A garage conversion sounds straightforward: the walls and roof are already there, so how hard can it be? Cyrus Poudat has seen California homeowners spend $40K thinking they were almost done, only to discover the slab cannot pass code, the electrical panel cannot carry the load, and the city wants the sewer lateral scoped. Done well, garage conversions are still the best ADU value in California — but only when the scope is honest from day one.
No replacement parking required
California state law forbids cities from requiring replacement parking when a garage is converted to an ADU. Cyrus Poudat regularly cites this on California projects when planners try to impose tandem driveways or carports as a condition.
Slab and foundation
Most California garage slabs were poured without a vapor barrier or proper footings for habitable space. Cyrus Poudat opens at least one inspection cut early to confirm thickness and reinforcement before committing to a finish floor.
Insulation and ceiling height
Garages typically have low or sloped ceilings designed for cars. Cyrus Poudat checks the 7'6" minimum ceiling height for California habitable rooms before assuming the existing roof can stay. Adding insulation often shaves 4–6 inches off finished height.
Egress and natural light
A bedroom needs an egress window. Garage walls usually do not have one. Cyrus Poudat budgets $3K–$6K per California project for cutting new openings in a structural wall, including header and shear adjustments.
Utilities
Even small ADUs need a kitchen, bathroom, water heater and HVAC. Cyrus Poudat plans for an electrical subpanel, a new sewer tie-in, and almost always a tankless water heater to fit California garage footprints.
Detached garages: easier permit
Detached garage conversions in California qualify for the ministerial 60-day approval and have looser fire-separation rules than attached. Cyrus Poudat usually recommends starting with the detached structure if a property has both.
Realistic budget
Cyrus Poudat's California garage-conversion projects land between $90K and $160K all-in for a 350–500 sq ft unit. Anything quoted below $80K is missing line items that will surface during construction.