California’s ADU laws, expanded several times since 2017, have made backyard cottages, garage conversions and junior ADUs a regular part of the market. A permitted ADU can add rental income and flexibility. An unpermitted one can add risk.
Confirm the permit
Ask for the building permit and final inspection sign-off. Compare the permit description with what is actually there: square footage, kitchen, bathroom, and whether it was approved as an ADU or as something else, such as a home office or a garage.
Tell your inspector
Many inspectors charge an additional fee for an ADU and treat it almost like a second house. Make sure it’s included in the scope.
What to inspect
- Electrical: is there a separate subpanel or meter? Is the feeder sized correctly?
- Plumbing: does the ADU have its own water heater? How does the sewer line connect?
- Heating and cooling: mini-splits are common; check condensate drainage.
- Fire separation: for attached units and conversions.
- Egress: windows and doors large enough in sleeping areas.
- Smoke and CO alarms: required in the ADU too.
- Drainage: new structures often change how water moves across a lot.
Garage conversions
Converted garages often have slab-on-grade floors that were never insulated or vapor-protected, low ceilings, and electrical circuits added later. Look for moisture at the base of walls and confirm the permit.
Renting it out
If you plan to rent the ADU, check local rules on short-term rentals and the rent rules that may apply.