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.
Bearing studs up to 10 ft tall: 2x4 at 24 in under a roof only, 16 in with one floor; 2x6 at 24 in with one floor, 16 in with two. Nonbearing 2x4 studs reach 14 ft.
Utility-grade studs are spaced 16 in or less, carry only a roof, and are no taller than 8 ft in bearing walls or 10 ft in interior partitions.
Tall 2x6 No. 2 studs under a roof with 6 ft or less of tributary length can reach 18 ft at 16 in or 20 ft at 12 in where snow is 25 psf or less and wind 130 mph or less.
The alternate stud table allows exterior bearing studs up to 12 ft in Exposure B with roof live load 20 psf or less and snow 30 psf or less.
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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