The provisions of this chapter shall control the design and construction of the roof-ceiling system for all buildings.
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.
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.
5.1. Top chord live load (as determined from Section R301.6).
5.2. Top chord dead load.
5.3. Bottom chord live load.
5.4. Bottom chord dead load.
5.5. Concentrated loads and their points of application.
5.6. 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:
10.1. Truss to girder-truss.
10.2. Truss ply to ply.
10.3. 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.
R802.1.7.2 [IRC 802.10.2] Design.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. R802.1.7.2.1 [IRC 802.10.2.1] Applicability limits.
Reserved. R802.1.7.3 [IRC 802.10.3] Bracing.
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. R802.1.7.4 [IRC 802.10.4] Alterations to 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. R802.1.7.5 Truss to wall connection.
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.
R802.1.8.1 [IRC 802.7.1] Sawn lumber.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 R802.1.8.1.1 [IRC R802.7.1.1] Cantilevered portions of rafters.
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.
FIGURE R802.1.8.1.1 [IRC 802.7.1.1]
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 R802.1.8.1.2.
FIGURE R802.1.8.1.2 [IRC R.802.7.1.2]
CEILING JOIST TAPER CUT
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.
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.
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.
Table R802.11 Rafter or Truss Uplift Connection Forces from wind (Pounds per Connection).
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 |
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).
R803.2.1.1 Exposure durability.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. R803.2.1.2 Fire-retardant-treated plywood.
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.
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.
R803.2.3.1 Sheathing fastenings.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
1. Where roof framing with a specific gravity, 0.42 ≤G < 0.49 is used, spacing of ring-shank fasteners shall be permitted at 12 inches (305 mm) on center at intermediate framing in nailing zone 1 for any Vult and in nailing zone 2 for Vult less than or equal to 140 mph in accordance with Figure R803.2.3.1.
2. Where roof framing with a specific gravity, G =0.49 is used, spacing of ring-shank fasteners shall be permitted at 12 inches (305 mm) on center at intermediate framing in nailing zone 1 for any Vult and in nailing zone 2 for Vult less than or equal to 150 mph in accordance with Figure R803.2.3.1.
3. Where roof framing with a specific gravity, G =0.49 is used, 8d common or 8d hot dipped galvanized box nails at 6 inches (152 mm) on center at edges and 6 inches (152 mm) on center at intermediate framing shall be permitted for Vult less than or equal to 130 mph in accordance with Figure R803.2.3.1.
4. Where roof diaphragm requirements necessitate a closer fastener spacing.
FIGURE R803.2.3.1
ROOF SHEATHING NAILING ZONES
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, 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 R802.1.8. Required ventilation openings shall open directly to the outside air.
The minimum net free ventilating area shall be 1/150 of the area of the vented space.
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. At least 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 no more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically, with the balance of the required ventilation provided by eave or cornice vents. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet (914 mm) below the ridge or highest point of the space shall be permitted.
Unvented attic assemblies (spaces between the ceiling joists of the top story and the roof rafters) and unvented enclosed rafter assemblies (spaces between ceilings that are applied directly to the underside of roof framing members/rafters and the structural roof sheathing at the top of the roof framing members/rafters) shall be permitted if all the following conditions are met:
1. The unvented attic space is completely contained within the building thermal envelope.
2. No interior Class I vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed rafter assembly.
3. Where wood shingles or shakes are used, a minimum 1/4-inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing.
4. In Climate Zones 5, 6, 7 and 8 of Table R301.1 of the Florida Building Code, Energy Conservation, any air impermeable insulation shall be a Class II vapor retarder, or shall have a Class III vapor retarder coating or covering in direct contact with the underside of the insulation.
5. Either Items 5.1, 5.2 or 5.3 shall be met, depending on the air permeability of the insulation directly under the structural roof sheathing.
5.1. Air-impermeable insulation only. Insulation shall be applied in direct contact with the underside of the structural roof sheathing.
5.2. Air-permeable insulation only. In addition to the air-permeable insulation installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing as specified in Table R806.5 for condensation control.
5.3. Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing as specified in Table R806.5 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.
5.4. Where preformed insulation board is used as the air-impermeable insulation layer, it shall be sealed at the perimeter of each individual sheet interior surface to form a continuous layer.
TABLE R806.5
INSULATION FOR CONDENSATION CONTROL
| CLIMATE ZONE | MINIMUM RIGID BOARD ON AIR- IMPERMEABLE INSULATION R-VALUEa |
| 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 |
Buildings with combustible ceiling or roof construction shall have an attic access opening to attic areas that exceed 30 square feet (2.8 m2) and have a vertical height of 30 inches (762 mm) or greater. The vertical height shall be measured from the top of the ceiling framing members to the underside of the roof framing members.
The rough-framed opening shall not be less than 22 inches by 30 inches (559 mm by 762 mm) and shall be located in a hallway or other readily accessible location. When located in a wall, the opening shall be a minimum of 22 inches wide by 30 inches high (559 mm wide by 762 mm high). When the access is located in a ceiling, minimum unobstructed headroom in the attic space shall be 30 inches (762 mm) at some point above the access measured vertically from the bottom of ceiling framing members. See Section M1305.1.3 for access requirements where mechanical equipment is located in attics.