The provisions of this chapter shall control the design and construction of the floors for all buildings including the floors of attic spaces used to house mechanical or plumbing fixtures and equipment.
Floor assemblies, not required elsewhere in this code to be fire-resistance rated, shall be provided with a 1/2-inch (12.7 mm) gypsum wallboard membrane, 5/8-inch (16 mm) wood structural panel membrane, or equivalent on the underside of the floor framing member.
1. Floor assemblies located directly over a space protected by an automatic sprinkler system in accordance with Section P2904, NFPA13D, or other approved equivalent sprinkler system.
2. Floor assemblies located directly over a crawl space not intended for storage or fuel-fired appliances.
3. Portions of floor assemblies can be unprotected when complying with the following:
3.1. The aggregate area of the unprotected portions shall not exceed 80 square feet per story.
3.2. Fire blocking in accordance with Section R302.11.1 shall be installed along the perimeter of the unprotected portion to separate the unprotected portion from the remainder of the floor assembly.
4. Wood floor assemblies using dimension lumber or structural composite lumber equal to or greater than 2-inch by 10-inch (50.8 mm by 254 mm) nominal dimension, or other approved floor assemblies demonstrating equivalent fire performance.
Wood trusses shall be designed in accordance with approved 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 Statutes. R502.1.10.2 [IRC 502.11.2] 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 TPI/WTCA BCSI. R502.1.10.3 [IRC 502.11.3] Alterations to trusses.
Truss members and components shall not be cut, notched, 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, etc.), that exceed the design load for the truss, shall not be permitted without verification that the truss is capable of supporting the additional loading. R502.1.10.4 [IRC 502.11.4] Truss design drawings.
Truss design drawings, prepared in compliance with Section R502.1.10.1, shall be submitted 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 information specified below:
1. Slope or depth, span and spacing.
2. Location of all joints.
3. Required bearing widths.
4. Design loads as applicable:
4.1. Top chord live load;
4.2. Top chord dead load;
4.3. Bottom chord live load;
4.4. Bottom chord dead load;
4.5. Concentrated loads and their points of application; and
4.6. Controlling wind and earthquake loads.
5. Adjustments to lumber and joint connector design values for conditions of use.
6. Each reaction force and direction.
7. Joint connector type and description, e.g., size, thickness or gauge, and the dimensioned location of each joint connector except where symmetrically located relative to the joint interface.
8. Lumber size, species and grade for each member.
9. Connection requirements for:
9.2. Truss ply-to-ply; and
9.3. Field splices.
10. Calculated deflection ratio and/or maximum description for live and total load.
11. Maximum axial compression forces in the truss members to enable the building designer to design the size, connections and anchorage of the permanent continuous lateral bracing. Forces shall be shown on the truss drawing or on supplemental documents.
12. Required permanent truss member bracing location.
Structural floor members shall not be cut, bored or notched in excess of the limitations specified in this section. See Figure R502.1.11.
FIGURE R502.1.11 [IRC 502.8]
CUTTING, NOTCHING AND DRILLING
Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members. The diameter of holes bored or cut into members shall not exceed one-third the depth of the member. Holes shall not be closer than 2 inches (51 mm) to the top or bottom of the member, or to any other hole located in the member. Where the member is also notched, the hole shall not be closer than 2 inches (51 mm) to the notch. R502.1.11.2 [IRC 502.8.2] Engineered wood products.
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.
Floor framing of light-frame wood construction shall be designed and constructed in accordance with the provisions of Section R301.2.1.1 or in accordance with the AF&PA NDS. Floor framing of light-frame wood construction shall also comply with Sections R317, R318 and R502.1.
Figure R502.2 Floor construction.
Table R502.3.1(1) Floor joist spans for common lumber species.
Table R502.3.1(2) Floor joist spans for common lumber species.
Table R502.3.3(1) Cantilever spans for floor joists supporting light-frame exterior bearing wall and roof only.
Table R502.3.3(2) Cantilever spans for floor joists supporting exterior balcony.
Table R502.5(1) Girder spans and header spans for exterior bearing walls.
Table R502.5(2) Girder spans and header spans for interior bearing walls.
Maximum allowable spans for lumber used as floor sheathing shall conform to Tables R503.1, R503.2.1.1(1) and R503.2.1.1(2).
MINIMUM THICKNESS OF LUMBER FLOOR SHEATHING
|JOIST OR BEAM|
|MINIMUM NET THICKNESS|
|Perpendicular to joist||Diagonal to joist|
|48a||11/2 T & G||N/A|
Wood structural panel sheathing used for structural purposes shall conform to DOC PS 1, DOC PS 2 or, when manufactured in Canada, CSA O437 or CSA O325. All panels shall be identified for grade, bond classification, and Performance Category by a grade mark or certificate of inspection issued by an approved agency. The Performance Category value shall be used as the “nominal panel thickness” or “panel thickness” whenever referenced in this code.R503.2.1.1 Subfloor and combined subfloor underlayment.
Where used as subflooring or combination subfloor underlayment, wood structural panels shall be of one of the grades specified in Table R503.2.1.1(1). When sanded plywood is used as combination subfloor underlayment, the grade, bond classification, and Performance Category shall be as specified in Table R503.2.1.1(2).
ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANELS FOR ROOF AND
SUBFLOOR SHEATHING AND COMBINATION SUBFLOOR UNDERLAYMENTa, b, c
|SPAN RATING||MINIMUM NOMINAL PANEL THICKNESS |
|ALLOWABLE LIVE LOAD (psf)h, I||MAXIMUM SPAN |
|LOAD (pounds per square foot, at maximum span)||MAXIMUM |
@ 16″ o.c.
@ 24″ o.c.
|With edge supportd||Without edge support||Total load||Live load|
|40/20||19/32, 5/8||305||130||40||32||40||30||20h, i|
|Underlayment, C-C plugged, |
|Rooff||Combination subfloor underlaymentk|
|16 o.c.||19/32, 5/8||100||40||24||24||50||40||16i|
|20 o.c.||19/32, 5/8||150||60||32||32||40||30||20i, j|
|24 o.c.||23/32, 3/4||240||100||48||36||35||25||24|
|48 o.c.||13/32, 11/8||—||290||60||48||50||40||48|
ALLOWABLE SPANS FOR SANDED PLYWOOD
COMBINATION SUBFLOOR UNDERLAYMENTa
|IDENTIFICATION||SPACING OF JOISTS (inches)|
A 4-inch-thick (102 mm) base course consisting of clean graded sand, gravel, crushed stone or crushed blast-furnace slag passing a 2-inch (51 mm) sieve shall be placed on the prepared subgrade when the slab is below grade.
A 6-mil (0.006 inch; 152 μm) polyethylene or approved vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the concrete floor slab and the base course or the prepared subgrade where no base course exists.
1. From garages, utility buildings and other unheated accessory structures.
2. For unheated storage rooms having an area of less than 70 square feet (6.5 m2) and carports.
3. From driveways, walks, patios and other flatwork not likely to be enclosed and heated at a later date.
4. Where approved by the building official, based on local site conditions.
For decks supporting a total design load of 50 pounds per square foot (2394 Pa) [40 pounds per square foot (1915 Pa) live load plus 10 pounds per square foot (479 Pa) dead load], the connection between a deck ledger of pressure-preservative-treated Southern Pine, incised pressure-preservative-treated Hem-Fir or approved decay-resistant species, and a 2-inch (51 mm) nominal lumber band joist bearing on a sill plate or wall plate shall be constructed with 1/2-inch (12.7 mm) lag screws or bolts with washers in accordance with Table R507.2. Lag screws, bolts and washers shall be hot-dipped galvanized or stainless steel.
FASTENER SPACING FOR A SOUTHERN PINE OR HEM-FIR DECK LEDGER AND
A 2-INCH-NOMINAL SOLID-SAWN SPRUCE-PINE-FIR BAND JOISTc, f, g
(Deck live load = 40 psf, deck dead load = 10 psf)
|JOIST SPAN||6' and less||6'1" to 8'||8'1" to 10'||10'1" to 12'||12'1" to 14'||14'1" to 16'||16'1" to 18'|
|Connection details||On-center spacing of fastenersd, e|
|1/2 inch diameter lag screw with 15/32 inch maximum sheathinga||30||23||18||15||13||11||10|
|1/2 inch diameter bolt with 15/32 inch maximum sheathing||36||36||34||29||24||21||19|
|1/2 inch diameter bolt with 15/32 inch maximum sheathing and 1/2 inch stacked washersb, h||36||36||29||24||21||18||16|
The lag screws or bolts in deck ledgers and band joists shall be placed in accordance with Table R507.2.1 and Figures R507.2.1(1) and R507.2.1(2).
PLACEMENT OF LAG SCREWS AND BOLTS IN DECK LEDGERS AND BAND JOISTS
|MINIMUM END AND EDGE DISTANCES AND SPACING BETWEEN ROWS|
|TOP EDGE||BOTTOM EDGE||ENDS||ROW SPACING|
|Ledgera||2 inchesd||3/4 inch||2 inchesb||15/8 inchesb|
|Band Joistc||3/4 inch||2 inches||2 inchesb||15/8 inchesb|
PLACEMENT OF LAG SCREWS AND BOLTS IN LEDGERS
PLACEMENT OF LAG SCREWS AND BOLTS IN BAND JOISTS
The lateral load connection required by Section R507.1 shall be permitted to be in accordance with Figure R507.2.3. Where the lateral load connection is provided in accordance with Figure 507.2.3, hold-down tension devices shall be installed in not less than two locations per deck, and each device shall have an allowable stress design capacity of not less than 1500 pounds (6672 N).
DECK ATTACHMENT FOR LATERAL LOADS