What you can build

Converting a garage into an ADU or living space

Checked against state laws and official agency sources · Last reviewed October 9, 2026

Do you need a permit to convert a garage?

Yes. Federal Way, Washington, puts it plainly: "Converting a residential garage into living space requires a building permit, and may require electrical, mechanical, and plumbing permits as well." The new living space "will need to comply with current building and energy code requirements."

If the garage will become a separate home (an ADU), it must also meet your city's ADU rules. Seattle says ADUs "are not legal unless they have been established through a permit process." See the ADU permit process for the steps. [1][5]

What state ADU laws say about garages

In California, state law allows ADUs inside attached garages, inside detached garages, and as new units that replace a detached garage:

• No new setbacks. No setback may be required for an ADU created inside an existing structure, or for a new structure built in the same spot and to the same size as the old one.
• Room to add stairs or an entry. An ADU converted from an accessory structure, such as a detached garage, may grow by up to 150 square feet only to provide a way in and out, such as a staircase.
• No size cap on conversions. Unit size limits don't apply to converting existing space. The height of a conversion is limited to that of the original structure.
• Demolition reviewed together. If you tear down a detached garage to replace it with an ADU, the city must review the demolition permit at the same time as the ADU. It can't require you to post a notice of the demolition unless the property is in an architecturally and historically significant district.
• Junior ADUs. An attached garage counts as part of the house, so it can become a junior ADU of up to 500 square feet.

In Washington, covered cities "must allow accessory dwelling units to be converted from existing structures, including but not limited to detached garages, even if they violate current code requirements for setbacks or lot coverage." [3][4]

Do you have to replace the lost parking?

In California, no. When a garage, carport, covered parking structure or uncovered parking space is torn down to build an ADU, or converted to an ADU, the city "shall not require that those off-street parking spaces for the primary unit be replaced." Cities also can't require parking for an ADU that is part of the main home or an existing accessory structure. They can't require parking for a junior ADU, "even when the JADU is converted from an attached garage."

Other states limit parking rules too:

• Arizona and Montana: cities may not require added parking for an ADU.
• Colorado: covered cities generally may not require a new off-street parking space when you build or convert an ADU, with limited exceptions.
• Massachusetts: no more than one added space, and none within half a mile of certain transit stations.
• Washington: no off-street parking may be required within half a mile walking distance of a major transit stop, and other limits apply elsewhere.

These state laws are about the ADU. If you convert a garage into a family room instead of an ADU, ask your city whether its parking rules for the main home still apply. [3][4][6][7][8][9]

Building code issues to plan for

These examples come from two city handouts. Los Angeles's ADU bulletin (revised August 2026) applies California's 2025 Residential Code as Los Angeles amends it. Federal Way, Washington's garage conversion checklist is from 2022. Your city's rules may differ, so confirm with your building department.

• Foundation and slab. In Los Angeles, existing foundations may stay if they are in good condition and met code when built. Existing slabs may stay "with an approved sealant as a moisture barrier."
• The garage door opening. Los Angeles lets the garage door header stay. The opening is filled with a framed wall of 2x4 studs at most 16 inches apart. Federal Way says the garage door must be replaced with a framed wall that can hold the required insulation.
• Entry door and escape windows. In Los Angeles, the main entry door must be side-hinged and at least 3 feet wide by 6 feet 8 inches tall. Every sleeping room needs an emergency escape opening to a yard or public way. It must be at least 24 inches high, 20 inches wide and 5.7 square feet open, with the bottom no more than 44 inches above the floor.
• Ceiling height and room size. Los Angeles requires a ceiling height of at least 7 feet throughout. Habitable rooms must be at least 70 square feet and at least 7 feet in any direction.
• Insulation and energy. Federal Way says a previously unheated space "shall fully comply with the current energy code requirements for attic, wall, and floor insulation," plus compliant windows and doors. Los Angeles requires new work to meet California's energy standards (Title 24, Part 6).
• Fire separation. In Los Angeles, exterior walls less than 5 feet from the property line must be 1-hour fire-resistance rated, or less than 3 feet if the unit has sprinklers. If the garage is attached to the house, Portland, Oregon, says dwellings must be separated by walls and floors "having not less than a one-hour fire-resistance rating."
• Furnaces and water heaters. Federal Way says fuel-burning appliances left in the converted space still need combustion air. Areas containing them "shall not open into a bedroom," and bedrooms may not have windows or doors that open into a garage.
• Separate systems. Los Angeles requires a separate electrical panel and a separate water shutoff for an ADU. Portland requires an ADU's electrical circuits to be completely independent of the main home's.

In California, fire sprinklers are required in an ADU only if the main home must have them. [1][2][3][10]

Fees and utility connections in California

California limits fees on conversions:

• Utility connections. An ADU or junior ADU made from existing space can't be treated as a new residential use for utility connection fees or capacity charges, unless it is built along with a new single-family home. It can't be required to have a new or separate utility connection either.
• Impact fees. None on an ADU of 750 square feet of interior livable space or less, or a junior ADU of 500 square feet or less. A larger ADU can be charged a share of the fee based on its square footage compared with the main home's.
• School fees. School districts may charge fees only on ADUs over 500 square feet.

Other states have their own fee limits. See your state page and our ADU cost guide. [3]

What a garage conversion costs

UC Berkeley's 2021 statewide survey of California ADU owners reported costs for all ADU types together. It found that the median cost to build an ADU was $150,000, or $250 per square foot, and that 37 percent of new ADUs cost less than $100,000.

See our ADU cost guide and ADU financing guide for more on costs and ways to pay. [11]

If your garage was already converted without a permit

In California, a city may not deny a permit for an unpermitted ADU built before January 1, 2020, just because it breaks building standards or ADU rules. It may still deny the permit if fixing a violation is needed to protect health and safety, or if the building is "substandard" under state law. Before applying, you may get a confidential inspection from a licensed contractor to see what work is needed.

Los Angeles has a separate path for these units under the state law known as AB 2533. Its bulletin lists the kinds of proof it accepts that a unit was built before 2020, such as rent registration records, contractor bills, utility bills or a dated lease. [2][3]

Questions people ask