The structural choice that drives everything
The first design decision for any ADU is: do you build it standalone (detached) or attached to your main house? It affects cost, timeline, privacy, and ultimately rental income.
Detached ADU — pros and cons
Pros: Maximum privacy, highest resale value, qualifies for AB 1033 condo conversion, easiest to rent.
Cons: Higher cost (a property-specific written estimate), needs more lot space, full new foundation.
Attached ADU — pros and cons
Pros: Can share a wall and some utility paths, uses less yard space, and may simplify portions of the scope. Final pricing requires a property-specific written estimate.
Cons: Less privacy for tenants, often lower rental rate, shared wall creates noise considerations.
How to decide
| Priority | Best Choice |
|---|---|
| Maximum rental income | Detached |
| Lowest cost | Attached (or garage conversion) |
| Resale flexibility (AB 1033) | Detached |
| Multigenerational family | Either; attached preferred for caregivers |
| Small lot | Attached |
Hybrid options
- Garage conversion + addition: Convert garage and add 200–400 sf
- Above-garage ADU: Two-story unit on existing garage footprint
Both blend attached and detached economics.
See examples in your city
Browse our portfolio across LA, OC, and the Inland Empire or book a free site evaluation.
Frequently Asked Questions
Is a detached ADU more expensive than attached?
Typically yes — 10–25% more because of new foundation, exterior walls, and roof.
Do attached ADUs need separate entrances?
Yes, state law requires an exterior door that does not enter through the main house.
Can I convert an attached ADU to detached later?
Not practically — it would require demolishing and rebuilding.
Do appraisers value detached higher than attached?
Per square foot, often yes — detached typically appraises 5–12% higher than equivalent attached.
Which is easier to permit?
Both are equally permissible under state law; some cities slightly favor attached due to setback flexibility.
Related Vision ADU Resources
- Garage Conversion ADU Permits in California (2026 Step-by-Step)
- ADU Setback Requirements in California (2026 State Minimums + City Rules)
- ADU Height Limits in California (2026 State Rules + City Variations)
- ADU Parking Rules in California (2026)
- ADU Contractor in Long Beach
- ADU Contractor in Burbank
- Los Angeles County ADU Builder
- Orange County ADU Builder
- Inland Empire ADU Builder
- 2026 ADU Cost Calculator
- All Vision ADU Service Areas