Garage Conversion ADUs

A garage conversion turns a structure you already own into a dwelling without a new footprint, new foundations or a new roof. State law treats it as the easiest ADU to approve. Government Code section 66323(a)(1) requires a city to approve one ADU within the existing space of a single-family home or an existing accessory structure, with up to 150 square feet of expansion to accommodate entry and exit, side and rear setbacks only as needed for fire and safety, and no replacement of the parking spaces the garage held.

We have designed ADUs since 2017, across more than 1,500 projects in Los Angeles County and Orange County since 2015, and garage conversions are the largest share of them.

The structure keeps its footprint. The dwelling inside it has to meet the Building Code as a dwelling: ceiling height, egress, light and ventilation, insulation and energy, fire separation from the main house where the garage is attached, plumbing and electrical sized for a kitchen and a bath, and a foundation that carries the new loads. Most garage slabs and framing need work, and the plan set has to show it. The zoning side is short: no setbacks beyond fire and safety, no replacement parking, and no new area beyond the 150 square feet.

Some cities add a condition the statute does not contain. In Gardena in 2026, planning staff required an existing garage and rumpus room to meet four-foot setbacks and building-separation standards before they could be converted, because a 1963 permit for the room had expired without completion. We separated the two questions the city had combined, whether the building exists and whether its permit history is complete, and requested technical assistance from HCD. HCD responded that requiring an existing structure to be permitted in order to qualify for conversion was incorrect, citing section 66322(b) and its health and safety conditions. The planner withdrew the comment, and the building permit has issued.

• Lot and structure read: zone, overlays, the garage’s permit record, slab and framing condition, utility routes, and the distance to the main house.
• A layout that works in the width a garage gives, usually a studio or one bedroom with a full kitchen, sized to the existing walls plus the 150 square feet where it buys a proper entry.
• Structural coordination with a licensed engineer for the slab, the new openings and any roof work.
• Permit management through plan check to issuance, with any correction the code does not support answered in writing.

Do I have to replace the parking?

No. State law does not allow a city to require replacement parking when a garage is converted to an ADU.

Can I enlarge the garage?

By up to 150 square feet beyond its existing dimensions, and only to accommodate entry and exit. Beyond that it is a new-construction ADU with its own rules, including four-foot side and rear setbacks under section 66314(d)(7).

What if the garage was never permitted?

That is a separate question from whether it can be converted. HCD has said a city cannot require the structure to have been permitted to qualify; the converted unit must meet health and safety standards. Unpermitted structures often need legalization work alongside the conversion, which we handle.

How long does approval take?

A city must act on a complete ADU application within 60 days. The time before that, getting the set complete, is where most of the schedule goes.