Garage Conversion ADU Title 24 Checklist
A garage conversion ADU is an addition, so the checklist follows Section 150.2(a): wall insulation that depends on whether the siding stays, then ceiling, slab, glazing and doors, then its own heating, ventilation and lighting, then the CF1R-ADD form.
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1. Walls you keep and walls you add
Where existing siding stays, the old garage walls need cavity insulation only: R-15 in 2x4 framing or R-21 in 2x6, with no continuous insulation. New framing, and walls that lose their siding, follow the package value: U-0.048 in most zones, U-0.065 in zones 6 and 7. The infilled garage-door opening is new framing, so draw it as a wall, or as glazing or a door if one goes there.
2. Ceiling, slab and openings
- Ceiling: at 700 square feet or less, a ventilated attic takes R-38 in zones 1, 2, 4 and 8 to 16, or R-30 in zones 3 and 5 to 7.
- Slab: the addition package asks for no perimeter insulation in zones 1 to 15 and R-7 in zone 16.
- Glazing, on the prescriptive path: at 400 square feet or less, total glass is capped at the greater of 75 square feet or 30 percent of floor area in zones 2, 4 and 6 to 15, so 120 square feet in a 400 square foot garage.
- Doors: opaque doors are U-0.20, and a door with 25 percent glass or more counts as a window (exterior doors).
3. Systems the garage never had
- Heating and cooling with its own thermostat. If the garage is attached, the house duct system with a central return cannot be extended into it.
- Whole-dwelling ventilation sized on the unit floor area, because a new dwelling unit that is an addition gets no size exemption, plus bathroom and kitchen exhaust.
- Lighting to Section 150.0(k), with no size exceptions for ADUs.
4. Paperwork
A prescriptive conversion goes on CF1R-ADD-01-E, or CF1R-ADD-02-E when nothing needs field verification. If an ECC-Rater must test something, the CF1R is registered with an ECC-Provider first. Expect no credit for testing the old walls, because existing walls around newly conditioned space count as new. A garage converted earlier without a permit is judged as the building department decides (unpermitted work).
See does a garage conversion need Title 24, the attached ADU report and room addition limits. Our ADU Title 24 reports start from this list.
Common Title 24 Questions
- Do ADUs need Title 24 in California?
- What plans are needed for an ADU Title 24 report?
- How much does an ADU Title 24 report cost?
- How long does an ADU Title 24 report take?
- Does a garage conversion ADU need Title 24?
- Does a JADU need a Title 24 report?
Frequently Asked Questions
No. A garage conversion is an addition, and Exception 6 to Section 150.2(a) removes the photovoltaic requirement for additions.
No. The Energy Commission says existing walls that enclose newly conditioned space are considered new, so ECC verification of existing conditions applies only to altered components.
Not on the prescriptive path. Quality Insulation Installation does not apply to additions of 700 square feet or less, unless the model takes credit for it.
Explore ADU and JADU
- Does a Garage Conversion ADU Need Title 24?
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- Junior ADU (JADU) Title 24 Checklist
- New Detached ADU Title 24 Checklist
- Do Pre-Approved ADU Plans Come With Title 24?
View all ADU and JADU guides → · Permits and Compliance · Title 24 guide