California ADU Parking Requirements Explained

What state law says about ADU parking

Government Code Section 66314(d)(10) provides that parking requirements for accessory dwelling units shall not exceed one parking space per accessory dwelling unit or per bedroom, whichever is less, and that these spaces may be provided as tandem parking on a driveway. The same subdivision also requires the city to permit off-street parking in setback areas in locations determined by the local agency or through tandem parking, unless specific findings are made that parking in setback areas or tandem parking is not feasible based upon specific site or regional topographical or fire and life safety conditions.

Government Code Section 66314(d)(11) 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 an accessory dwelling unit, the local agency shall not require that those off-street parking spaces be replaced. The same subdivision applies whether the space is covered or uncovered, and applies whether the space is converted in place or demolished for a new ADU.

Government Code Section 66314(b)(2) is the broader grant: notwithstanding any other provision, a local agency may reduce or eliminate parking requirements for any accessory dwelling unit located within its jurisdiction. The HCD ADU Handbook restates the rule and reminds permitting agencies that the parking cap and the conversion rule apply together, so a code-compliant ADU typically pays no replacement parking.

• Parking requirement is capped at one off-street space per ADU or per bedroom, whichever is less, under Section 66314(d)(10).
• Converted garage, carport, covered parking structure, or uncovered parking space: no replacement parking required under Section 66314(d)(11).
• A local agency may reduce or eliminate parking requirements for any ADU in its jurisdiction under Section 66314(b)(2).
• Tandem parking on a driveway counts as the required parking space under Section 66314(d)(10).

How garage conversions lose parking without a fight

A garage conversion is the most common ADU type in Orange County and Los Angeles County because the structure is already there. Section 66314(d)(11) is the controlling rule: a city shall not require the off-street parking spaces to be replaced when the garage is demolished in conjunction with the ADU or is converted to one. The same rule applies to a carport, a covered parking structure, and an uncovered parking space.

Section 66314(d)(7) sets a four-foot side and rear setback for a new detached ADU that is not converted from an existing structure, and Section 66314(d)(11) reads with that, so a garage that sits two feet from the side property line can become an ADU at two feet without triggering replacement parking. A garage that already exists is also protected from new setback requirements by the same subsection.

In practice, the homeowner reads the rule, sends it to the city with the application, and the city does not impose replacement parking for a code-compliant garage conversion ADU. The HCD ADU Handbook confirms that the parking cap and the conversion rule apply together, so the typical two-car garage conversion is exempt from replacement parking under Section 66314(d)(11).

What the parking cap looks like on a real lot

Section 66314(d)(10) sets the cap at one off-street space per ADU or per bedroom, whichever is less. A one bedroom ADU triggers at most one space. A two bedroom ADU also triggers at most one space under the per bedroom clause, because one space is less than two spaces. The cap does not rise with the size of the ADU, the size of the lot, or the size of the primary residence.

The same subdivision also says the city shall permit tandem parking on a driveway. The city cannot require the ADU space to be a side-by-side configuration, and the city cannot require a separate parking pad off the driveway. Where the lot has a single driveway that already serves the primary residence, the ADU parking space can be a tandem space behind the primary space.

Section 66314(d)(10) subparagraph (B) requires the city to permit off-street parking in setback areas unless the city makes specific findings that parking in setback areas or tandem parking is not feasible based upon specific site or regional topographical or fire and life safety conditions. The findings must be on the record, and a bare statement that setback parking is undesirable is not enough.

What is not allowed when parking is required

Section 66314(d)(10) caps required parking at one off-street parking space per ADU or per bedroom, whichever is less, and that cap applies even when the lot has no existing parking. A city cannot require two spaces for a single ADU. A city cannot count a parking space in the public right-of-way toward the requirement, and a city cannot require guest parking in addition to the one space.

Section 66321(b)(3) reinforces the parking cap at the lot level: front setback, lot coverage, floor area ratio, and minimum lot size may not be used to prohibit an 800 sq ft ADU that meets four-foot side and rear setbacks. The same section gives the homeowner a separate argument when a city tries to deny the ADU on grounds that the lot is too narrow to fit the ADU and one parking space, because the rule prefers the ADU over the parking.

Section 66325 reinforces both parking rules at the article level: Article 2 supersedes any conflicting local ordinance, except that local agencies may adopt less restrictive requirements. A city ordinance that requires two off-street parking spaces per ADU conflicts with Section 66314(d)(10) and is preempted by state law. A city ordinance that requires zero parking is less restrictive and is allowed.

How L Square confirms the parking rule on real California lots

L Square Design & Build walks the property before pricing, measures the driveway and any covered parking, and confirms whether the ADU is a conversion of an existing garage, carport, or covered parking space under Section 66314(d)(11). On a typical garage conversion lot the rule bars replacement parking. On a detached ADU lot the cap is one off-street space per ADU or per bedroom, whichever is less, and Section 66314(d)(10) applies.

For a garage conversion, L Square's site review checks the slab, ceiling height, fire separation from the main house, sewer lateral location, utility route, and parking replacement rules before pricing. For a detached ADU, L Square's site review checks setback, slope, utility capacity, sewer route, and the city's local parking rule to confirm whether the city has chosen to reduce or eliminate parking under Section 66314(b)(2).

For a homeowner comparing ADU cost across California, the right questions for the city are: (1) is this ADU a conversion of an existing garage, carport, covered parking structure, or uncovered parking space, (2) does the city require parking beyond the Section 66314(d)(10) one space cap, and (3) has the city reduced or eliminated parking under Section 66314(b)(2). Those three answers drive the Section 66314 calculation. L Square Design & Build can be reached at (949) 374-7980 to discuss a specific lot in Orange County or Los Angeles County.