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 located directly over a space protected by an automatic sprinkler system in accordance with Section P2904, NFPA13D, or other approved equivalent sprinkler system.
- Floor assemblies located directly over a crawl space not intended for storage or fuel-fired appliances.
- Portions of floor assemblies can be unprotected when complying with the following:
- 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.
- Slope or depth, span and spacing.
- Location of all joints.
- Required bearing widths.
- Design loads as applicable:
- Top chord live load;
- Top chord dead load;
- Bottom chord live load;
- Bottom chord dead load;
- Concentrated loads and their points of application; and
- Controlling wind and earthquake loads.
- Adjustments to lumber and joint connector design values for conditions of use.
- Each reaction force and direction.
- 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.
- Lumber size, species and grade for each member.
- Connection requirements for:
- Truss ply-to-ply; and
- Field splices.
- Calculated deflection ratio and/or maximum description for live and total load.
- 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.
- 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.
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|
- For this support spacing, lumber sheathing shall have a minimum Fb of 675 and minimum E of 1,100,000 (see AF&PA/NDS).
- For this support spacing, lumber sheathing shall have a minimum Fb of 765 and minimum E of 1,400,000 (see AF&PA/NDS).
- For this support spacing, lumber sheathing shall have a minimum Fb of 855 and minimum E of 1,700,000 (see AF&PA/NDS).
|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|
- The allowable total loads were determined using a dead load of 10 psf. If the dead load exceeds 10 psf, then the live load shall be reduced accordingly.
- Panels continuous over two or more spans with long dimension (strength axis) perpendicular to supports. Spans shall be limited to values shown because of possible effect of concentrated loads.
- Applies to panels 24 inches or wider.
- Lumber blocking, panel edge clips (one midway between each support, except two equally spaced between supports when span is 48 inches), tongue-and-groove panel edges, or other approved type of edge support.
- Includes Structural I panels in these grades.
- Uniform load deflection limitation: 1/180 of span under live load plus dead load, 1/240 of span under live load only.
- Maximum span 24 inches for 15/32-and 1/2-inch panels.
- Maximum span 24 inches where 3/4-inch wood finish flooring is installed at right angles to joists.
- Maximum span 24 inches where 1.5 inches of lightweight concrete or approved cellular concrete is placed over the subfloor.
- Unsupported edges shall have tongue-and-groove joints or shall be supported with blocking unless minimum nominal 1/4-inch thick underlayment with end and edge joints offset at least 2 inches or 1.5 inches of lightweight concrete or approved cellular concrete is placed over the subfloor, or 3/4-inch wood finish flooring is installed at right angles to the supports. Allowable uniform live load at maximum span, based on deflection of 1/360 of span, is 100 psf.
- Unsupported edges shall have tongue-and-groove joints or shall be supported by blocking unless nominal 1/4-inch-thick underlayment with end and edge joints offset at least 2 inches or 3/4-inch wood finish flooring is installed at right angles to the supports. Allowable uniform live load at maximum span, based on deflection of 1/360 of span, is 100 psf, except panels with a span rating of 48 on center are limited to 65 psf total uniform load at maximum span.
- Allowable live load values at spans of 16" o.c. and 24" o.c taken from reference standard APA E30, APA Engineered Wood Construction Guide. Refer to reference standard for allowable spans not listed in the table.
|IDENTIFICATION||SPACING OF JOISTS (inches)|
- Plywood continuous over two or more spans and face grain perpendicular to supports. Unsupported edges shall be tongue-and-groove or blocked except where nominal 1/4-inch-thick underlayment or 3/4-inch wood finish floor is used. Allowable uniform live load at maximum span based on deflection of 1/360 of span is 100 psf.
- Applicable to all grades of sanded exterior-type plywood.
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.
- From garages, utility buildings and other unheated accessory structures.
- For unheated storage rooms having an area of less than 70 square feet (6.5 m2) and carports.
- From driveways, walks, patios and other flatwork not likely to be enclosed and heated at a later date.
- 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.
|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 tip of the lag screw shall fully extend beyond the inside face of the band joist.
- The maximum gap between the face of the ledger board and face of the wall sheathing shall be 1/2 inch.
- Ledgers shall be flashed to prevent water from contacting the house band joist.
- Lag screws and bolts shall be staggered in accordance with Section R507.2.1.
- Deck ledger shall be minimum 2 × 8 pressure-preservative-treated No. 2 grade lumber, or other approved materials as established by standard engineering practice.
- When solid-sawn pressure-preservative-treated deck ledgers are attached to a minimum 1-inch-thick engineered wood product (structural composite lumber, laminated veneer lumber or wood structural panel band joist), the ledger attachment shall be designed in accordance with accepted engineering practice.
- A minimum 1 × 91/2 Douglas Fir laminated veneer lumber rimboard shall be permitted in lieu of the 2-inch nominal band joist.
- Wood structural panel sheathing, gypsum board sheathing or foam sheathing not exceeding 1 inch in thickness shall be permitted. The maximum distance between the face of the ledger board and the face of the band joist shall be 1 inch.
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|
- Lag screws or bolts shall be staggered from the top to the bottom along the horizontal run of the deck ledger in accordance with Figure R507.2.1(1).
- Maximum 5 inches.
- For engineered rim joists, the manufacturer's recommendations shall govern.
- The minimum distance from bottom row of lag screws or bolts to the top edge of the ledger shall be in accordance with Figure R507.2.1(1).
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