Section R503 — FLOOR SHEATHING
2025 California Residential Code (Title 24, Part 2.5) · 2025 edition · ingested 2026-07-07 · California
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R503.1 Lumber sheathing. ¶
R503.1 Lumber sheathing. 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). TABLE R503.1—MINIMUM THICKNESS OF LUMBER FLOOR SHEATHINGCol2Col3 --------- JOIST OR BEAM SPACING<br(inches)MINIMUM NET THICKNESSMINIMUM NET THICKNESS JOIST OR BEAM SPACING<br(inches)Perpendicular to joistDiagonal to joist 2411/163/4 165/85/8 48a11/2 T & GN/A 54b54b54b 60c60c60c For SI: 1 inch = 25.4 mm, 1 pound per square inch = 6.895 kPa.<brN/A = Not Applicable.<bra. For this support spacing, lumber sheathing shall have a minimumFb of 675 and…
R503.2 Wood structural panel sheathing. ¶
R503.2 Wood structural panel sheathing. R503.2.1 Identification and grade. Wood structural panel sheathing used for structural purposes shall conform to CSA O325, CSA O437 DOC PS 1 or DOC PS 2. 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” wherever referenced in this code. R503.2.1.1 Subfloor and combined subfloor underlayment. Where used as subflooring or combination subfloor…
R503.3 Particleboard. ¶
R503.3 Particleboard. R503.3.1 Identification and grade. Particleboard shall conform to ANSI A208.1 and shall be so identified by a grade mark or certificate of inspection issued by an approved agency. R503.3.2 Floor underlayment. Particleboard floor underlayment shall conform to Type PBU and shall be not less than [1] / 4 inch (6.4 mm) in thickness. R503.3.3 Installation. Particleboard underlayment shall be installed in accordance with the recommendations of the manufacturer and attached to framing in accordance with Table R602.3(1).