ADU design
Garage conversion plans: what the drawings must show
By the HyreADU research desk. Last checked .
The short answer
Garage conversion plans are usually drawn for the specific garage, because each one has its own slab, walls and openings.
Most city preapproval programs cover new detached units, not conversions; Burbank’s program, for example, excludes garage conversions.
A conversion set typically shows the existing and new floor plan, the infilled door opening, energy compliance, and any foundation or framing upgrades.
What a conversion set usually includes
- A site plan showing the garage, property lines and utility routes.
- Existing and proposed floor plans, with the infilled garage door opening.
- Energy compliance forms showing how the walls, slab and roof meet the energy code for a home.
- Structural notes or calculations if the slab, footings or framing are upgraded.
- Window and door schedules, including an emergency escape opening in each sleeping room.
Why preapproved plans rarely fit conversions
The California 30-day clock for preapproved plans covers detached ADUs (Gov. Code § 65852.27), and a plan for a new building cannot describe your existing garage. Some cities offer conversion guides or templates instead. Check your city’s ADU page before paying for drawings.
Rules that help conversions in California
Two state rules make conversions easier. No setback can be required for an existing structure converted to an ADU in the same location and dimensions (Gov. Code § 66314(d)(7)), and the city cannot require replacement parking when a garage is converted (§ 66314(d)(11)). Ideas for the space are on garage conversion ideas.
A mistake to avoid
The mistake to avoid is drawing the plans before anyone has checked the slab and framing. If the engineer later says the slab must be replaced, the drawings change and the plan check starts again. Pay for the inspection first. The garage conversion vs new build tool lists the checks.
What to do next: check your lot with the ADU feasibility checker, read the questions to ask an ADU builder, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.
Get ADU optionsQuestions
Do I need an architect for garage conversion plans?
In California, not for a conventional wood-frame building of up to two stories (Bus. & Prof. Code § 5537). A designer and engineer may still be needed.
Can I keep the garage door?
Sometimes. See garage conversion with a garage door.
Are there plans for a 2-car garage?
See 2-car garage ADU conversion for layouts.
Does a conversion need a new sewer line?
It needs a connection. Whether the existing lateral can be shared depends on the utility and plumbing code.
Sources
- Gov. Code § 65852.27 (preapproved ADU plan programs, AB 1332). Checked September 5, 2026.
- Gov. Code § 66314 (ADU standards: parking, setbacks, sprinklers). Checked September 5, 2026.
- Bus. & Prof. Code § 5537 (plans exempt from architect licensing). Checked October 27, 2026.
- California Energy Commission, 2025 Building Energy Efficiency Standards (Title 24, Part 6). Checked September 5, 2026.
- International Residential Code 2021 (R305 ceiling height, R310 emergency escape). Checked September 5, 2026.
- City of Burbank, Burbank Preapproved ADU Program. Checked September 5, 2026.
HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax, lending or engineering advice.
Rules vary by state and city; California rules are labeled as such. Spotted an error? Tell us through our corrections page. Licensed professionals can also contribute as named sources.