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Detached houses, duplexes and townhouses up to 3 stories with their own exits use the IRC; every other building uses the IBC (IBC 101.2).
30 sections matching “R302.1” for San Antonio, TX, the 2024 IRC
R302.1
Exterior Walls
Used in checks
An unsprinklered house's exterior walls closer than 5 ft to the lot line need a 1-hour rating, tested from both sides.
Unsprinklered: no projections within 2 ft of the line; 1-hour underside from 2 to under 5 ft; unrated at 5 ft or more.
Unsprinklered: no wall openings within 3 ft; up to 25% of the wall at 3 ft to under 5 ft; unlimited at 5 ft or more.
Penetrations within 3 ft of the lot line are protected per R302.4.
A fully sprinklered house only needs rated walls (tested from outside) under 3 ft; openings are unlimited from 3 ft and projections can be rated from 2 ft.
In a fully sprinklered subdivision, the separation distance can drop to 0 ft where the neighbouring lot keeps an open yard of 6 ft or more.
Two homes on one lot measure to an imaginary line between them; townhouses measure to the lot line or an imaginary line.
Exempt: walls perpendicular to the line, the owner's own accessory buildings, permit-exempt sheds, and foundation vents. A detached garage within 2 ft of the line may have eaves of up to 4 in.
Wood framing gets fireblocking at every floor and ceiling line, every 10 ft horizontally, at soffits and drop ceilings, at stair stringer ends and around penetrations.
With usable space above and below, draftstops keep concealed floor-ceiling spaces at 1,000 sq ft or less where the ceiling is suspended or the floor uses open-web trusses.
Unrated floors get 1/2 in gypsum or 5/8 in wood panel under the framing, unless sprinklered below, over a plain crawl space, built of 2x10 or larger lumber, or a small detached accessory floor.
Fire-retardant-treated wood has a flame spread index of 25 or less, and in an extended 20-minute test the flame front stays within 10.5 ft.
Each FRTW piece is labelled, and is dried to 19% moisture or less for lumber and 15% or less for panels; interior FRTW stays at or below 28% at 92% humidity.
Accepted fireblocks include 2 in lumber, doubled 1 in lumber, 23/32 in panels, 3/4 in particleboard, 1/2 in gypsum, 1/4 in cement millboard, secured batts or tested cellulose.
Searches all 4,276 IRC 2024 sections, 5,532 IBC 2024 sections and defined terms (Chapters 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33 so far) and each city's local rules as they are added. Section numbers and titles from the International Residential Code and International Building Code, 2024 editions, copyrighted by the International Code Council; the IRC's electrical chapters (34 to 43) follow NFPA 70, the National Electrical Code. Requirements are summarized in our words (IRC Chapters 3 to 43, IBC Chapters 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33); read the full text at the link on each result. Local values come from each city's published documents.
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