Guide
What homeowners need to know.
Preapproved plans are not universal permission
They can reduce review friction, but the project still needs site-specific information and local processing.
Custom plans fit hard lots
Tight yards, slopes, trees, utility constraints, historic context, and garage conversions often need custom thinking.
California law is the floor
State ADU law matters, but cities still administer permits and local objective standards. Check official sources.
Cost table
Use ranges until scope is real.
| Item | Planning range | Why it moves |
|---|---|---|
| Preapproved plan path | Lower planning friction | Still needs site-specific drawings and city process. |
| Custom ADU plans | $15k-$45k+ | Better fit for constrained or high-value sites. |
| Garage conversion plans | $10k-$35k+ | Existing structure review controls complexity. |
Mistakes
Avoid these expensive shortcuts.
- Picking a plan before checking setbacks and utilities.
- Assuming California state rules replace city submittal requirements.
- Using a plan that nobody owns during corrections.
FAQ
Fast answers.
Can I use the same ADU plan in any California city?
Not safely. A plan still needs site-specific adaptation and must satisfy the local permit process.
Sources