San Mateo Code Enforcement Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

In San Mateo, code enforcement is usually complaint driven, voluntary correction is often the first step, and fines or penalties can follow if a problem is not fixed. This guide explains how the City of San Mateo handles reports, what the city says about home occupations, fences and signs, and what an open violation means if you want to sell. It covers the city, not unincorporated San Mateo County.

San Mateo code enforcement at a glance

Report a problem	My San Mateo Online Service Request Portal, or (650) 522-7150
Spanish line	(650) 522-7166
Planning Division	(650) 522-7212
Finance (business license)	(650) 522-7100
How cases start	Complaint, staff observation, or permit and variance actions
Typical first step	Voluntary correction, then fines or penalties

How a case begins

The city’s FAQ says an enforcement case can begin three ways: a complaint, a staff observation, or a permit or variance action. Residents can report a concern through the My San Mateo Online Service Request Portal or by calling (650) 522-7150, with a Spanish-language line at (650) 522-7166.

The city says complaints need the caller’s name and contact number, which it keeps confidential, and that complaints without that information will not be assigned for investigation.

What happens after a report

San Mateo’s approach emphasizes voluntary compliance. Staff typically contact the owner, explain what the code requires and give time to correct the problem. If the owner does not fix it, the city can move to fines and penalties.

If you receive a notice, respond in writing, note the correction deadline and keep records of the work you do. Because permit actions can themselves trigger a case, a project started without a permit may surface when a neighbor reports it or when you later apply for another permit.

Common issues the city addresses

Home occupations

San Mateo allows home-based businesses under the rules in Section 27.16.040 of its municipal code.

The city’s FAQ summarizes the limits: the business can use no more than 400 square feet or 20 percent of the home, whichever is less, hours are limited to 8 a.m. to 6 p.m., and no more than five client visits per day are allowed.

A business license is handled through Finance at (650) 522-7100, and Planning at (650) 522-7212 can confirm whether your use qualifies.

Fences, hedges and signs

The city regulates fence and hedge height and the placement and size of signs. Rules vary by zone and location on the lot, especially near corners and the street, so check with Planning before you build or post anything.

Unpermitted construction and units

Garage conversions, added rooms and backyard units without permits are among the most common reasons a property is flagged. Our San Mateo zoning and ADU guide explains which units the city allows to be built through a ministerial building permit, which helps owners judge whether a past project could be legalized.

If you are served with a notice

• Read the notice for the specific code section and the correction deadline.
• Call the number on the notice and ask what proof of correction the city wants.
• Fix what you can quickly and photograph the before and after.
• Ask in writing for a re-inspection once the work is complete.
• If the issue involves construction without a permit, ask Planning and the Building Division whether the work can be legalized and what plans and fees it would require.
• Request the city’s written confirmation when a case is closed.

Open violations and selling your San Mateo house

California sellers generally must disclose known violations and unpermitted work, and title companies can flag recorded liens. Buyers who finance their purchase often want violations resolved before closing, which can slow a traditional sale. Our statewide guide to selling as-is with unpermitted work covers disclosure in detail, and the seller closing costs guide explains what to budget for.

Owners in this position usually weigh three paths: correct the violation and close the case before listing, disclose it and accept a lower price on the open market, or sell as-is to a cash buyer who takes the property in its current condition. Cash buyers do not need the city’s sign-off before closing, but any fines owed are generally settled from proceeds.

Inherited and tenant-occupied properties

Heirs and landlords often receive notices for problems they did not create. If you inherited a property, see the probate home sale guide and the inherited home tax basis guide for the sale and tax side of the process. Tenant-occupied homes can be sold with tenants in place.

How to sell a house in San Mateo

1. Gather notices, correspondence and any permit records.
2. Check title for any recorded liens.
3. Request a no-obligation cash offer for the house as it stands.
4. Choose a closing date.
5. Close with no repairs, showings or city sign-off required from you.

Related local pages: sell as-is in San Mateo, sell fast, cash home buyers and the cash offer process.

Frequently asked questions

How do I report a code violation in San Mateo?

Use the My San Mateo Online Service Request Portal or call (650) 522-7150. Spanish speakers can call (650) 522-7166.

Are anonymous complaints investigated?

The city says complaints need a name and contact number, which are kept confidential, or they will not be assigned.

What are the home occupation limits?

The city summarizes them as 400 square feet or 20 percent of the home, hours from 8 a.m. to 6 p.m., and up to five client visits a day.

How does a case start?

Through a complaint, a staff observation, or a permit or variance action.

What happens if I do not fix a violation?

The city generally seeks voluntary correction first, then may pursue fines and penalties.

Can I sell a San Mateo house with a code violation?

Yes. You can disclose it and sell as-is, including to a cash buyer.

More guides

• We Buy Houses in San Mateo
• We Buy Houses in San Mateo County
• San Mateo County Property Tax Guide
• San Mateo Zoning and ADU Guide
• San Mateo County Deed Transfer Guide
• All California Guides

Sources

• City of San Mateo: Code Enforcement FAQ
• City of San Mateo: Planning Division

This guide is general information from public sources, not legal advice. Confirm current rules with the city.