Guide
What homeowners need to know.
Legal living space has rules
An ADU garage conversion needs permits, not just flooring and drywall.
Existing condition is everything
Slab, roof, framing, electrical, plumbing, openings, drainage, and fire separation drive the real budget.
California rules still meet city review
State ADU law helps, but cities process permits and inspect the work.
Cost table
Use ranges until scope is real.
| Item | Planning range | Why it moves |
|---|---|---|
| Planning and permit plans | $10k-$35k+ | Depends on existing condition and city requirements. |
| Conversion construction | $120k-$300k+ | Existing structure and utility upgrades drive cost. |
| Heavy upgrade scenario | $300k+ | Possible when structure, drainage, or utilities are difficult. |
Mistakes
Avoid these expensive shortcuts.
- Assuming California ADU friendliness means cheap conversion.
- Ignoring moisture and slab condition.
- Skipping local city review.
FAQ
Fast answers.
Is a California garage conversion ADU worth it?
It can be, especially for family housing or rental income, but only after feasibility confirms the garage can be converted without ugly code or structural surprises.
Sources