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IRC R802 — Wood Roof Framing

Updated Mar 25, 2026
Prescriptive requirements for wood roof framing: rafter sizing, ceiling joist spans, ridge requirements, roof sheathing, and truss installation.

Section R802.4: Rafter spans — Tables R802.4.1(1) through R802.4.1(8) provide maximum spans by species, grade, spacing, and snow load. Common: 2x6 SPF #2 at 16 in o.c. = 11 ft-2 in (20 psf live load). 2x8 = 15 ft-0 in. 2x10 = 19 ft-1 in. 2x12 = 23 ft-3 in. Section R802.5: Ceiling joist spans — similar tables by species, grade, spacing. Section R802.5.1: Ceiling joist bottom chord bracing — continuous lateral restraint at 8 ft intervals. Section R802.3: Ridge board — min 1x nominal, depth ≥ cut end of rafter. Ridge beam: engineered when rafters don't have opposing pairs (cathedral/vaulted). Section R802.7: Roof sheathing — 7/16 OSB or 15/32 plywood typical at 24 in o.c. rafters. Table R803.1 span ratings. Section R802.10: Trusses — designed by registered professional, installed per truss design drawings. Bracing per BCSI-B1. No field modifications without engineer approval.

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IRCresidentialroof-framingraftersceiling-joistssheathingtrusses
DETAILS
code year
2024
code system
IRC
code section
R802
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