Chapter 8 Roof-Ceiling Construction

The provisions of this chapter shall control the design and construction of the roof-ceiling system for all buildings.

Roof and ceiling construction shall be capable of accommodating all loads imposed according to Section R301 and of transmitting the resulting loads to the supporting structural elements.

In areas where expansive or collapsible soils are known to exist, all dwellings shall have a controlled method of water disposal from roofs that will collect and discharge roof drainage to the ground surface at least 5 feet (1524 mm) from foundation walls or to an approved drainage system.

Roof and ceiling framing of wood construction shall be designed and constructed in accordance with the provisions of this section.

Load-bearing dimension lumber for rafters, trusses and ceiling joists shall be identified by a grade mark of a lumber grading or inspection agency that has been approved 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.

Blocking shall be a minimum of utility grade lumber.

Approved end-jointed lumber identified by a grade mark conforming to Section R802.1.1 may 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.

Fire-retardant-treated wood (FRTW) is any wood product which, when impregnated with chemicals by a pressure process or other means during manufacture, shall have, when tested in accordance with ASTM E 84 or UL 723, a listed flame spread index of 25 or less and shows no evidence of significant progressive combustion when the test is continued for an additional 20-minute period. In addition, the flame front shall not progress more than 10.5 feet (3200 mm) beyond the center line of the burners at any time during the test.

R802.1.3.1 Pressure process.
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). R802.1.3.2 Other means during manufacture.
For wood products produced by other means during manufacture the treatment shall be an integral part of the manufacturing process of the wood product. The treatment shall provide permanent protection to all surfaces of the wood product. R802.1.3.3 Testing.
For wood products produced by other means during manufacture, other than a pressure process, all sides of the wood product shall be tested in accordance with and produce the results required in Section R802.1.3. Testing of only the front and back faces of wood structural panels shall be permitted. R802.1.3.4 Labeling.
Fire-retardant-treated lumber and wood structural panels shall be labeled. The label shall contain:

1. The identification mark of an approved agency in accordance with Section 1703.5 of the Florida Building Code, Building.
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 R802.1.3.5 through R802.1.3.8.
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 D 2898).

R802.1.3.5 Strength adjustments.
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 upon an approved method of investigation which 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. R802.1.3.5.1 Wood structural panels.
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 D 5516. The test data developed by ASTM D 5516 shall be used to develop adjustment factors, maximum loads and spans, or both for untreated plywood design values in accordance with ASTM D 6305. Each manufacturer shall publish the allowable maximum loads and spans for service as floor and roof sheathing for their treatment. R802.1.3.5.2 Lumber.
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 D 5664. The test data developed by ASTM D 5664 shall be used to develop modification factors for use at or near room temperature and at elevated temperatures and humidity in accordance with ASTM D 6841. 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. R802.1.3.6 Exposure to weather.
Where fire-retardant-treated wood is exposed to weather or damp or wet locations, it shall be identified as "Exterior" to indicate there is no increase in the listed flame spread index as defined in Section R802.1.3 when subjected to ASTM D 2898. R802.1.3.7 Interior applications.
Interior fire-retardant-treated wood shall have a moisture content of not over 28 percent when tested in accordance with ASTM D 3201 procedures at 92 percent relative humidity. Interior fire-retardant-treated wood shall be tested in accordance with Section R802.1.3.5.1 or R802.1.3.5.2. Interior fire-retardant-treated wood designated as Type A shall be tested in accordance with the provisions of this section. R802.1.3.8 Moisture content.
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 R802.1.3.5.1 for plywood and R802.1.3.5.2 for lumber.

Glued laminated timbers shall be manufactured and identified as required in ANSI/AITC A190.1 and ASTM D 3737.

Stress grading of structural log members of nonrectangular shape, as typically used in log buildings, shall be in accordance with ASTM D 3957. Such structural log members shall be identified by the grade mark of an approved lumber grading or inspection agency. In lieu of a grade mark on the material, a certificate of inspection as to species and grade issued by a lumber-grading or inspection agency meeting the requirements of this section shall be permitted to be accepted.

Structural capacities for structural composite lumber shall be established and monitored in accordance with ASTM D 5456.

Truss design drawings, prepared in conformance to Section R802.1.7.1, shall be provided to the building official and approved prior to installation. Truss design drawings shall include, at a minimum, the information specified below. Truss design drawings shall be provided with the shipment of trusses delivered to the jobsite.

1. Ultimate design wind speed, Vult, and exposure category.
2. Slope or depth, span and spacing.
3. Location of all joints.
4. Required bearing widths.
5. 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.
6. Adjustments to lumber and joint connector design values for conditions of use.
7. Each reaction force and direction.
8. Joint connector type and description (e.g., size, thickness or gage) and the dimensioned location of each joint connector except where symmetrically located relative to the joint interface.
9. Lumber size, species and grade for each member.
10. Connection requirements for:
    1. Truss to girder-truss.
    2. Truss ply to ply.
    3. Field splices.
11. Calculated deflection ratio and/or maximum description for live and total load.
12. 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.
13. 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 professional where required by Florida Statues.

Reserved.

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 (e.g., 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.

Trusses shall be connected to wall plates by the use of approved connectors having a resistance to design uplift, lateral and shear forces. Trusses shall be installed in accordance with the manufacturer's design and specifications.

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 R502.1.11.1 except that cantilevered portions of rafters shall be permitted in accordance with Section R802.1.8.1.1.

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 R802.1.8.1.1.

For SI: 1 inch = 25.4 mm.

Taper cuts at the ends of the ceiling joist shall not exceed one-fourth the depth of the member in accordance with Figure R802.1.8.1.2.

Cuts, notches and holes bored in trusses, structural composite lumber, structural glue-laminated 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-ceilings of lightframe wood construction shall be designed and constructed in accordance with the provisions of Sections R301.2.1.1 and R802.1.

1. For rafter connections to the top plate, straps and/or clips shall extend such that the top nail is within 1 inch (25.4 mm) of the top of the rafter with one or more nails installed on the opposite side of the rafter.
2. Roof sheathing shall be at a minimum attached in accordance with Section R803.2.3.

Reserved.

Reserved.

Reserved.

Reserved.

Table R802.4(1) Ceiling Joist Spans For Common Lumber Species (Uninhabitable attics without storage, live load = 10 psf, L/Δ = 240).
Reserved.

Table R802.4(2) Ceiling Joist Spans For Common Lumber Species (Uninhabitable attics with limited storage, live load = 20 psf, L/Δ = 240).
Reserved.

Reserved.

Reserved.

Table R802.5.1(1) Rafter Spans For Common Lumber Species (Roof live load = 20 psf, ceiling not attached to rafters, L/Δ = 180).
Reserved.

Table R802.5.1(2) Rafter Spans For Common Lumber Species (Roof live load = 20 psf, ceiling attached to rafters, L/Δ = 240).
Reserved.

Table R802.5.1(3) Rafter Spans For Common Lumber Species (Ground snow load = 30 psf, ceiling not attached to rafters, L/Δ = 180).
Reserved.

Table R802.5.1(4) Rafter Spans For Common Lumber Species (Ground snow load = 50 psf, ceiling not attached to rafters, L/Δ = 180).
Reserved.

Table R802.5.1(5) Rafter Spans For Common Lumber Species (Ground snow load = 30 psf, ceiling attached to rafters, L/Δ = 240).
Reserved.

Table R802.5.1(6) Rafter Spans For Common Lumber Species (Ground snow load = 50 psf, ceiling attached to rafters, L/Δ = 240).
Reserved.

Table R802.5.1(7) Rafter Spans For 70 PSF Ground Snow Load (Ceiling not attached to rafters, L/Δ = 180).
Reserved.

Table R802.5.1(8) Rafter Spans For 70 PSF Ground Snow Load (Ceiling attached to rafters, L/Δ = 240).
Reserved.

Table R802.5.1(9) Rafter/Ceiling Joist Heel Joint Connections.
Reserved.

Figure R802.5.1 Braced Rafter Construction.
Reserved.

Reserved.

Reserved.

(Moved to Section R802.1.8.)

Reserved.

Reserved.

Reserved.

(Moved to Section R802.1.7.)

Reserved.

Table R802.11 Rafter or Truss Uplift Connection Forces from wind (Pounds per Connection).

Reserved.

Reserved.

Reserved.

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

1. Minimum 270 F_b, 340,000 E.
2. Minimum 420 F_b, 660,000 E.
3. Minimum 600F_b, 1,150,000 E.

Wood structural panels shall conform to DOC PS 1, DOC PS 2 or, when manufactured in Canada, CSA O437 or CSA O325, and shall be identified for grade, bond classification, and Performance Category by a grade mark or certificate of inspection issued by an approved agency. Wood structural panels shall comply with the grades specified in Table R503.2.1.1(1).

All 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 may 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 in accordance with Section R803.2.3.1 for wood roof framing or in accordance with AISI 230 for steel roof framing.

Wood structural panel sheathing shall be fastened to roof framing with 8d annular ring-shank nails at 6 inches (152 mm) on center at edges and 6 inches (152 mm) on center at intermediate framing. Ring-shank nails shall have the following minimum dimensions:

1. 0.113 inch nominal root shank diameter
2. Ring diameter of 0.010 over shank diameter
3. 16 to 20 rings per inch
4. 0.280 inch full round head diameter
5. 2-³/₈ inch nail length

For SI: 1 inch = 25.4 mm.

Ceilings shall be installed in accordance with the requirements for interior wall finishes as provided in Section R702.