San Mateo County runs down the Peninsula from San Francisco to Silicon Valley, with about seven hundred thousand residents, a coastline and the San Andreas fault. The Planning and Building Department is the authority for the unincorporated areas — the coastside, the hills and the bayside pockets — outside its twenty cities.
This guide covers the Planning and Building Department’s unincorporated-area role, Title 24 with county amendments, and the coastal-zone and seismic layers, and where city work goes instead.
This guide covers unincorporated San Mateo County. The county’s twenty cities each run their own permitting.
The first question in San Mateo County is whether the parcel is unincorporated or inside a city. The Planning and Building Department is the authority only for the unincorporated coastside, hills and bayside pockets; work inside a city files with that city. Coastside parcels carry coastal-development review, and seismic design is central along the San Andreas corridor.
What requires a building permit in San Mateo County?
California builds on a single statewide code — the California Building Standards Code, known as Title 24 — adopted on a three-year cycle by the California Building Standards Commission. The 2025 edition took effect on January 1, 2026 and governs statewide. Cities and counties enforce Title 24 and may adopt local amendments, but an amendment must be filed with the state and may only be equal to or more restrictive than the state code, justified by local climatic, geologic or topographic conditions. So the first question in San Mateo County is which authority has jurisdiction — the city on incorporated parcels, the county in unincorporated territory — and what local amendments sit on top of Title 24.
Permit required
- New commercial, multi-family and residential construction, additions and change of occupancy
- Structural alterations, load-bearing changes, foundations, decks and retaining walls
- Electrical work — services, panels, circuits, solar and EV charging — under the California Electrical Code
- Plumbing under the California Plumbing Code, tied to a licensed contractor
- Mechanical and HVAC change-outs, and work affecting the Title 24 energy envelope
- Re-roofing above the exempt scope, pools, signs, and demolition
Often exempt
- Minor repairs and maintenance replacing materials in kind
- Small accessory structures below the local threshold, where zoning allows
- Painting, flooring, cabinetry and other finish work
- Like-for-like fixture or appliance swaps with no alteration to wiring or piping
Local amendments and thresholds differ from one jurisdiction to the next, so an exempt list from a neighbouring city is not reliable — a project waved through in one place needs a full permit set in the next. An exemption from a building permit is never an exemption from zoning, the statewide energy or green-building codes, or an electrical or plumbing permit. Confirm scope with Planning and Building before work starts.
The statewide layers that apply everywhere
Several parts of Title 24 apply on top of the base building code and routinely catch projects owners assume are exempt: the California Energy Code (Part 6), among the strictest in the nation; CALGreen (Part 11), California’s mandatory statewide green-building code; and the accessibility provisions in Chapters 11A and 11B. Seismic design is built into the code statewide, and in fire-prone areas the wildland-urban-interface rules of Chapter 7A and Cal Fire defensible-space requirements add a further layer. In unincorporated San Mateo County, the Planning and Building Department administers Title 24 with county amendments, and coastal-development and seismic review attach to many coastside and hillside parcels.
Who handles permitting in San Mateo County?
The Planning and Building Department handles permitting and inspections for unincorporated San Mateo County; the twenty cities handle their own.
| Detail | Information |
|---|---|
| Authority | County of San Mateo Planning and Building Department |
| Serves | Unincorporated San Mateo County |
| Phone | 650-363-4161 |
| Portal | Online permitting and record search |
| Code | Title 24 with San Mateo County amendments |
| Coastal | Coastal-development review on the coastside |
| Seismic | Central along the San Andreas corridor |
| City work | Handled by the city, not the county |
The Planning and Building Department is the authority for unincorporated San Mateo County, working from its Redwood City office and online systems. Coastside parcels add coastal-development review, and hillside and fault-corridor parcels turn on seismic and grading design.
Confirm the jurisdiction from the parcel first; a project inside a San Mateo County city files with that city’s department under its own code and counter.
Permit types
Residential permits
Unincorporated residential work is permitted and inspected by the county under Title 24 and county amendments. Additions, decks, pools, solar and EV chargers need permits, coastside parcels carry added review, and hillside parcels carry grading and seismic design. A CSLB-licensed contractor pulls the trade permits.
How California contractor credentials work
California licenses contractors statewide through the Contractors State License Board, not locally. The CSLB issues three license types — Class A for general engineering, Class B for general building, and the Class C specialty classifications for individual trades — and a contractor must hold the classification that matches the work. A license is required for any project valued at one thousand dollars or more in combined labour and materials, and, in practice, for any work that requires a permit regardless of value.
In California the license lives with the state, not the city. The same CSLB license is recognised in every jurisdiction, so there is no separate local contractor registration to secure before pulling a permit. What the permitting authority does check is that the license number is active and carries the right classification for the scope, along with workers’ compensation coverage. Confirm the classification matches before filing.
Commercial permits
Commercial and multi-family work in unincorporated areas goes through county plan check against the California Building Code, the Energy Code and CALGreen. It requires CSLB-licensed contractors, stamped drawings with seismic design, and coastal-development review where the parcel sits in the coastal zone.
Licenses, trade classifications and design professionals
Practically, three credential layers appear on California projects: a CSLB license in the correct classification for the contractor pulling the permit; the specialty C-classifications for the electrical, plumbing and mechanical trades; and, on commercial and larger residential work, drawings stamped by a California-licensed architect or engineer. Confirm what Planning and Building requires for the specific building before filing.
San Mateo County permit costs and fees
Budget the county building permit and plan-check fees, separate trade permits, the state Building Standards and seismic surcharges, and coastal or hillside review where it applies. The county publishes a valuation-based schedule; confirm it for your filing date.
| Fee component | How it works |
|---|---|
| Building permit | Based on project valuation or square footage; set by the local schedule |
| Plan check | A percentage of the permit fee or a flat charge, at submittal |
| Trade permits | Separate electrical, plumbing and mechanical fees |
| State surcharges | Building Standards and seismic (SMIP) fees collected with the permit |
| Impact and school fees | Development impact and school-district fees in growth areas |
| Re-inspections and revisions | Additional fees for failed inspections, revisions and expired permits |
California layers two uniform state surcharges — the Building Standards Administration fee and the Strong Motion Instrumentation seismic fee — on top of the local charges, so they appear on permits everywhere. The building and plan-check fees themselves are local and change, and California law limits them to the reasonable cost of providing the service, so a figure from a neighbouring city is not reliable — ask Planning and Building for the schedule in force on your filing date.
Need a real number for a specific San Mateo County project? Send us the scope, address and valuation and we will identify the authority having jurisdiction, the code edition in force and the fee categories that will apply.
Trade permits and who may pull them
Trade permits are separate from the building permit and, on projects that require one, generally cannot be issued until the building permit is in place. Each trade follows its own part of Title 24 — the California Electrical, Plumbing and Mechanical Codes — and is tied to a contractor holding the matching CSLB specialty classification, the same license statewide.
California runs the trades on one statewide license. Electrical work is tied to a C-10 contractor, plumbing to a C-36, and heating and air to a C-20, each licensed by the CSLB rather than the city, so the credential travels with the contractor from one jurisdiction to the next. What changes locally is the permit itself and any local amendments — confirm both with the authority that issues it.
- Electrical work follows the California Electrical Code and a C-10 electrical contractor.
- Plumbing work follows the California Plumbing Code and a C-36 plumbing contractor.
- Mechanical work follows the California Mechanical and Energy codes and a C-20 HVAC contractor.
Permit required
- Service installations, panel upgrades, new circuits, solar PV and EV chargers
- New plumbing, repipes, water heater change-outs, fixtures, backflow and gas piping
- HVAC installation and change-out, ductwork, venting and commercial kitchen exhaust
- Sprinkler, standpipe and fire alarm work on commercial and multi-family structures
Typically exempt
- Replacing a fixture, switch, receptacle or light with no alteration to wiring or piping
- Clearing a stoppage without replacing or rearranging concealed piping
- Filter, thermostat and routine component service
- Like-for-like appliance repair that does not alter the connection
How to apply for a San Mateo County building permit
Only unincorporated parcels file with the county; the twenty cities run their own.
Unincorporated applications run through the county’s online and Redwood City systems.
California licenses contractors statewide; match the classification to the scope.
Coastside parcels add coastal-development review; fault-corridor parcels turn on seismic design.
File the plan set and pay the review fees the county posts.
Issue the permit and request inspections through the county.
Review, corrections and what actually causes delay
In California, the first cause of delay is uncertainty over jurisdiction — filing with the county when a city should have it, or missing a local amendment on top of Title 24. After that come Title 24 energy and CALGreen documentation, a CSLB classification that does not match the scope, and, in fire or coastal areas, defensible-space or coastal-zone requirements that were not addressed up front. Build the plan-check time into the schedule and confirm the checklist with Planning and Building before filing.
Approvals do not stay live indefinitely. A California building permit carries a validity period and can expire if work does not start or stalls between inspections. On phased or financed work, keep the permit active with periodic progress inspections and confirm the expiry window before it passes.
Inspections in San Mateo County
Where a permit is required, standard checkpoints include footing and foundation, framing, rough-in electrical, plumbing and mechanical, insulation and Title 24 energy, CALGreen measures, fire systems on commercial work, and final, with a certificate of occupancy before use. On issuance the county assigns the field inspector and the construction stages that must be inspected.
California inspections are keyed to the code editions in force when the permit issued, so the approved plans and any energy and green-building documentation need to be on site for the inspector to check against. Confirm the notice Planning and Building needs and schedule around its inspection windows.
Do not cover work before the required inspection has been approved. Keep the issued permit, the approved plans, product listings, Title 24 energy documentation and your correction responses available on site.
San Mateo County permit search and official resources
Permit records in California sit with the local authority that issued them. Where the County of San Mateo Planning and Building Department is the authority for unincorporated San Mateo County, it holds the building permit, the inspection history and the certificate of occupancy. If you are buying, refinancing or renovating, confirm that past work was permitted rather than assuming it was — and confirm the code edition that was in force.
Confirm the authority having jurisdiction and the local amendments first. California enforces one statewide code, Title 24, but each city and county adds its own amendments and fee schedule, so the requirements that apply vary by parcel. Confirm current requirements, fees and review turnaround for your filing date.
These are the primary sources behind this guide. Codes, fee schedules and procedures change — confirm the position for your filing date.
- County of San Mateo Planning and Building
- California Building Standards Commission (Title 24)
- Contractors State License Board (CSLB)
- California Coastal Commission
- California Department of Housing and Community Development
Frequently asked questions
Who issues building permits in unincorporated San Mateo County?
The Planning and Building Department issues permits for unincorporated areas such as the coastside and hills; the county’s twenty cities run their own departments.
Does my project need coastal review?
Coastside parcels commonly do; a coastal-development permit can be required on top of the building permit, so confirm before you file.
How does seismic design affect my project?
Seismic design is central along the San Andreas corridor; expect it to shape foundations, framing and connections on most projects.
Do I need a local contractor registration?
No. California licenses contractors statewide through the CSLB; the license must be active and carry the right classification.
How do I know if my parcel is unincorporated?
Confirm with the Planning and Building Department or the county mapping tools; coastside and hill parcels outside the cities file with the county.
How do I run a San Mateo County permit search?
The Planning and Building Department holds unincorporated permit and inspection records; city records sit with each city’s department.
Simplify San Mateo County permitting with Alliance Permitting
Unincorporated San Mateo County turns on jurisdiction, coastal review and seismic design. Clearing those before filing is most of the battle from the coastside to the fault corridor.
Trusted by leading builders, developers, and national contractors — 22 years of filing in the jurisdictions we write about.
Contractors and builders choose Alliance for San Mateo County because the work is done by people who have stood at the counter:
- We confirm whether the parcel is unincorporated or inside a city.
- We manage the county application end to end.
- We confirm the CSLB classification matches the scope.
- We clear coastal-zone and seismic review before filing.
- We submit complete plan sets and track issuance and inspections.
Alliance Permitting is a permit documentation and submission company. We prepare your paperwork, file it correctly and coordinate with the permitting authority through issuance. We are not a contractor and we do not perform licensed plan review or inspections; that work stays with your licensed team and the jurisdiction.
Ready to break ground in San Mateo County sooner?
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More California permitting guides
This guide is provided by Alliance Permitting for general information about San Mateo County permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.