Compare cities · Santa Clara County
In an interim: HCD found the city's 2024 ADU ordinance non-compliant and the city says it applies state law directly until a new ordinance lands, targeted for end of 2026. The 800 sq ft and 16 ft figures on older handouts are not the binding limits; state minimums are.
Detached, new-construction plans pre-approved for local building, fire and Reach Code compliance, published on the city's ADU Accelerator gallery. Under state law a detached unit built from a pre-approved plan gets a 30-day decision instead of 60.
Program page →Legalise an unpermitted unit built or converted before 2020 with no enforcement action, penalties or violation fees, and expedited building review.
State law sets a floor no ordinance can go under. The full guide, with every statute cited →
Every lot zoned for residential use may have at least one ADU, and a single-family lot may also add a JADU. A city cannot say no to the category.
A detached or attached unit of up to 800 sq ft, 16 ft tall, with 4 ft side and rear setbacks must be approved regardless of local lot-coverage or floor-area limits.
A city cannot require more than four feet from side and rear lot lines for an ADU.
Once your application is complete the city has 60 days to approve or deny; 30 if you build from a pre-approved plan.
Convert or demolish a garage to build an ADU and the spaces you lose never have to be replaced.
Prohibited entirely below 750 square feet, and proportional above it.
Reviewed against an objective checklist. No design review board, no hearing, no discretion about whether they like it.
A city cannot require you to live on the property for a standard ADU. A JADU is different: since 1 January 2026 owner occupancy is required when the JADU shares sanitation with the main house.
Mountain View is inside our service area, and ADUs are all we do. We bring in the architect and engineer or work with yours, run the permit with Mountain View, and build with our own crew: about 6 weeks of construction for a detached unit once the permit is in hand.
What we can't tell you from here is what your particular lot will take: setbacks, the sewer lateral, the panel, grade and access. That is what the free site walk is for.
Tell us about your lot and what you're hoping to build. We'll reach out to set a time to walk it with you. No obligation.
Thanks. We've got your details and sent a confirmation to …. Sam or Brad will reach out shortly to set a time for the walk.