San Mateo County, CA Accessory Structures: Shed & Carport Rules (2026)
Shed permit rules in San Mateo County, CA, also referred to as storage shed, backyard shed, or accessory building regulations, set size limits, setbacks, and when a building permit is required.
Key Facts
- Max floor area
- 1,000 sq ft
- Max rear yard coverage
- 30%
- Min setback from property line
- 3 feet
- Max height
- 19 ft (14 ft West Menlo Park)
- Enforced by
- Planning and Building Director
Summary
In unincorporated San Mateo County, a detached one-story accessory building in a residential district is capped at 30% of the rear yard, 1,000 square feet, and must sit at least 3 feet from the property line.
In any residentially zoned district, a one-story detached accessory building may be constructed if the building coverage does not exceed thirty percent (30%) of the rear yard area, does not exceed 1,000 square feet in floor area, has a plate height that does not exceed then (10) feet, and is not within three (3) feet of a property line. The maximum building height shall be nineteen (19) feet outside West Menlo Park, and fourteen (14) feet in West Menlo Park.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 47).
Full Breakdown
San Mateo County Zoning Regulations § 8.348.020 caps detached one-story accessory buildings, sheds, garages, workshops, in residential districts at 30% of the rear yard, 1,000 square feet of floor area, and a 10-foot plate height, and requires at least 3 feet of clearance from the property line. Overall height is capped at 19 feet countywide, but only 14 feet in West Menlo Park, where roof dormers are banned and the area above the plate is accessible only from inside. Applies only to unincorporated county land; a use permit under Chapter 8.280 can waive these limits for unusual circumstances.
Violations & Fines
Building an oversized or too-close accessory structure without a valid permit is a zoning violation. Enforcement is by the Planning and Building Director under Chapter 1.40 administrative remedies, and any permit issued in conflict with these standards is void.
Frequently Asked Questions
How big can a shed be in unincorporated San Mateo County?
Does this rule apply inside cities like Redwood City or San Mateo?
Sources & Official References
Other rules in San Mateo County
How San Mateo County compares: Shed Permit Requirements by City·California rules heatmap·Compare San Mateo County to another location·View the California accessory structures overview
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