Adding a permanent gas or wood-burning firepit to your San Mateo County property is a real construction project subject to several overlapping codes — fire code, plumbing code, mechanical code, and local zoning. Doing it right protects your home, your insurance coverage, and your liability. Here's what the rules actually require.
Permits
Most San Mateo County cities require a permit for any permanent firepit. That includes:
- Any firepit plumbed with gas (always requires a permit)
- Wood-burning firepits with masonry construction
- Firepits with structural seat-wall surrounds
- Firepits attached to a deck or hardscape with permits
Portable propane firepits (the kind you can move) generally don't require a permit, but check your specific city — Hillsborough and Atherton have stricter rules.
Clearance requirements
From the house
- Minimum 10 ft from any combustible structure (wood-burning)
- Minimum 5 ft from any combustible structure (gas, depending on BTU output)
- Greater distances required in WUI (Wildland Urban Interface) zones
From property lines
Most cities require 3–5 ft minimum from property lines for permanent firepits. Some cities (Hillsborough especially) require larger setbacks.
From overhead obstructions
- Minimum 10 ft of vertical clearance (clear sky above)
- No tree branches within the clearance zone
- Pergolas above firepits require non-combustible roofing or significant additional vertical clearance
Gas firepit requirements
Gas firepits must have:
- Manual shutoff valve within sight of the firepit but outside the burn pan
- Buried gas line meeting depth code (typically 12"–18" depending on material)
- Properly sized line for the BTU demand of the burner
- Lava rock or fire glass that is rated for use (not decorative-only material)
- Burner approved by an NRTL (UL, ETL, CSA)
The most common code failure is undersized gas line. A 90,000 BTU burner often needs a 3/4" line — running off a 1/2" branch causes flame starvation.
WUI zone considerations
If your property is in a Wildland Urban Interface zone (significant portions of unincorporated San Mateo County, Portola Valley, parts of Woodside, Hillsborough's western edges), additional rules apply:
- Open-flame wood-burning firepits often prohibited
- Defensible space requirements within 30 ft
- Some HOAs prohibit any open flame
- Fire department review may be required
Air quality district rules
The Bay Area Air Quality Management District (BAAQMD) prohibits wood-burning fires during "Spare the Air" alerts. For wood-burning firepits, you'll need to:
- Check the BAAQMD alert before burning
- Use only seasoned wood (no construction debris, treated wood, etc.)
- Stay below smoke nuisance thresholds
For these reasons, most permanent firepits we install in San Mateo County are gas, not wood-burning.
Insurance considerations
Many homeowner's insurance policies require firepits to be installed per code with a permit closed out. Installing without a permit can void coverage in the event of a fire. Don't skip the permit to "save money" — the savings are illusory.
Typical permitted firepit cost
- Gas firepit with stone surround (round, ~36" dia): $5,000–$12,000
- Gas firepit with curved seat wall and lava rock: $10,000–$22,000
- Custom masonry firepit with built-in seating: $18,000–$45,000
See a recent firepit + outdoor living project in San Mateo or learn more about our firepit construction.
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