Home Additions in Belmont, CA
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Which Review Tier Applies?
Belmont Single Family Design Review has three tiers:
- Tier 1 (staff): ground-floor additions up to 399 sq ft with plate height of 12 feet or less and roof height of 18 feet or less, and additions that do not enlarge the footprint. No neighbor outreach.
- Tier 2 (Zoning Administrator): ground-floor additions of 400 to 899 sq ft, upper-floor additions up to 399 sq ft, or combined additions up to 899 sq ft. Outreach and notice within 150 feet; a hearing only if requested.
- Tier 3 (Planning Commission): new homes, upper-floor additions of 400 sq ft or more, combined additions of 900 sq ft or more, or grading over 500 cubic yards or 6,000 sq ft of disturbance. Outreach within 300 feet and a public hearing.
Tier 2 and 3 projects start with a pre-application meeting, and appeals are due within 10 days. A licensed architect is required on slopes of 18% or more.
Addition Work
Hillsides, Trees and Improvements
Hillside lots: the San Juan Hills and Western Hills Area Plans govern hillside lots, which can involve steep slopes, geologic hazards, access improvements and lot-legality questions. Grading over 50 cubic yards, more than 2 feet of cut or fill, or over 2,000 sq ft disturbed triggers grading and geologic review.
Protected trees: coast live oak, valley oak, redwood, madrone, bay laurel and buckeye at 10 inches in diameter, and any tree at 14 inches on a single trunk or 18 inches combined on multi-stem trees.
- Additions over 25% of existing floor area can trigger public improvements.
- School fees go to Sequoia Union High School District and the Belmont-Redwood Shores School District for projects over 500 sq ft.
Fire and sprinklers: San Mateo Consolidated Fire serves Belmont. Its standard requires a sprinkler retrofit when work covers more than 50% of the existing floor area, and detached ADUs are exempt unless the main house is sprinklered.
City Hall, One Twin Pines Lane, Suite 110, Belmont, CA 94002 · (650) 595-7422, pe**********@*****nt.gov
Walk-in hours Monday, Wednesday and Thursday, 8:30 to 11:30 a.m., with Building, Planning and Engineering staff; appointments at other times. Permits and inspections run through eTRAKiT, with morning (9 to noon) and afternoon (1 to 4) inspection windows.
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Other Belmont services: ADUs · Bathrooms · Kitchens · New Homes · Belmont overview
Same service nearby: San Carlos · San Mateo · Hillsborough
Belmont Home Additions FAQ
Does a small addition need a hearing in Belmont?
Ground-floor additions up to 399 sq ft are approved by staff (Tier 1).
When does an addition go to the Planning Commission?
Upper-floor additions of 400 sq ft or more, or combined additions of 900 sq ft or more (Tier 3).
Is an architect required?
On slopes of 18% or more.
Are neighbors notified?
Tier 2 within 150 feet; Tier 3 within 300 feet.