ADU vs. Garage Conversion: The 2026 Comparison

Same square footage. Half the parking. Very different permits.

Detached ADU or converted garage — the choice comes down to whether you want to keep the garage. Both add legal second dwellings. The garage conversion is typically cheaper and faster; the detached ADU adds more real property value.

Why this makes sense right now

California SB 9 and similar state laws have made garage conversions substantially easier since 2020. Los Angeles Department of Building & Safety permitted 5,400 garage conversions in 2024 alone. Statewide, garage conversions represent 22% of all ADU permits.

The math: garage conversion saves ~$120K vs. detached ADU. Loses parking. Fewer options for future expansion or replacement.

The layout — head-to-head

Existing structure

• Detached ADU: none (new build)
• Garage conversion: existing garage frame

Cost turnkey

• Detached ADU: $180K-$450K
• Garage conversion: $80K-$180K

Timeline

• Detached ADU: 6-12 months
• Garage conversion: 3-6 months

Parking impact

• Detached ADU: preserves garage
• Garage conversion: eliminates 1-2 spaces

Permit path

• Both: standard ADU permit (state-dependent)
• Garage conversion: also requires change-of-use permit

Resale value added

• Detached ADU: 60-80% of build cost
• Garage conversion: 40-60% of build cost

Rental income (2026 typical, LA metro)

• Detached ADU: $1,800-$2,600/month
• Garage conversion: $1,400-$2,000/month

Future flexibility

• Detached ADU: separable, can sell as condo in some jurisdictions
• Garage conversion: attached to primary, less flexible

Financing math

$250K detached ADU HELOC at 8.75% = $1,830/month interest. $130K garage conversion HELOC = $950/month interest. Detached ADU generates ~$400/month more rental. Ten-year total cost vs. income favors detached ADU by ~$25K.

Choose the detached ADU if...

• Parking preservation matters (city with strict street parking)
• Maximum resale value matters
• Long-term rental income optimization
• Have budget + HELOC/HomeStyle access

Choose the garage conversion if...

• Budget under $180K
• 3-6 month timeline
• Existing garage in good structural condition
• Parking loss is acceptable
• Fastest path to rental income

The quiet part.

Garage conversions are the "quick and cheap" ADU. Detached ADUs are the "right and expensive." Both work. Both add legal dwelling units. Both generate rental income.

The mistake most families make: converting a garage they later realize they needed. Parking, workshop, storage — the garage's original function doesn't come back once it's a bedroom. If you use the garage even monthly for its original purpose, the detached ADU is worth the extra $120K.

Related guides

• Multi-Generational Living: ADU Design Guide — the compound approach
• Backyard Cottage vs. Home Addition — the addition alternative
• ADU for Adult Children Independent Living — the family use case

The waitlist is open

The PERCH marketplace opens with ADU builders across detached and conversion categories. The Financing Finder sorts loan structures. Eight questions.

Same lot. Different structure. Different loss (money vs. parking). Pick the one you'll regret less in ten years.