Before You Build in San Mateo, CA: Permit & Rule Checklist (2026)

Fences up to 7 feet in San Mateo generally do not require a building permit if they comply with zoning regulations. Fences over 7 feet require a building permit and a SPAR Fence Exception planning application.

Shared fence cost and responsibility between neighbors in San Mateo is governed by California Civil Code §841 (Good Neighbor Fence Act). Disputes are civil matters. SMMC Ch. 27.84 governs fence height and location.

San Mateo's fence height limits: front yard 3 ft solid or 4 ft if 75% open; side/rear max 6 ft (7 ft with permit). Fences over 7 ft require a building permit and SPAR exception. Code: SMMC Ch. 27.84.

Retaining walls in San Mateo under 4 feet in height (measured from bottom of footing) are generally exempt from building permits under the California Building Code. Walls over 4 feet require a building permit and may need engineered plans. San Mateo's hillside terrain makes retaining walls common.

Pool barriers in San Mateo must comply with the California Building Code (Title 24 Chapter 31) and the Swimming Pool Safety Act. Barriers must be at least 60 inches high with self-closing, self-latching gates. At least one additional safety feature is required.

New pools in San Mateo require a building permit. Setbacks: 4 ft from property lines (single-family), 5 ft from structures. Prefab above-grade pools under 5,000 gallons are exempt from permit. Anti-entrapment drains required.

Prefabricated above-ground pools with walls entirely above grade and under 5,000 gallons are exempt from building permit requirements in San Mateo. All other pools require permits and must meet safety act fencing requirements.

San Mateo pools must comply with CA H&S §115920: minimum 60-inch (5 ft) barrier, self-closing/self-latching gates, ground clearance under 2 inches, no gaps over 4 inches. Two additional drowning prevention features required.

Swimming pools in San Mateo require building, electrical, and plumbing permits. Plans must verify proper setbacks per the zoning code. Pool barriers must comply with the Swimming Pool Safety Act. The Building Division reviews pool applications at 650-522-7200.

Hot tubs and spas in San Mateo require building and electrical permits. The same barrier and safety feature requirements as swimming pools apply under the Swimming Pool Safety Act. Safety covers meeting ASTM F1346 may substitute for the barrier requirement.

Garage conversions to ADUs are permitted in San Mateo per California ADU law. Building permit required. No replacement parking is required when converting a garage to an ADU under state law.

San Mateo allows ADUs in all residential zones (SMMC Ch. 27.19). One-bedroom ADUs up to 850 sq ft; two-bedroom up to 1,000 sq ft; detached max 16 ft plate/24 ft peak; 4-ft setbacks. ADUs cannot be STRs.

Small accessory structures (sheds) in San Mateo must comply with SMMC zoning setbacks. Sheds under 120 sq ft and under 8 feet average height generally do not require a building permit but must comply with zoning requirements.

Carports in San Mateo require a building permit under Title 23 and must comply with the zoning standards in Title 27. Carports count toward lot coverage calculations. Garage or carport conversions to ADUs are specifically addressed under Chapter 27.19.

Tiny homes in San Mateo are regulated through the ADU provisions of Chapter 27.19 and California Government Code 65852.2. Tiny homes on permanent foundations may qualify as ADUs (up to 1,200 sq ft detached) or JADUs (up to 500 sq ft). Tiny homes on wheels are classified as RVs and cannot serve as permanent housing.

Outdoor wood-burning fire pits are banned on Spare the Air Alert days throughout San Mateo under BAAQMD Regulation 6, Rule 3. With 19–41 annual alert days expected, backyard wood burning is severely restricted.

Open burning is banned in San Mateo under BAAQMD Regulation 5. Wood-burning devices (fireplaces, stoves, fire pits) are prohibited during Spare the Air Alerts under BAAQMD Regulation 6, Rule 3.

Private tree trimming in San Mateo does not require a city permit. Street trees (public right-of-way) require permission from the Parks Division. Trees must not encroach on adjacent properties or utilities without proper trimming.

San Mateo's water is provided by Cal Water (San Mateo District). Water conservation ordinances (SMMC Ch. 23.72) apply to landscaping. Year-round prohibitions include runoff, watering during/after rain, and midday irrigation.

Private tree removal in San Mateo generally does not require a city permit. Street tree removal requires Parks Division approval. Heritage or protected trees may require additional review.