Santa Clara County, CA Building Safety: Anti-Mansionization (2026)
Key Facts
- FAR cap, lots ≤10,000 sq ft
- 0.35
- FAR cap, underlying lots
- 0.25
- Max dwelling height
- 27 feet
- Two-story houses on underlying lots
- design review required
Summary
On unincorporated county lots bordering Los Altos that carry the -n1 combining designator, homes are capped at a 0.35 floor-area ratio on smaller lots and a 27-foot maximum height, to keep new construction in scale with the neighborhood.
To minimize the differences between the development standards of the County and those of the adjoining City of Los Altos, and to encourage residential development that better complements the character of existing development, the following regulations shall apply to residential development in zoning districts that contain the -n1 designator. A.Floor Area...a.Lots of 10,000 square feet (net) or less: a floor area ratio not to exceed 0.35... B.Height of Dwellings. The maximum height of dwellings shall be 27 feet.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 65).
Full Breakdown
Zoning Ordinance Section 3.40.030 creates the -n1 Neighborhood Preservation combining district for unincorporated county parcels adjacent to the City of Los Altos, explicitly to reduce the gap between county and city development standards. Lots of 10,000 net square feet or less are capped at a 0.35 floor area ratio; larger lots get a sliding-scale formula topping out at 5,700 square feet. Dwelling height in the district is capped at 27 feet, below the county's standard 35-foot residential limit. So-called 'underlying lots' that predate a 1998 cutoff face a stricter 0.25 FAR cap and mandatory design review for any two-story house, specifically to control oversized additions and rebuilds.
Violations & Fines
A building permit application exceeding the FAR or height cap is rejected by county Planning and Development; FAR calculations must be verified, stamped, and signed by a licensed architect, civil engineer, or land surveyor on the site plans before permit issuance.
Frequently Asked Questions
Does this FAR cap apply inside the City of Los Altos itself?
Why does the county impose a lower height limit here?
Sources & Official References
Other rules in Santa Clara County
California rules heatmap·Compare Santa Clara County to another location·View the California building safety overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.