68
14'-11" 13'-4" 21'-4" 19'-2" 22'-9" 21'-9"
1000S162-43
1000S162-54
14'-10" 13'-4" 21'-4" 19'-2" 22'-8" 21'-8"
1000S162-68
15'-10" 14'-3" 22'-9" 20'-5" 24'-3" 23'-3"
1200S162-43
1200S162-54
1200S162-68
16'-8" 14'-11" 23'-11" 21'-7" 25'-5" 24'-5"
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.
  4. Listed allowable spans are not applicable for 350S162-33, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.
CEILING JOIST SPANS 20 PSF LIVE LOAD (LIMITED ATTIC STORAGE)a, b, c, d
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'-0" 6'-5" 9'-2" 7'-5" 9'-11" 7'-5"
350S162-43
8'-11" 7'-8" 10'-9" 8'-9" 10'-0" 9'-6"
350S162-54
9'-7" 8'-7" 11'-7" 10'-2" 11'-7" 10'-2"
350S162-68
10'-4" 9'-3" 12'-5" 10'-10" 12'-5" 10'-10"
550S162-33
9'-5" 6'-11" 10'-5" 6'-11" 10'-5" 6'-11"
550S162-43
10'-2" 9'-2" 14'-2" 11'-8" 15'-2" 11'-8"
550S162-54
10'-10" 9'-9" 15'-7" 14'-0" 16'-7" 14'-5"
550S162-68
11'-8" 10'-5" 16'-7" 14'-10" 17'-9" 15'-6"
800S162-33
800S162-43
11'-4" 10'-2" 16'-1" 11'-0" 16'-6" 11'-0"
800S162-54
12'-0" 10'-10" 17'-4" 15'-7" 18'-7" 17'-7"
800S162-68
12'-10" 11'-6" 18'-6" 16'-7" 19'-11" 18'-11"
1000S162-43
1000S162-54
12'-10" 11'-7" 18'-5" 16'-6" 19'-8" 18'-8"
1000S162-68
13'-8" 12'-3" 19'-8" 17'-9" 21'-1" 20'-1"
1200S162-43
1200S162-54
1200S162-68
14'-5" 12'-11" 20'-9" 18'-7" 22'-0" 21'-0"
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 deal 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.
  4. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.
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 foot = 304.8 mm, 1 pound per square foot = 0.0479kPa.
  1. Screws shall be No. 10.

For SI: 1 mil = 0.0254 mm.
FIGURE R804.3.1.1
JOIST TO RAFTER CONNECTION
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 11/2 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), and 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) 11/2-inch (38 mm) cold-rolled channel section in accordance with Figure R804.3.1.3(1).
  5. Minimum 11/2-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 foot = 304.8 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.
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
13'-11" 11'-4" 11'-9" 9'-7" 9'-5" 7'-8" 8'-1" 6'-7"
550S162-43
15'-9" 13'-8" 14'-3" 11'-8" 11'-4" 9'-3" 9'-9" 7'-11"
550S162-54
16'-11" 14'-10" 15'-3" 13'-4" 13'-3" 11'-7" 12'-0" 10'-6"
550S162-68
18'-2" 15'-10" 16'-5" 14'-4" 14'-3" 12'-5" 12'-11" 11'-3"
800S162-33
16'-4" 13'-4" 13'-11" 11'-4" 11'-1" 9'-0" 9'-6" 6'-7"
800S162-43
19'-7" 16'-0" 16'-8" 13'-7" 13'-4" 10'-10" 11'-5" 9'-4"
800S162-54
22'-9" 19'-11" 20'-7" 17'-11" 17'-10" 4'-9" 15'-6" 12'-7"
800S162-68
24'-7" 21'-6" 22'-2" 19'-5" 19'-3" 16'-10" 17'-5" 14'-8"
1000S162-43
22'-2" 18'-1" 18'-10" 15'-4" 15'-1" 12'-4" 12'-11" 10'-7"
1000S162-54
27'-1" 23'-8" 24'-6" 20'-9" 20'-5" 16'-8" 17'-6" 14'-3"
1000S162-68
29'-5" 25'-8" 26'-6" 23'-2" 23'-0" 19'-6" 20'-6" 16'-9"
1200S162-54
31'-3" 27'-0" 28'-1" 22'-11" 22'-6" 18'-4" 19'-4" 15'-9"
1200S162-68
34'-0" 29'-8" 30'-8" 26'-9" 26'-6" 21'-7" 22'-8" 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.
ULTIMATE DESIGN WIND SPEED TO EQUIVALENT SNOW LOAD CONVERSION
ULTIMATE
WIND SPEED AND EXPOSURE
EQUIVALENT GROUND SNOW LOAD (psf)
Roof slope
Exposure Wind speed (mph) 3:12 4:12 5:12 6:12 7:12 8:12 9:12 10:12 11:12 12:12
B 115 20 20 20 20 20 20 20 20 20 20
120 20 20 20 20 20 20 20 20 20 20
130 20 20 20 20 20 20 20 20 20 20
< 140 20 20 20 20 20 20 20 30 30 30
C 115 20 20 20 20 20 20 20 20 30 30
120 20 20 20 20 20 20 20 30 30 50
130 20 20 30 30 30 30 30 30 50 50
< 140 30 30 50 50 30 30 50 50 50 50
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 the limitations provided for Option 1 or 2 in Figure R804.3.2.1.2. Outlookers at gable endwalls shall be installed in accordance with Figure R804.3.2.1.2. The required strength for uplift connectors required for Option 1 shall be determined in accordance with AISI S230, Table F3-4.

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 1.6 kph.
FIGURE R804.3.2.1.2
GABLE ENDWALL OVERHANG DETAILS
Where 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


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 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 4 feet (1219 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-mil (0.84 mm) track section.
  3. Minimum 11/2-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 S230, Section F6. 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 the required number of No. 10 screws applied through the flange of the truss or by using a 54-mil (1.37 mm) clip angle with the required number of 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 1/2-inch (12.7 mm) gypsum board or a minimum 3/8-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 (10 973 mm), or not less than 14 feet (4267 mm) for building widths greater than or equal to 36 feet (10 973 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.

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 115 120 130 < 140
C 115 120 130 < 140
Roof pitch Building endwall width
(feet)
Minimum diaphragm length (feet)    
3:12 to 6:12
24—28 16 18 24 26 30 34
> 28—32 20 20 26 32 34 40
> 32—36 24 26 30 36 42 46
> 36—40 26 28 36 40 48 52
6:12 to 9:12
> 24—28 20 20 26 30 34 38
> 28—32 24 26 30 36 42 46
> 32—36 26 30 38 42 48 54
> 36—40 30 34 40 50 56 62
9:12 to 12:12
> 24—28 22 24 30 34 38 44
> 28—32 26 28 36 40 46 52
> 32—36 30 32 40 48 54 62
> 36—40 36 38 48 56 64 72
For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.
  1. Ceiling diaphragm is composed of 1/2-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 determine the minimum diaphragm length for buildings with ceiling heights of 9 feet or 10 feet values in this table shall be multiplied by 1.15.


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 R804.3.7.1(2)
CEILING DIAPHRAGM TO SIDEWALL DETAIL
A roof diaphragm shall be provided by attaching not less than 3/8-inch (9.5 mm) wood structural panel that 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, 1 foot = 304.8 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 Sections R702.1 through R702.6.
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 1/16 inch (1.6 mm) minimum and 1/4 inch (6.4 mm) maximum. Ventilation openings having a least dimension larger than 1/4 inch (6.4 mm) shall be provided with corrosion-resistant wire cloth screening, hardware cloth, perforated vinyl or similar material with openings having a least dimension of 1/16 inch (1.6 mm) minimum and 1/4 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 and shall be protected to prevent the entry of birds, rodents, snakes and other similar creatures.
The minimum net free ventilating area shall be 1/150 of the area of the vented space.
Exception: The minimum net free ventilation area shall be 1/300 of the vented space provided both 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. The balance of the required ventilation provided shall be located in the bottom one-third of the attic space. 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, blocking, bridging and 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. Interior Class I vapor retarders are not 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 1/4-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 comply with Item 5.3 and either Item 5.1 or 5.2:
    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 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. In Climate Zones 1, 2 and 3, air-permeable insulation installed in unvented attics shall meet the following requirements:
      1. An approved vapor diffusion port shall be installed not more than 12 inches (305 mm) from the highest point of the roof, measured vertically from the highest point of the roof to the lower edge of the port.
      2. The port area shall be greater than or equal to 1:600 of the ceiling area. Where there are multiple ports in the attic, the sum of the port areas shall be greater than or equal to the area requirement.
      3. The vapor-permeable membrane in the vapor diffusion port shall have a vapor permeance rating of greater than or equal to 20 perms when tested in accordance with Procedure A of ASTM E96.
      4. The vapor diffusion port shall serve as an air barrier between the attic and the exterior of the building.
      5. The vapor diffusion port shall protect the attic against the entrance of rain and snow.
      6. Framing members and blocking shall not block the free flow of water vapor to the port. Not less than a 2-inch (51 mm) space shall be provided between any blocking and the roof sheathing. Air-permeable insulation shall be permitted within that space.
      7. The roof slope shall be greater than or equal to 3:12 (vertical/horizontal).
      8. Where only air-permeable insulation is used, it shall be installed directly below the structural roof sheathing, on top of the attic floor, or on top of the ceiling.
      9. Air-impermeable insulation, where used in conjunction with air-permeable insulation, shall be directly above or below the structural roof sheathing and is not required to meet the R-value in Table R806.5. Where directly below the structural roof sheathing, there shall be no space between the air-impermeable insulation and air-permeable insulation.
      10. Where air-permeable insulation is used and is installed directly below the roof structural sheathing, air shall be supplied at a flow rate greater than or equal to 50 CFM (23.6 L/s) per 1,000 square feet (93 m2) of ceiling. The air shall be supplied from ductwork providing supply air to the occupiable space when the conditioning system is operating. Alternatively, the air shall be supplied by a supply fan when the conditioning system is operating.
        Exceptions:
        1. Where both air-impermeable and air-permeable insulation are used, and the R-value in Table 806.5 is met, air supply to the attic is not required.
        2. Where only air-permeable insulation is used and is installed on top of the attic floor, or on top of the ceiling, air supply to the attic is not required.
    3. 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.
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