No. When a garage, carport or parking space is demolished or converted as part of building an ADU, California law says a city cannot require those off-street spaces to be replaced. There is no exception written into it, and in San Mateo the rules go further still: no parking is required for any ADU at all, and you get to keep the driveway.
This is the question we are asked more than any other, and it is the one competitors are vaguest about. So here is the actual position, with the statute.
What the law actually says about replacing parking
The relevant text is short and unusually direct. Government Code section 66314 provides that when a garage, carport, covered parking structure or uncovered parking space is demolished in conjunction with the construction of an accessory dwelling unit, or converted to one, the local agency shall not require that those off-street parking spaces be replaced [Source: California Legislative Information 2026].
Two things worth noticing. It covers both demolition and conversion, so you are protected whether you reuse the structure or knock it down and build in its place. And it carries no carve-out for lot size, neighborhood, or how much street parking exists nearby.
One more provision compounds it. The same chapter bars a city from imposing any parking standard at all where the ADU is part of the existing primary residence or an accessory structure. A converted garage is an accessory structure, so the new unit does not need parking of its own either.
What San Mateo adds on top
The city goes further than the state floor. San Mateo Municipal Code chapter 27.19 states plainly that no off-street parking shall be required for any ADU or JADU, full stop, without reference to whether a garage was involved [Source: City of San Mateo Municipal Code 2026].
The detail owners appreciate most is the next one. When a garage is converted or demolished for an ADU, the existing driveway and curb cut do not have to be removed and may be kept as parking area. So in practice you lose the covered space and keep the paved one. Most households find that is the trade they were willing to make anyway.
Rules differ across the Peninsula, and a handful of cities are less generous than San Mateo on the margins. The statutory protection above applies everywhere in California regardless.
Why so many builders still hedge on this
Because the law changed, repeatedly, and a lot of published guidance has not caught up. California's ADU statutes were renumbered twice in two years, moving out of section 65852.2 and into the 66310 series, then renumbering again in January 2026 [Source: California Legislative Information 2026]. Guidance written against the old numbering is still downloadable, still ranks, and still says things that are no longer true.
San Mateo's own older ADU handout is a good example. The 2021 version required one parking space per ADU and is still a live download, though the city no longer links to it. If a contractor quotes you a parking requirement, ask which code section they are reading it from and check the date.
Where parking does still come up
Three situations, none of which is a replacement-parking requirement:
- Your own preference. San Mateo permits voluntary parking, up to two stalls per unit, and allows a wider driveway for a converted single-car garage. You can add parking; you cannot be made to.
- Fire access. Driveway width and access are a fire code matter rather than a parking one, and on long or constrained driveways it can shape the design.
- An HOA. Private covenants are a separate question from city zoning. If your property carries recorded CC&Rs, read them.
What none of these is: a requirement to rebuild the space you gave up. Cost and feasibility on a conversion are driven by site conditions and the existing structure, not by parking.
So should you convert the garage?
Parking is rarely the thing that decides it, which is the point of this article. The real constraints are ceiling height, the condition and slope of the slab, and whether your electrical service has capacity. We set all three out on our garage conversion page, including the code minimums and what usually goes wrong.
One more thing worth putting in the same column as the parking you keep. An ADU of 750 square feet or less pays no impact fees at all, and above that the fees are charged only in proportion to the unit's size against your main house [Source: California Legislative Information 2026]. A typical single-car garage sits comfortably under that threshold, so a conversion frequently avoids a five-figure charge that a larger new build would carry. It is worth designing to the threshold deliberately rather than crossing it by thirty square feet.
The honest summary: a conversion is the lowest-cost route to real square footage because the shell exists, it carries no setback requirement, and it does not trigger the solar requirement that a newly built detached ADU does. What you give up is the garage. What you do not give up is the parking, because the driveway stays.
Frequently asked questions
Does this apply if I demolish the garage rather than convert it?
Yes. The statute covers a garage that is demolished in conjunction with constructing an ADU as well as one converted into it. That matters more than it sounds, because a garage with inadequate headroom or a failing slab is sometimes better replaced than reused. You are not penalized with a parking requirement for choosing the sounder construction route. The related setback protection works similarly: you may rebuild in the same location and to the same dimensions and keep the existing setback.
Can the city make me add parking for the new unit?
Not where the ADU is created within the existing home or an accessory structure such as a garage. State law bars a parking standard in that situation outright. San Mateo goes further and requires no parking for any ADU or junior ADU regardless of type. Other Peninsula cities cap it at one space per unit or per bedroom with a long list of exemptions, several of which are easy to meet, including being within half a mile of transit or building a studio with no separate bedroom.
Do I have to remove the driveway and curb cut?
Not in San Mateo. The code expressly says the existing driveway and curb cut are not required to be removed and may be maintained as parking area. That means the practical outcome of a garage conversion is usually that you keep somewhere to park a car, just without a roof over it. Confirm the position locally if you are outside the city, since this particular allowance is a local provision rather than a state one.
What about the garage door opening, can I just leave it?
No, it has to be closed and framed as a wall, and there is a local detail worth knowing. San Mateo amended the residential code so that in our seismic design category, gypsum board is not permitted as intermittent braced wall panels. The new wall where the door was needs wood structural panel bracing rather than drywall, tied to a foundation at that location. It is ordinary work for a licensed builder and a common cause of correction notices when it is not detailed properly.
Getting a real answer for your property
Parking is the easy part. Whether your garage is worth converting comes down to headroom, the slab and your service capacity, and those take a site visit rather than an article.
Book a free consultation and we will look at all three and tell you honestly whether a conversion or a detached unit is the better use of your money. No obligation, and we respond within one business day. You can also read how the three ADU types compare, see what we have built, or browse our FAQs.