• Codes
  • Features

    Features Overview

    Go to features
    Reference

    Reference.

    A reliable and up-to-date source of codes.
    Research

    Research.

    Rapidly and efficiently calculate project parameters.
    Collaboration

    Collaboration.

    Get everyone on the same page and streamline code research.
    Workflows
    Architects General Contractor Building Official & Plans Examiner Inspectors Owner Subcontractors Code Consultants
  • Pricing
  • Login
  • Sign Up
Sign Up
Login
  • Code Library
  • Features
  • Pricing
  • About
  • Careers
  • Help
  • Contact
  • Terms
  • Privacy
Sign Up
Upgrade to Premium
Code calculators: Code Calculators automatically generates a detailed list of requirements.
REFERENCE
Amendment Styling
Industry-leading search
Code diagrams
RESEARCH
Code calculators
Filter by topic
Code compare
Code sheet exports
COLLABORATION
Team projects
Bookmarks
Comments
START 2 WEEK FREE TRIAL
Have an account? Sign in
// CODE SNIPPET

2304.8 Floor and Roof Sheathing

Building Code 2018 of Illinois > 23 Wood > 2304 General Construction Requirements > 2304.8 Floor and Roof Sheathing
JUMP TO FULL CODE CHAPTER

Structural floor sheathing and structural roof sheathing shall comply with Sections 2304.8.1 and 2304.8.2, respectively.

TABLE 2304.8(1)

ALLOWABLE SPANS FOR LUMBER FLOOR AND ROOF SHEATHING

SPAN (inches)MINIMUM NET THICKNESS (inches) OF LUMBER PLACED
Perpendicular to supportsDiagonally to supports
Surfaced dryaSurfaced unseasonedSurfaced dryaSurfaced unseasoned
Floors
243/425/323/425/32
165/811/165/811/16
Roofs
245/811/163/425/32

For SI: 1 inch = 25.4 mm.

  1. Maximum 19-percent moisture content.

TABLE 2304.8(2)

SHEATHING LUMBER, MINIMUM GRADE REQUIREMENTS: BOARD GRADE

SOLID FLOOR OR ROOF SHEATHINGSPACED ROOF SHEATHINGGRADING RULES
UtilityStandardNLGA, WCLIB, WWPA
4 common or utility3 common or standardNLGA, WCLIB, WWPA, NSLB or NELMA
No. 3No. 2SPIB
MerchantableConstruction commonRIS

TABLE 2304.8(3)

ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANEL SHEATHING AND SINGLE-FLOOR GRADES CONTINUOUS OVER TWO OR MORE SPANS WITH STRENGTH AXIS PERPENDICULAR TO SUPPORTSa

SHEATHING GRADESROOFbFLOORc
Panel span rating roof/
floor span
Panel thickness
(inches)
Maximum span (inches)Loadd(psf)Maximum span
(inches)
With edge supporteWithout edge supportTotal loadLive load
16/03/8161640300
20/03/8202040300
24/03/8, 7/16, 1/22420f40300
24/167/16, 1/22424504016
32/1615/32, 1/2, 5/83228403016g
40/2019/32, 5/8, 3/4, 7/84032403020g,h
48/2423/32, 3/4, 7/84836453524
54/327/8, 15440453532
60/327/8, 11/86048453532
SINGLE FLOOR GRADESROOFbFLOORc
Panel span ratingPanel thickness
(inches)
Maximum span (inches)Loade (psf)Maximum span
(inches)
With edge supporteWithout edge supportTotal loadLive load
16 o.c.1/2, 19/32, 5/82424504016g
20 o.c.19/32, 5/8, 3/43232403020g,h
24 o.c.23/32, 3/44836352524
32 o.c.7/8, 14840504032
48 o.c.13/32, 11/86048504048

For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.

  1. Applies to panels 24 inches or wider.
  2. Uniform load deflection limitations 1/180 of span under live load plus dead load, 1/240 under live load only.
  3. Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking unless 1/4-inch minimum thickness underlayment or 11/2 inches of approved cellular or lightweight concrete is placed over the subfloor, or finish floor is 3/4-inch wood strip. Allowable uniform load based on deflection of 1/360 of span is 100 pounds per square foot except the span rating of 48 inches on center is based on a total load of 65 pounds per square foot.
  4. Allowable load at maximum span.
  5. Tongue-and-groove edges, panel edge clips (one midway between each support, except two equally spaced between supports 48 inches on center), lumber blocking or other. Only lumber blocking shall satisfy blocked diaphragm requirements.
  6. For 1/2-inch panel, maximum span shall be 24 inches.
  7. Span is permitted to be 24 inches on center where 3/4-inch wood strip flooring is installed at right angles to joist.
  8. Span is permitted to be 24 inches on center for floors where 11/2 inches of cellular or lightweight concrete is applied over the panels.

TABLE 2304.8(4)

ALLOWABLE SPAN FOR WOOD STRUCTURAL PANEL COMBINATION SUBFLOOR-UNDERLAYMENT (SINGLE FLOOR)a (Panels Continuous Over Two or More Spans and Strength Axis Perpendicular to Supports)

IDENTIFICATIONMAXIMUM SPACING OF JOISTS (inches)
1620243248
Species groupbThickness (inches)
11/25/83/4——
2, 35/83/47/8——
43/47/81——
Single floor span ratingc16 o.c.20 o.c.24 o.c.32 o.c.48 o.c.

For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.

  1. Spans limited to value shown because of possible effects of concentrated loads. Allowable uniform loads based on deflection of 1/360 of span is 100 pounds per square foot except allowable total uniform load for 11/8-inch wood structural panels over joists spaced 48 inches on center is 65 pounds per square foot. Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking, unless 1/4-inch minimum thickness underlayment or 11/2 inches of approved cellular or lightweight concrete is placed over the subfloor, or finish floor is 3/4-inch wood strip.
  2. Applicable to all grades of sanded exterior-type plywood. See DOC PS 1 for plywood species groups.
  3. Applicable to Underlayment grade, C-C (Plugged) plywood, and Single Floor grade wood structural panels.

TABLE 2304.8(5)

ALLOWABLE LOAD (PSF) FOR WOOD STRUCTURAL PANEL ROOF SHEATHING CONTINUOUS OVER TWO OR MORE SPANS AND STRENGTH AXIS PARALLEL TO SUPPORTS (Plywood structural panels are five-ply, five-layer unless otherwise noted)a

PANEL GRADETHICKNESS (inch)MAXIMUM SPAN (inches)LOAD AT MAXIMUM SPAN (psf)
LiveTotal
Structural I sheathing7/16242030
15/322435b45b
1/22440b50b
19/32, 5/8247080
23/32, 3/42490100
Sheathing, other grades covered
in DOC PS 1 or DOC PS 2
7/16164050
15/32242025
1/2242530
19/322440b50b
5/82445b55b
23/32, 3/42460b65b

For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.

  1. Uniform load deflection limitations 1/180 of span under live load plus dead load, 1/240 under live load only. Edges shall be blocked with lumber or other approved type of edge supports.
  2. For composite and four-ply plywood structural panel, load shall be reduced by 15 pounds per square foot.

2304.8.1 Structural Floor Sheathing

Structural floor sheathing shall be designed in accordance with the general provisions of this code.

Floor sheathing conforming to the provisions of Table 2304.8(1), 2304.8(2), 2304.8(3) or 2304.8(4) shall be deemed to meet the requirements of this section.

2304.8.2 Structural Roof Sheathing

Structural roof sheathing shall be designed in accordance with the general provisions of this code and the special provisions in this section.

Roof sheathing conforming to the provisions of Table 2304.8(1), 2304.8(2), 2304.8(3) or 2304.8(5) shall be deemed to meet the requirements of this section. Wood structural panel roof sheathing shall be of a type manufactured with exterior glue (Exposure 1 or Exterior).

Related Code Sections


2304.8 Wood, Floor and Roof Sheathing
Structural floor sheathing and structural roof sheathing shall comply with Sections 2304.8.1 and 2304.8.2, respectively. TABLE 2304.8(1 ...
Building Code 2018 of Illinois > 23 Wood > 2304 General Construction Requirements > 2304.8 Floor and Roof Sheathing
708.4.2 Fire and Smoke Protection Features, Fireblocks and Draftstops in Combustible Construction
In combustible construction where fire partitions do not extend to the underside of the floor or roof sheathing, deck or slab above, the space ...
Building Code 2018 of Illinois > 7 Fire and Smoke Protection Features > 708 Fire Partitions > 708.4 Continuity > 708.4.2 Fireblocks and Draftstops in Combustible Construction
710.4 Fire and Smoke Protection Features, Continuity
Smoke partitions shall extend from the top of the foundation or floor below to the underside of the floor or roof sheathing, deck or slab above ...
Building Code 2018 of Illinois > 7 Fire and Smoke Protection Features > 710 Smoke Partitions > 710.4 Continuity
707.8 Fire and Smoke Protection Features, Joints
or roof sheathing, slab or deck above, and the exterior vertical wall intersection shall comply with Section 715 ...
Building Code 2018 of Illinois > 7 Fire and Smoke Protection Features > 707 Fire Barriers > 707.8 Joints
2303.2.5.1 Wood, Wood Structural Panels
publish the allowable maximum loads and spans for service as floor and roof sheathing for its treatment ...
Building Code 2018 of Illinois > 23 Wood > 2303 Minimum Standards and Quality > 2303.2 Fire-Retardant-Treated Wood > 2303.2.5 Strength Adjustments > 2303.2.5.1 Wood Structural Panels
Help Contact Us Privacy Terms
Search
Search
Don't miss relevant code. Quickly locate sections across your jurisdiction.
Code Calculators
Code Calculators
Code calculators automatically generate a detailed list of requirements.
Code sheet exports
Code sheet exports
Generate a code sheet that integrates with your drawing set.
Code diagrams
Code diagrams
Unpack the code through illustrations and descriptions.
Shared projects
Shared projects
Projects provide a dedicated space to collaborate on code research.
Code Compare
Code Compare
Highlight differences between any two building codes.
UpCodes Premium
Leverage the most sophisticated code compliance platform.
TRY FREE FOR TWO WEEKS VISIT PRICING
UpCodes Premium
Leverage the full code compliance platform.
START 2 WEEK FREE TRIAL LEARN MORE