ADU permit guide for Portola Valley, California
San Mateo County, CaliforniaReviewed August 28, 2026
Planning & Building Department reviews local ADU permits. Use this page to plan the local process and the fee questions to verify before you submit.
Prepared by GetYourPermit editorial teamReport an error
Permit fee planning by size
GetYourPermit research · 3 published reference lines
| ADU size | Researched range |
|---|---|
| 600 sq ft | $9,235 – $14,450 |
| 800 sq ftimpact-fee band | $13,325 – $20,430 |
| 1,000 sq ft | $15,265 – $23,480 |
| 1,200 sq ft | $17,260 – $26,660 |
Getting the permit
- Department
- Planning & Building Department