Short answer
A Bay Area ADU often costs more than generic national calculators imply because small detached units still need full kitchen, bath, utility, energy, and permit scope.
Bay Area variables
What changes the budget here.
Detached ADUs need full infrastructure
Foundation, utilities, kitchen, bath, HVAC, electrical, and fire details all show up even at modest sizes.
Garage ADUs are not automatic bargains
A weak slab, low ceiling, moisture, or bad utility access can erase the expected savings.
Drawings are leverage
Permit-ready drawings let builders price the same scope instead of guessing creatively.
Cost table
Directional planning ranges.
| Project | Planning range | Notes |
|---|---|---|
| Detached ADU | $250k-$650k+ | Size, finish, utilities, and site access drive spread. |
| Garage conversion ADU | $120k-$300k+ | Existing garage condition is everything. |
| Planning and permits | $12k-$65k+ | Plans, engineering, title 24, plan check, and fees. |
Local estimate
Run the calculator with Bay Area pressure included.
Live calculator
Bay Area planning range
Value first. No email wall, no fake exact quote.
Want a human to sanity-check the range?
Optional. The estimate already did its job. Send it only if you want a Bay Area planning review.
FAQ
Bay Area answers.
Is this a contractor bid?
No. It is a planning estimate that helps you understand the likely budget range before drawings, engineering, city review, and contractor pricing.
Why is the range wide?
Early construction budgets should be ranges because site conditions, structural scope, utility work, finishes, permits, and contractor availability can move the number fast.
Do I need to enter contact information?
No. The estimate appears first. Contact information is only for saving the estimate or asking for a local review.