What is an Accessory Dwelling Unit (ADU)?
An Accessory Dwelling Unit (ADU) is a secondary housing unit built on the same lot as a single-family or multi-family residence. In the case of a garage conversion, the existing structure is remodeled into a living space complete with:
A kitchen
A full bathroom
A sleeping area
Separate entrances
Garage conversion ADUs are legal in California—but you must secure the proper permits before starting any construction.
Why Garage Conversions Are Popular in California
Due to California’s updated housing laws, garage conversions are now more accessible than ever. Here's why homeowners are choosing this route:
Cost-effective: Utilizes an existing structure
Bypasses new construction limitations: Avoids new foundation and framing
Quicker project timeline
Exempt from impact fees (if under 750 sq. ft.)
Great ROI in high-rent markets
Step-by-Step Guide to Getting a Garage Conversion ADU Permit in California
1. Understand State and Local ADU Laws
While California has passed statewide legislation allowing ADUs on most residential lots, your local city or county may have additional requirements. You’ll need to check with:
Your local planning department
The California Department of Housing and Community Development (HCD)
Key laws include:
SB 13, AB 68, AB 881 (2020): Streamline ADU approval
AB 670: Allows ADUs in HOA-regulated areas
AB 3182: Prohibits restrictions on ADU rentals
2. Check Zoning and Lot Eligibility
Verify that your garage is on a residentially zoned lot. Your lot must allow for:
At least one ADU and one Junior ADU
Setback compliance (some areas waive setbacks for existing garages)
Proper utility access
If your property qualifies, you can proceed to the planning phase.
3. Hire a Professional for Design and Planning
It’s best to work with:
An architect or residential designer familiar with ADUs
A structural engineer (if modifying the foundation or adding stories)
A contractor licensed in California (B license)
Plans must comply with:
California Building Code (CBC)
Title 24 energy compliance (thermal insulation, ventilation, windows)
Local municipal codes
Your plan should include:
Floor plans
Site plans
Elevations
Structural details
Fire safety measures
4. Submit Your Permit Application
Once your architectural plans are ready, submit them to your local building department. Required documents may include:
Completed ADU permit application
Site plan and construction drawings
Title 24 Energy Report
Historic review documents (if applicable)
Permit fees
In California, local agencies must approve ADU applications within 60 days of a complete submission.
5. Get Utility Approvals (if needed)
Garage conversions typically connect to existing systems, but you may need:
New plumbing or electrical meters
Backflow prevention
Sewer capacity confirmation
Many cities waive connection fees for garage ADUs under 750 sq. ft.
6. Schedule a Pre-Construction Inspection
Before breaking ground, your local department may require a pre-construction meeting with a building inspector. This ensures:
Your project matches approved plans
Your site is ready for construction
7. Begin Construction
Once your permit is issued, you can begin remodeling your garage. Ensure your contractor:
Follows the approved architectural and engineering plans
Complies with fire safety, egress, and ADA requirements
Manages waste and noise during construction hours
8. Schedule Inspections During Construction
At various stages—foundation, framing, electrical, insulation, plumbing—you’ll need to call for inspections.
Pass each stage before proceeding to the next to avoid delays.
9. Final Inspection and Certificate of Occupancy
When construction is complete:
Call for a final inspection
Resolve any correction notices
Once passed, you’ll receive your Certificate of Occupancy
You can now legally rent out or inhabit the new ADU!
Common Pitfalls to Avoid
Not checking local rules: Cities like San Francisco and Los Angeles have nuanced regulations.
Skipping energy compliance: Title 24 forms are required for all conversions.
Assuming it's “just a remodel”: ADUs must be permitted—even if the garage already has electricity or plumbing.
Choosing an unlicensed contractor: Always verify credentials with the Contractors State License Board (CSLB).
