Type I–IV walls over 40 ft above grade plane with a combustible WRB must pass NFPA 285. Exempt if the WRB is the only combustible part and the covering is brick, concrete, stone, terra cotta, stucco or steel per Table 1404.2, or the WRB meets low heat-release limits (ASTM E1354) and flame spread ≤25 / smoke ≤450.
Frame walls get an interior vapor retarder per Tables 1404.3(1)–(4) or a hygrothermal design; climate zone from IECC Chapter 3. Not needed in zones 1–3, basements, below grade, or in zones 4–8 where Table 1404.3(5) exterior insulation is used.
Class I ≤0.1 perm (polyethylene, foil); Class II >0.1–1.0 perm (kraft-faced batts, vapor retarder paint); Class III >1.0–10 perm (latex or enamel paint).
Zones 1–2: Class III only. Zone 3: II or III. Zone 4 (not marine): II, or III per Table 1404.3(3). Marine 4 and 5–8: I, II, or III per Table 1404.3(3). A responsive retarder is allowed anywhere.
Class III allowed with vented cladding over WSP/fiberboard/gypsum (zone 4–5; fiberboard/gypsum only in 6), or continuous insulation over 2×4 / 2×6: zone 4 R-2.5/R-3.75, 5 R-5/R-7.5, 6 R-7.5/R-11.25, 7 R-10/R-15, 8 R-12.5/R-20.
Zone 3 R-2; zones 4–6 R-3 (2×4) / R-5 (2×6); 7 R-5 / R-7.5; 8 R-7.5 / R-10.
Exterior continuous insulation of at least R-4.5 (zone 4), 6.5 (5), 8.5 (6), 11.5 (7), 14 (8), with ≤R-5 inboard and a ≤1 perm layer on the outside of the wall.
Furring and fasteners through continuous insulation are designed for Chapter 16 loads and cladding weight; through foam sheathing use 1404.5.1 to 1404.5.3.
Combustible coverings: max 10% of wall area where fire separation distance is 5 ft or less, and max 40 ft above grade plane (MCM, EIFS, HPL and foam systems excepted). FRT wood: no area limit and up to 60 ft. Wood veneers per 1404.6.
Installation over foam plastic insulating sheathing
Over foam alone, siding needs a wind rating per Table 1404.15.2 (e.g. 115 mph Exposure B with interior gypsum: −35.5 psf). Exempt over structural backing, with a maker's rating, or where the foam is designed for the load.
Direct cladding screws through foam into steel per Table 1404.5.2.1. Example: #10 screw into 43 mil steel at 16 in o.c., 8 in vertical spacing, 11 psf cladding allows 4.00 in foam.
Direct nails through foam into wood (1¼ in penetration) per Table 1404.5.3.1. Example: 0.131 in nail at 16 in o.c., 6 in vertical spacing, 11 psf allows 2.15 in foam.
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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