When Los Angeles homeowners decide to build an ADU, one of the first decisions is attached versus detached. Both types qualify under California’s ADU laws, but they differ significantly in cost, privacy, rental appeal, and construction complexity. This guide breaks down the key differences to help you choose the right ADU type for your Los Angeles property.
An attached ADU shares at least one wall with the primary dwelling. This includes: converting an attached garage to an ADU, adding a new unit onto the side or rear of the main house, or converting interior space (basement, bonus room) into a separate dwelling unit. Attached ADUs share the primary structure but have a separate entrance and are legally self-contained.
A detached ADU is a fully separate structure on the same lot as the primary dwelling. This includes: converting a detached garage, building a new freestanding unit in the rear yard, or converting an existing outbuilding. Detached ADUs are entirely separate structures from the main house.
| ADU Type | Typical Cost Range |
|---|---|
| Attached garage conversion | $75,000–$130,000 |
| Interior conversion (JADU) | $40,000–$75,000 |
| New attached addition ADU | $145,000–$245,000 |
| Detached garage conversion | $85,000–$145,000 |
| Detached new construction ADU | $145,000–$225,000 |
For rental purposes, detached ADUs command higher rents and attract more qualified tenants in the Los Angeles market. A detached unit provides complete acoustic and visual separation from the primary dwelling — no shared walls, no shared building footprint. LA renters paying $2,500–$4,500/month are sensitive to privacy and prefer a free-standing structure. In practice, detached ADUs in Los Angeles rent for 8–15% more than attached units of equivalent size.
Attached conversions (converting an attached garage) are often the simplest attached ADU path — the slab is already there, the framing is already there. But new attached additions share the structural loads of the main house, requiring more careful engineering review. Detached conversions (detached garage) are clean and self-contained. New detached construction is the most design-flexible but also the most expensive.
APLA’s recommendation based on experience with hundreds of LA ADU projects:
Yes, typically. Detached ADUs add approximately 10–15% more to resale value than attached ADUs of equivalent size, primarily because they deliver higher rental income and are more attractive to tenants. The resale value premium typically justifies the 10–20% higher construction cost of a detached new build vs. an attached conversion.
California ADU law (AB 2221, SB 897) significantly streamlines permitting for both attached and detached ADUs. The same setback requirements (4 ft rear and side for detached ADUs up to 16 ft tall) apply to most Los Angeles properties. APLA evaluates both options for every Los Angeles ADU project.
Yes. APLA (CA Lic #1136359) builds all ADU types throughout Los Angeles. Call (818) 818-4419 for a free ADU feasibility analysis — we evaluate both attached and detached options for your specific property and recommend the best path.
Call: (818) 818-4419
Email: info@aplaconstruction.com
CA General Contractor License #1136359
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