Garage Conversion vs. New Construction ADU: Which Is Right for You?
Barak Golan ·
The Great ADU Debate: Convert or Build New?
This is the #1 question we get from homeowners considering an ADU. Both options have distinct advantages, and the right choice depends on your property, budget, goals, and timeline.
Garage Conversion
Pros:
- Lower cost: $80k–$150k vs. $150k–$250k for new construction
- Faster timeline: 4-6 months vs. 8-14 months
- Simpler permitting: Existing structure means less plan check scrutiny
- No parking replacement required under California law (SB 13)
- Smaller carbon footprint: Reusing an existing structure
Cons:
- Size limitations: Limited to your garage's footprint (typically 400-600 sq ft)
- Ceiling height constraints: Standard garages have 8-foot ceilings
- Foundation concerns: Existing slab may need reinforcement
- Layout constraints: Working within existing walls limits design options
- Loss of garage storage: You'll need alternative storage solutions
Best For:
- Budget-conscious homeowners
- Properties with two-car garages not being fully used
- Those who want rental income quickly
- First-time ADU builders
New Construction ADU
Pros:
- Maximum size: Up to 1,200 sq ft — room for 2 bedrooms and 2 baths
- Complete customization: Design exactly what you want from scratch
- Higher rental income: Larger, newer units command premium rents
- Greater property value increase: $80k–$150k vs. $150k–$250k
- Modern building standards: Built to latest codes and energy requirements
- Keep your garage: Don't sacrifice your parking or storage
Cons:
- Higher cost: $150k–$250k is a significant investment
- Longer timeline: 8-14 months from design to move-in
- More complex permitting: New construction requires more extensive plan review
- More disruption: Foundation excavation, concrete trucks, crane lifts for trusses
- Yard space: You'll lose some backyard area
Best For:
- Homeowners who want maximum rental income
- Those planning to house family members long-term
- Properties with large backyards
- Homeowners who need their garage
- Those planning to sell the ADU separately (under AB 1033)
The Numbers Comparison
| Factor | Garage Conversion | New Construction |
|---|---|---|
| Average Cost | $80k–$150k | $150k–$250k |
| Timeline | 5 months | 11 months |
| Size | 450 sq ft | 900 sq ft |
| Monthly Rent | $2,000–$2,800 | $2,400–$3,500 |
| Annual Income | $24,000–$33,600 | $28,800–$42,000 |
| Property Value Add | $100k–$175k | $175k–$280k |
| ROI Timeline | 6 years | 7 years |
Our Recommendation
If you're on a budget or want to dip your toes into ADU ownership, start with a garage conversion. If you're making a long-term investment and have the budget, new construction offers superior returns.
Not sure which is right for you? Get a free consultation and we'll assess your property for both options.