San Jose, CA Building Safety: Anti-Mansionization (2026)
Key Facts
- No-permit FAR ceiling
- 0.45
- No-permit height ceiling
- 30 ft / 2 stories
- Administrative tier
- FAR 0.45–0.65 w/ design criteria
- Hearing tier
- FAR >0.65 or criteria unmet
- Zones covered
- R-1, R-2, RM only
Summary
San Jose requires a Single-Family House Permit once a new house or addition exceeds a 0.45 floor area ratio, or is taller than 30 feet or more than two stories, under Municipal Code Chapter 20.100 Part 9.
The issuance of the building permit will result in a single-family house in any residential district with a floor area ratio equal to or less than forty-five hundredths or height equal to or less than thirty feet and/or equal to or less than two stories; or the site is not an historic resource listed on the historic resources inventory pursuant to Chapter 13.48 of Title 13 of this Code, unless allowed pursuant to the provisions of Part 8, Part 9, and Part 9.5 of Chapter 20.30.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 5 Update 3).
Full Breakdown
Chapter 20.100 Part 9 is San Jose's mansionization control for R-1, R-2 and RM lots. Build within a 0.45 floor area ratio (gross floor area divided by lot area, excluding garages and basements) and stay at or under 30 feet and two stories, and no Single-Family House Permit is needed. Cross a 0.45 FAR up to 0.65 and meet added design criteria (no more than 60% second-story-to-first-floor ratio, 10-foot second-story setback, matching roofline and materials) and the Planning Director can approve it administratively. Miss those criteria, exceed 0.65 FAR, or exceed the height/story cap outright, and the project needs a public hearing before the Director or Planning Commission.
Violations & Fines
No building permit for a single-family house or addition can issue until the required Single-Family House Permit is obtained; building past the FAR/height threshold without one risks a stop-work order from the Building Division.
Frequently Asked Questions
Does San Jose regulate oversized 'mansionization' houses?
Can a big addition still be built without a hearing?
Sources & Official References
Other rules in San Jose
California rules heatmap·Compare San Jose to another location·View the California building safety overview
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Anti-Mansionization in Nearby Cities
How other cities in Santa Clara County handle anti-mansionization.