Home Additions in Los Altos Hills, CA
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Site Development Review
Site development review applies to any exterior change, expansion or new coverage, and a site development permit must be issued before the building permit. The path starts with a pre-application meeting and a site analysis meeting. Projects are approved by staff (about 2 weeks), staff with notice at a Site Development hearing (500-foot notice), Fast Track before the Planning Director, or the Planning Commission (6 to 8 weeks, then City Council consent; appeals within 22 days).
Story poles (rules updated September 18, 2025) are required for new buildings, second-story additions, additions over 900 sq ft or raising the roof, and accessory buildings over 900 sq ft. They go up 10 days before the hearing with orange fencing; homes up to 19 feet and 4,000 sq ft may use a 3D rendering instead.
Addition Work
How Much Can You Add?
Floor and development area: maximum floor area (MFA) and maximum development area (MDA) come from a lot-unit-factor formula based on net acreage and average slope. Basements are exempt, garages count, and space over 17 feet tall counts double. Patios, decks, pools, paving and the first 100 feet of driveway count toward development area. Minimum lots are one acre.
- Pathways: a new home, or additions of 900 sq ft or more within 10 years, on a lot shown on the Master Path Plan requires a pathway easement or in-lieu fee.
- Heritage oaks: 36 inches or more in circumference at 4 feet.
- Geology: a geotechnical report reviewed by the Town Geologist, with drainage and erosion review by the City Engineer.
- Before final: screening landscaping with a maintenance deposit, and certified height and location.
26379 Fremont Road, Los Altos Hills, CA 94022 · (650) 941-7222 · Bu******@**************CA.Gov
The Town issues permits and performs inspections through its eTRAKiT Community Development Web Portal.
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Los Altos Hills Home Additions FAQ
Do additions need story poles in Los Altos Hills?
Second-story additions and additions over 900 sq ft or raising the roof do.
How is the maximum floor area calculated?
By a lot-unit-factor formula based on net acreage and average slope.
Do basements count toward floor area?
No. Basements are exempt.
What is the pathway requirement?
Additions of 900 sq ft or more on Master Path Plan lots require an easement or in-lieu fee.