How Much Does an ADU Cost in Los Angeles? (2026 Guide)

Ask three contractors what an ADU costs and you'll get a shrug, a lowball, and a number with nothing behind it. Here's the honest version — the same ranges we quote clients across the San Fernando Valley and greater LA in 2026.

The short answer

Project type	Typical turnkey cost	Typical timeline
Garage conversion (≈400 sq ft)	$100,000 – $180,000	3–5 months total
Attached ADU / addition-style	$180,000 – $300,000	6–10 months total
Detached new-build ADU (600–1,200 sq ft)	$250,000 – $400,000+	8–12 months total

"Turnkey" means livable and rentable: construction, fixtures, flooring, kitchen, mini-splits — not a shell. If a bid is dramatically below these ranges, find what isn't in it. Usually it's the site work, the utilities, or the finish level.

What actually drives the price

New foundation vs. existing slab. Garage conversions win on cost because the roof, slab, and walls exist. A detached unit buys all three new.
Utilities. Sewer connection distance, trenching, and whether your electrical panel needs a 200-amp upgrade can swing the budget $10k–$40k. We price this at the first site visit, not as a surprise later.
Size — but less than you'd think. Kitchens and bathrooms are the expensive rooms, and every ADU has them. A 1,000 sq ft unit does not cost double a 500 sq ft unit.
Finish level. Rental-grade durable finishes vs. match-the-main-house custom: same walls, very different checkout total.
Access. Tight side yards and hillside lots slow concrete and framing. Flat lot with driveway access to the backyard is the best case.

Soft costs nobody mentions

Plans, structural engineering, Title 24 energy calcs, city plan check, permit fees, and utility fees typically run $15,000–$35,000 depending on the city and design. Pre-approved standard plans (City of LA has a program) can trim design costs and speed approval. Any quote that ignores soft costs is a quote for part of your project.

The rent math

Valley and LA ADUs are renting around $1,800–$2,800/month in 2026 depending on size and neighborhood. Against a $150k garage conversion, that's gross payback in roughly 5–8 years; a $300k detached unit pencils out around 9–12. After payback it's income — and the county reassesses property tax only on the value the ADU adds, not your whole house.

How to start without wasting money

Before you pay anyone for plans, get the two answers that decide everything: what your lot allows, and what utilities will really cost. We check both in a free site visit — then you can decide with real numbers on the table.

Thinking about it? See our ADU construction page or get a free ADU site check — we'll tell you what your property can actually do.