Mountain View, CA Accessory Structures: ADU Rules (2026)
ADU rules in Mountain View, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Units allowed
- 1 ADU + 1 JADU per single-family lot
- Max size
- 850 sq ft (1BR) / 1,000 sq ft (2+BR)
- Max height
- 28 ft, 1-2 stories
- Side/rear setback
- 4 ft minimum
- Parking
- 1 space, waivable under Sec. 36.12.95
Summary
A single-family lot in Mountain View can add one accessory dwelling unit plus one junior ADU under Sec. 36.12.75(a). Sec. 36.12.80 caps a single-family ADU at 850 square feet (one bedroom or fewer) or 1,000 square feet (two-plus bedrooms), with a 4-foot side and rear setback and a 28-foot height limit.
a.One (1) accessory dwelling unit and one (1) junior accessory dwelling unit per lot with a proposed or existing single-family dwelling subject to the provisions of Government Code Section 65852.2(A). b.One (1) detached, new construction, accessory dwelling unit that does not exceed four (4) foot side- and rear-yard setbacks for a lot with a proposed or existing single-family dwelling... Gross floor area Maximum: Eight hundred fifty (850) square feet for one (1) bedroom or fewer, and one thousand (1,000) square feet for two (2) bedrooms or more... Height limit... For 1- or 2-story structure: Twenty-eight (28) feet maximum, including a basement level.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 34 Update 4).
Full Breakdown
Sec. 2(A). Subsection (b) adds a separate track: a detached, new-construction ADU on a single-family lot that holds to a 4-foot side and rear setback is allowed even where other standards would otherwise block it. Sec. 80's development table sets the core numbers for single-family ADUs: gross floor area tops out at 850 square feet for a studio or one-bedroom unit and 1,000 square feet for two or more bedrooms, and an attached unit can't exceed 50 percent of the primary home's existing floor area.
Height is capped at 28 feet for a one- or two-story structure, including any basement level. Side and rear setbacks are 4 feet minimum, and the unit needs a separate side-hinged entrance under California Residential Code Section R311. Parking runs one space if the unit has a bedroom, none if it doesn't, but Sec. 95's exemptions, including sites within a half-mile of transit, a historic district, or where an existing garage is converted, can eliminate the parking requirement entirely. Short-term rentals under 30 days are separately prohibited for any ADU of 800 square feet or less under Sec. 105. Multi-family properties get their own, less restrictive standards under Sec. 85, including a 1,200-square-foot cap and no parking requirement for a detached unit.
Violations & Fines
Building an ADU that exceeds the size, height or setback standards of Sec. 36.12.80, or renting a small ADU short-term in violation of Sec. 36.12.105, is enforced under the city's general penalty schedule at Sec. 1.7: up to $100 for a first infraction, $200 for a second within a year, and $500 for each further violation, with a fourth violation in one year chargeable as a misdemeanor. Failing to obtain a required building permit is independently a misdemeanor under Sec. 1.7(c).
Frequently Asked Questions
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Sources & Official References
Other rules in Mountain View
How Mountain View compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Mountain View to another location·View the California accessory structures overview
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How other cities in Santa Clara County handle adu rules.