Slab Floor Title 24 Requirements for Additions and Conversions
A slab floor needs perimeter insulation only in climate zone 16, at R-7 or F-0.58, for additions and conversions as well as new homes. Zones 1 to 15 have no requirement unless the slab is heated. The manual does not say whether an already-poured garage slab in zone 16 is excused, so that case goes to the building department.
- Choose your report
- Upload your plans
- Pay securely
- Permit-ready report by email
The same table in every size band
Section 150.1(c)1D and Table 150.1-A set slab perimeter insulation at no requirement in zones 1 to 15 and R-7.0 or F-0.58 in zone 16, to a depth of 16 inches or the footing depth, whichever is less. The manual's Table 9-4 gives additions the identical split at 400 square feet or less, up to 700, and above. A garage turned into living space is newly conditioned space, which the Standards treat as an addition.
New slab or existing slab
An addition that pours a new slab in zone 16 plans its edge insulation like a new home. The tables say nothing about a slab that is already poured and being converted, as in a zone 16 garage. Whether the department excuses it is its call, so raise it before the permit set is drawn.
A heated slab overrides the table
Radiant tubing in the floor brings in Section 110.8(g) in every zone. Vertical insulation runs from the top of the slab down 16 inches or to the frost line, whichever is greater, and may stop at the footing. The value is R-5 in zones 1 to 15 and R-10 in zone 16. The material needs a solid guard and a rigid plate that blocks insects.
What the material must do
Section 150.0(f) limits slab edge insulation to 0.3 percent water absorption and 2.0 perm per inch, and it must be protected from damage and sunlight. In Very High Termite areas, the manual points to the residential code's foam plastic rules.
Who checks it
Slab edge integrity is verified alongside the air barrier under quality insulation installation, which applies prescriptively to additions over 700 square feet and not to smaller ones (Section 150.2(a)1Bv). For the garage-conversion decision see garage conversions, and for a room addition room additions. The wood-floor case is on raised floor insulation, and the inspection on quality insulation installation. Order from residential Title 24 reports.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
Not under Table 150.1-A, unless the slab is heated. Zones 1 to 15 show no requirement for slab perimeter insulation.
From Table 110.8-A, not Table 150.1-A: R-5 in zones 1 to 15 and R-10 in zone 16, with the depth and guard rules in Section 110.8(g).
Explore Floors and Slabs
- Cantilevered Floors and Overhangs: Floor Insulation Under Title 24
- Do I Need a Vapor Barrier in California? Crawl Space, Walls and Attics
- Rim and Band Joist Insulation: Where Title 24 Wants It
View all Floors and Slabs guides → · Windows and Building Envelope · Title 24 guide