Multifamily Roof Replacement Title 24 Requirements
When more than half of a multifamily roof, or more than 2,000 square feet if that is smaller, is replaced or recovered, Section 180.2(b)1A adds reflectance and insulation rules by climate zone. A low-sloped roof needs R-14 continuous insulation or U-0.039 in zones 1, 2, 4 and 8 to 16. Roofing products must meet Section 110.8(i).
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The trigger
Any replaced, recovered or recoated multifamily roof must meet Section 110.8(i), which means aged reflectance and emittance values that are certified and labeled, or the code's defaults. The reflectance and insulation items apply once more than 50 percent of the roof, or more than 2,000 square feet, whichever is less, is altered. The manual words the half as 50 percent or more, so confirm a borderline job.
Low-sloped roofs, zone by zone
Low-sloped means a rise to run ratio under 2:12. Two separate tests apply.
- Reflectance: aged solar reflectance 0.63 and thermal emittance 0.75, or SRI 75, in zones 2, 4 and 6 to 15.
- Insulation: R-14 continuous or U-0.039 in zones 1, 2, 4 and 8 to 16.
Zones 3 and 5 therefore meet neither test, zones 6 and 7 only the reflectance test, and zones 1 and 16 only the insulation test. Table 180.2-A trades reflectance for deck insulation: R-2 to R-10 in zones 6 and 7, R-16 to R-24 in the others. Relief covers a recover with new R-10 above the deck, rooftop equipment left in place, and tapered insulation that averages R-14.
Steep-sloped roofs
Zones 4 and 8 to 15 need aged solar reflectance 0.20 and emittance 0.75, or SRI 16. Any one of these is accepted instead: ceiling insulation of R-38 or U-0.025, an attic radiant barrier, no ducts in the attic in zones 2, 4, 9, 10, 12 and 14, or R-2 continuous insulation above or below the deck.
Exemptions and the wrong table
Roof area under building-integrated solar panels, and roofs weighing 25 pounds per square foot or more, skip the reflectance values. Multifamily roofs follow Section 180.2, not the nonresidential Table 141.0-C, which sets different insulation levels; compare the commercial roof replacement route. Attic ceiling insulation is a separate item, triggered when the ceiling insulation is altered or a new duct system goes into a vented attic.
Context sits on multifamily remodels and the roof replacement question; a house follows residential re-roofing rules instead. Reports start at the multi-family service.
Common Title 24 Questions
- Do apartments need Title 24?
- Does a duplex need Title 24?
- Do triplexes and fourplexes need Title 24?
- Which Title 24 forms does a multi-family project use?
- What is an LMCC certificate?
- How much does a multi-family Title 24 report cost?
Frequently Asked Questions
Roofing products must meet Section 110.8(i) for any replacement, recover or recoat. The reflectance and insulation items apply once more than half the roof, or more than 2,000 square feet if that is less, is altered.
A recoat for renewal or maintenance is exempt from the low-sloped insulation requirement. A recoat that is part of a recover counts as a recover.
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