San Mateo Building Permits: A Home Seller’s Guide

Last updated: November 2026. Reviewed by the Cash Home Buyers CA team.

San Mateo requires a permit for any construction, repair, improvement, modification or demolition, with a short list of exemptions. Knowing which work is exempt helps you judge whether a past project is a problem when you sell.

San Mateo permits at a glance

Item	What the City says
Permit rule	Permit required for any construction, repair, improvement, modification or demolition
Plan check consultation	Monday to Friday, 9:30 to 11:30 a.m.
Phone	(650) 522-7172
Online	Online Permit Center (cityofsanmateo.org)
Payment	Credit and debit card fees of 2 to 3% apply

Work the City exempts from a permit

• One-story detached accessory buildings of 120 sq ft or less
• Rear fences up to 7 ft and front fences up to 3 ft
• Retaining walls up to 4 ft
• Decks of 200 sq ft or less and no more than 30 inches above grade, not attached to the dwelling
• Prefabricated pools of 5,000 gallons or less with walls entirely above grade
• Painting and papering
• Window awnings projecting 54 inches or less
• Water tanks of 5,000 gallons or less

Anything outside these exemptions generally needs a permit. Plan check fees are based on project valuation and the permit fee is paid at pickup. The City publishes a comprehensive fee schedule for 2026-27 on its site.

Permits and your sale

California sellers must disclose known unpermitted work on the Transfer Disclosure Statement. Buyers and lenders often ask for permit records on additions, remodels, roofs and electrical work. You can legalize the work, offer a credit, or sell as-is to a cash buyer.

Seller checklist

• List all work since you bought the home.
• Compare each item to the exemption list above.
• Check the Online Permit Center for permit and final inspection records.
• Call (650) 522-7172 about how to legalize any gaps.
• Keep invoices and sign-offs.

Closing costs

San Mateo County’s documentary transfer tax is $0.55 per $500 of sale price, or $660 on a $600,000 sale. Confirm city-level taxes with escrow.

How to sell a house in San Mateo

1. Review your permit history.
2. Decide whether to legalize, credit, or sell as-is.
3. Request a cash offer from us.
4. Pick a closing date, often within days.
5. Close through escrow and get paid.

How to tell whether past work on a San Mateo home needed a permit

Start with what the City itself exempts, because it is a short list: small one-story detached accessory buildings, low fences and retaining walls, small decks that sit close to the ground and are not attached to the house, small prefabricated pools, painting and papering, awnings and small water tanks.

Almost everything else that changes the structure or the building systems generally falls outside that list.

That includes added or enclosed rooms, a converted garage, a relocated kitchen or bathroom, a new electrical panel or added circuits, re-piped plumbing, a new water heater or furnace, and structural changes such as removing a wall.

A practical way to check is to go room by room. For each space ask whether it was built, finished or changed after the original construction, who did the work, and whether you ever saw an inspection sticker or a signed-off permit card.

If you bought the house with the work already in place, the same questions apply: the seller may have disclosed it, but a disclosure is not the same as a permit on file.

Open permits, closed permits and no permit at all

These three situations look similar from the outside but are treated differently by buyers and lenders. A closed (finaled) permit means the work was inspected and approved. An open permit means the permit was pulled but the final inspection never happened, so the work is not signed off.

No permit means the City has no record of the work at all.

The City’s Online Permit Center is where you can look up what is on record for an address, and the plan check line at (650) 522-7172 can explain what it would take to close out or add to the record.

Open permits and missing permits are the ones that tend to surface during a sale, because a buyer’s agent or title and appraisal process may pull the permit history. Knowing your own record before the buyer does gives you time to choose a response instead of reacting to a request.

What buyers, lenders and insurers tend to ask

• Buyers often ask for permits on additions, roofs, electrical and plumbing, and may ask for a price reduction or repair credit when work is not documented.
• Lenders and appraisers may exclude unpermitted square footage from the value, which can leave a financed buyer short.
• Insurers can ask about the age and condition of electrical and plumbing, and unpermitted work can complicate a claim.

None of this makes an unpermitted improvement illegal to sell around. It means the price, the timeline and the type of buyer all depend on how the gap is handled.

Your options when you find a permit gap

1. Legalize it. Ask plan check what documents the City would need and what inspections and corrections would likely follow. This can raise value but takes time and money.
2. Sell with a credit. Disclose the work and negotiate a price reduction instead of fixing it.
3. Remove or restore. In some cases, returning a space to its original permitted state is simpler than legalizing it.
4. Sell as-is for cash. A cash buyer purchases the house with the gap in place and prices the risk into the offer, with no repair requests or inspection contingencies.

Whichever route you choose, California sellers must answer the Transfer Disclosure Statement honestly, including questions about work done without permits.

Preparing for a plan check consultation

Plan check consultation hours are Monday to Friday, 9:30 to 11:30 a.m., and the plan check line is (650) 522-7172. Bring the address, a sketch or photographs of the work, any old permit numbers and a list of specific questions, such as whether a past conversion can be legalized. Write down the answers and the name of the person who gave them.

Fences, sheds and small exempt work

A one-story detached accessory building of 120 square feet or less does not need a permit, and rear fences up to 7 feet and front fences up to 3 feet are exempt. Exempt does not mean free of other rules: setbacks, easements and neighbor issues still apply. If you rely on an exemption, keep the city’s page or an email as evidence.

Roof, water heater and electrical jobs

These are the jobs most often done without a permit and most often asked about by buyers. If you replaced a roof, water heater, furnace or panel, find the permit and the final inspection. If you cannot, ask plan check whether the city has a record and what it would take to document the work now.

Keeping records for the next owner

Save the permit, the inspection sign-off, plans and the contractor’s information with your closing papers. A short folder answers most questions a buyer’s inspector or lender asks. For work with no paperwork, write a factual description of what was done and when, so your disclosure is accurate and consistent.

Frequently asked questions

Do I need a permit for a shed in San Mateo?

Not for a one-story detached accessory building of 120 sq ft or less.

How tall can a fence be without a permit?

Rear fences up to 7 ft and front fences up to 3 ft are exempt.

When can I talk to plan check?

Consultation hours are Monday to Friday, 9:30 to 11:30 a.m.

Can I sell with unpermitted work?

Yes, with disclosure. A cash buyer can purchase as-is.

What does open permit mean when I sell a San Mateo house?

It means a permit was issued but the final inspection was never completed, so the work is not signed off. Buyers and lenders usually want it closed.

Where do I check the permit history for my San Mateo address?

The City’s Online Permit Center is the place to start, and the plan check line at (650) 522-7172 can help if the record is unclear.

How do I check San Mateo permit records?

Use the city’s Online Permit Center to look up what is on record for an address, or call plan check at (650) 522-7172.

What is an open permit in San Mateo?

A permit that was pulled but never received a final inspection, so the work is not signed off.

More guides

• San Mateo code enforcement guide
• San Mateo zoning and ADU guide
• San Mateo County property tax guide

Sources

• City of San Mateo, Building Division

This guide is general information, not legal advice. Confirm current rules with the City of San Mateo.