ADU comparisons
Pre-approved plans vs custom ADU plans
By the HyreADU research desk. Last checked .
The short answer
Pre-approved plans vs custom ADU plans is a trade between a faster review and a fitted design.
In California, a complete application for a detached ADU using a plan preapproved in the current code cycle must be decided within 30 days (Gov. Code § 65852.27).
A custom plan gets the normal 60-day decision but fits your lot, views and house.
| Factor | Pre-approved plan | Custom plan |
|---|---|---|
| Decision clock in California | 30 days, detached ADUs only | 60 days (Gov. Code § 66317) |
| Design time | Short: pick and adapt | Full design |
| Site work still reviewed | Yes: foundation, utilities, siting | Yes |
| Fit to an odd lot | Only if a plan fits | Drawn to fit |
| Expiry | Ends with the code cycle | Valid for your permit |
When a pre-approved plan wins
A pre-approved plan wins on a flat lot with room for a standard footprint, when one of your city’s plans suits you. Several cities, including Los Angeles, San José, Oakland and Fresno, list plans on their own sites. See ADU plans for programs with links.
When a custom plan wins
A custom plan wins on a slope, a narrow lot, an attached ADU or a conversion, because the 30-day clock covers detached units only. It also wins when the ADU must match the house. Read ADU designer.
What pre-approval does not remove
Pre-approval covers the building design, not your site. Grading, the foundation for your soil, utility connections and setbacks are still reviewed. Plans approved in an earlier code cycle may have expired. Our pre-approved ADU plans research tracks which catalogs are current, and the plan finder checks fit.
A mistake to avoid
The mistake to avoid is choosing a pre-approved plan that does not fit the lot and then changing it. Large changes can take the plan out of the program and back into normal review, losing the faster clock. Check the footprint against your setbacks and the location of the sewer line first.
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
Are pre-approved ADU plans free?
Some city-owned plans are free; designer-owned plans are bought from the designer. We list no prices.
Can I change a pre-approved plan?
Small changes may be allowed; larger ones can lose the faster review. Ask the city.
Does every California city have a program?
Every local agency had to develop one by January 1, 2025, but some catalogs are empty.
Can I use another city’s plan?
Some cities accept plans preapproved elsewhere in the state. Ask yours.
Sources
- Gov. Code § 65852.27 (preapproved ADU plan programs, AB 1332). Checked September 5, 2026.
- Gov. Code § 66317 (ministerial review, completeness and the 60-day decision). Checked September 5, 2026.
- LADBS, ADU Standard Plan Program. Checked September 5, 2026.
- City of San José, Preapproved ADUs. Checked September 5, 2026.
- City of Oakland, Apply for ADUs with Pre-Approved Plans. Checked September 5, 2026.
- City of Fresno, ADU and Small Homes 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.