San Mateo · San Mateo County
A city that wrote down what a lock has to do.
San Mateo has a Building Security Code with its own chapter, its own sections and its own numbers. If you are fitting hardware here it is worth knowing what it says.
Chapter 23.54, in plain terms
San Mateo Municipal Code title 23 carries a Building Security Code at chapter 23.54, brought in by Ordinance 2008-8 and amended as recently as 2024. It has separate sections for houses, for apartment buildings and for everything commercial.
For a house, section 23.54.080 asks for exterior doors and the garage-to-house door to be solid core at a minimum of one and three-eighths inches, with a deadbolt of at least a one inch throw on top of the deadlatch, and one turn of the inside knob has to pull both back together. Strike screws are at least two and a half inches into solid backing, the deadbolt strike plate is at least 16 gauge, and the jamb has to be solid and void free for six inches either side of the strike.
Then the details most people have never heard of. A mail opening is capped at 24 square inches, and if it sits within three feet of a lock it has to stop someone reaching the inside knob. Every main entry door needs a viewer with 180 degrees of vision. Louvered glass windows are prohibited. Sliding patio doors need the vertical play taken out so the panel cannot be lifted off its track with a bar, which is how most of them actually get opened.
San Mateo Municipal Code ch. 23.54, read from the City of San Mateo Law Library.
The sentence that makes San Mateo different
Section 23.54.015(b): "No alterations, additions, or repairs to existing single family dwelling units shall trigger the need for compliance with the provisions of chapter."
Read that next to South San Francisco, eight miles north, where $5,000 of work in twelve months pulls a house into its security chapter. San Mateo deliberately does the opposite. Remodel your own house here and the chapter does not follow you in.
It does follow apartment buildings and commercial buildings. Under 23.54.015(c)(1), every altered, added or repaired portion of an existing building has to comply. So the same work, on the same street, lands differently depending on whether the building holds one family or twelve.
If you own a single house in San Mateo, that is good news for your budget and it is also the reason nobody is going to check your hardware for you. The state deadbolt duty for rentals still applies.
SMMC §23.54.015.
Almost four in ten homes here are in a building of five units or more
The City's own figures put San Mateo at 39,675 housing units, with 24.5 percent built in the 1950s, more than half before 1960 and about 90 percent over twenty years old. By structure: single family 55.6 percent, two to four units 6.2 percent, and 38.1 percent in buildings of five units or more. Tenure is close to even at 52 percent owner and 48 percent renter.
That 38 percent is the highest multifamily share of any city we cover, and it changes what the work looks like. Lobby doors, stairwell doors, garage gates, laundry rooms, mailbox banks and unit doors are the daily material here, not front paths.
Chapter 23.54.070 has opinions about all of it. Shared exterior doors, garage-to-building doors and stairwell doors below the sixth floor need self-locking deadlatches that let you out without a key but need one to come in, with self-closers. Unit doors need a one inch deadbolt with hardened steel inserts. The laundry room has to stay locked and its lock has to open on unit keys. And every complex entrance is supposed to carry an illuminated diagram showing where you are standing and which unit is where, under a vandal resistant cover.
City of San Mateo Housing Element, age and structure tables; California Department of Finance 2010 structure counts; SMMC §23.54.070.
If you are a landlord here, read this before you change a lock
San Mateo adopted a Residential Tenant Protection Program at chapter 10.100 by Ordinance 2025-11. It passed on 1 December 2025, took effect on 31 December 2025, and is written to sunset on 1 January 2030.
- Just cause protection starts at 11 months of lawful occupancy, earlier than the state's 12.
- A no-fault eviction owes one month's rent in relocation regardless of the tenant's income, with half due within 15 calendar days of serving the notice.
- Failure to comply strictly voids the termination notice.
- Tenants get written notice of their rights in English and Spanish.
None of that regulates locks directly. What it does is make a defective notice worthless, and a lock changed on the back of a worthless notice is an illegal lockout under Civil Code 789.3, which carries $100 a day, a $250 floor and the tenant's legal costs.
Our rule has not changed anywhere we work. We will rekey a property for an owner once possession has actually come back, and we will not change a lock on somebody who still lives there. If a sheriff has carried out a writ, show us the paperwork and we will get on with it.
San Mateo Ordinance 2025-11 and SMMC ch. 10.100; California Civil Code §789.3.
Where we go in San Mateo
San Mateo Park, Baywood, Baywood Park and Baywood Knolls, San Mateo Heights, College Heights, Aragon, Hayward Park, Central and the Central Business District, North Central, Sunnybrae, North and South Shoreview, Shoreline and Shoreline Park, Parkside, Fiesta Gardens, San Mateo Village, Laurelwood, Lauriedale, Foothill Terrace, Country Club Heights, all four quarters of Hillsdale, Bay Meadows, Westshore, Los Prados, Edgewater Isle, Bridgepointe and Mariners Island.
The new Hillsdale Caltrain station sits between 28th and 31st Avenues, which is a useful landmark if you are stranded somewhere off El Camino without a street number.
In an emergency, 20 to 30 minutes.
Questions people ask here
I am remodeling. Do I have to bring my locks up to chapter 23.54?
Not on a single family house. Section 23.54.015(b) says alterations, additions and repairs to an existing single family dwelling do not trigger the chapter. On an apartment or a commercial building, the altered portion does.
I am locked out of the lobby, not my apartment.
Common in San Mateo because so much of the housing is in larger buildings. The lobby door belongs to the building and we need the owner or manager to authorize it. Your own door we can do on your identification.
My sliding patio door does not feel secure.
It usually is not. The code asks for the vertical play to be taken out so the panel cannot be lifted off the track, a deadlock with the screws out of reach from outside, and a secondary lock. Most doors we see here have none of the three.
My tenant moved out. Can you rekey today?
Once possession is actually back with you, yes, same day. If there is any dispute about whether they have gone, we need to see the writ. That is not us being difficult, it is Civil Code 789.3.
Need a locksmith in San Mateo now?
A person answers, at any hour, in English or Spanish. If it is not urgent, we will hold a day and a time for you instead.
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