Got an underutilized garage collecting dust and old holiday decorations? Converting it into a legal Accessory Dwelling Unit (ADU) could be your smartest move yet. Whether you’re eyeing rental income, need space for aging parents, or want a home office that actually feels separate from home, a garage conversion offers maximum return with minimal site disruption.

New to ADUs? Our comprehensive guide covers everything you need to know: What Is an ADU (and Why You Might Want One).

Step 1: Master Your Local Regulations

Skip the Pinterest boards for now—your first stop is the city planning department website. Garage conversions must comply with local ADU ordinances that typically address:

• Setback requirements from property boundaries
• Size limitations (both minimum and maximum square footage)
• Parking mandates (some cities waive these for garage conversions)
• Height restrictions and design standards
• Owner-occupancy rules (varies by location)

California cities have dramatically relaxed ADU restrictions in recent years, but regulations still differ significantly between neighboring municipalities. A few hours of research upfront can save months of headaches later.

Step 2: Assess Your Garage’s Readiness

Not every garage is conversion-ready. Before investing in plans, evaluate whether your structure can support habitable space. Key factors include:

• Foundation stability (no major settling or cracking)
• Structural framing adequate for living loads
• Ceiling height meeting code minimums (typically 7-8 feet)
• Utility access for water, sewer, electrical, and gas connections
• Drainage and moisture control

Consider hiring a structural engineer for older garages or those showing signs of wear. Better to identify issues early than discover them mid-construction.

Step 3: Design for Function and Compliance

Smart design makes the difference between a cramped converted garage and a desirable living space. Your ADU must include all elements for independent living:

Kitchen Requirements:

• Sink, refrigerator, and cooking appliance
• Adequate counter space and storage
• Proper ventilation and electrical capacity

Bathroom Essentials:

• Full bathroom with shower/tub
• Mechanical ventilation
• Proper waste line connections

Living Space Considerations:

• Natural light from multiple sources
• Proper insulation and climate control
• Energy code compliance (California’s Title 24, for example)
• Emergency egress requirements

Many successful conversions replace the garage door with large windows or French doors, dramatically improving natural light while maintaining street appeal.

Step 4: Navigate the Permit Process

Plan review is where many DIY dreams meet reality. You’ll typically need:

• Building permit for the overall conversion
• Trade permits for electrical, plumbing, and HVAC work
• Structural documentation if modifying framing or foundation
• Energy compliance reports as required by local code

Submit complete, professional drawings to minimize review cycles. Plan review timelines vary wildly—from weeks in ADU-friendly cities to months in locations with permitting backlogs. Some jurisdictions offer expedited review for ADU projects.

Step 5: Execute the Construction

With permits in hand, construction typically follows this sequence:

Phase 1: Demolition and Site Prep

• Remove garage doors, outdated electrical, and non-compliant framing
• Address any foundation or structural issues

Phase 2: Rough Construction

• Frame interior walls and ceiling modifications
• Install insulation and vapor barriers
• Run electrical, plumbing, and HVAC rough-in

Phase 3: Finish Work

• Drywall installation and finishing
• Flooring, cabinetry, and trim work
• Appliance and fixture installation

Each phase requires inspection approval before proceeding. Build relationships with your local inspectors—they’re your partners in creating a safe, legal ADU.

Step 6: Cross the Finish Line

Final inspection and Certificate of Occupancy (CO) issuance mark the official completion of your legal ADU. This document allows you to rent the space, claim it as a separate unit for tax purposes, and ensure future buyers understand its legal status.

The Professional Advantage

ADU projects differ significantly from typical home renovations. The regulatory complexity, inspection requirements, and specialized knowledge needed often justify working with experienced professionals:

Design Professionals: Architects or designers with ADU portfolios understand space optimization and code compliance nuances.

Specialized Contractors: General contractors experienced in ADU work navigate permit processes efficiently and avoid common pitfalls.

Permit Consultants: In slower jurisdictions, permit expediters can significantly reduce timeline uncertainty.

Bottom Line

A well-executed garage conversion can add substantial value to your property while creating much-needed housing. The key lies in understanding your local requirements, honestly assessing your garage’s condition, and assembling the right team for execution. With proper planning and professional guidance, you can transform that underused space into a beautiful, code-compliant ADU that serves your family’s needs for years to come.

Ready to get started? Begin with a visit to your local planning department or ADU resource center to understand the specific requirements in your area.