How much does it cost to build an ADU in Los Angeles? (2026)
In 2026, a permitted, move-in-ready ADU in Los Angeles typically costs $150,000 to $400,000 or more — roughly $300 to $550 per square foot for a new detached unit, including design, permits, construction, and finishes. A garage conversion is the cheapest path at $80,000 to $150,000. The biggest cost swing usually isn't square footage; it's whether your parcel sits under a hazard overlay that adds review and expense.
Cost at a glance (2026, Los Angeles)
| ADU type | Typical all-in | Per square foot | Notes |
|---|---|---|---|
| Garage conversion | $80,000–$150,000 | ~$150–$300/sq ft | Cheapest; reuses an existing structure |
| Attached new build | $150,000–$300,000 | $250–$400/sq ft | Shares a wall with the main house |
| Detached new build | $200,000–$400,000+ | $300–$550/sq ft | Most common; standalone backyard unit |
| Hillside / custom / high-end | $400,000+ | $650+/sq ft | Site access, grading, custom design |
Ranges reflect 2026 market reporting from Los Angeles ADU builders and vary by parcel. Sources: GreatBuildz, CALI ADU, LADU.
For context, the median ADU permit valuation in LA climbed from about $74,000 in 2018 to roughly $200,000 in 2026 as ADUs shifted from cheap garage conversions to full new-construction homes. And ADUs are no longer niche: the City of LA permitted 6,626 ADUs in 2024 — about 43% of all newly permitted housing units that year (Crosstown LA).
What drives the cost
- Type of build
- Converting an existing garage is far cheaper than pouring a new foundation for a detached unit.
- Size
- Under California state law a city must ministerially approve a detached ADU up to 800 sq ft even where local rules would say no (Cal. Gov. Code §66323), and can't cap your max size below 850 sq ft — 1,000 for two or more bedrooms (§66321).
- Site conditions
- Hillside lots, poor soil, long utility runs, and difficult access push per-foot costs up fast.
- Overlays
- Fire (VHFHSZ), flood, hillside, coastal, and historic overlays can add engineering, review time, and cost — the factor most homeowners don't price in until a builder flags it.
- Soft costs
- Design, plans, permits, and utility hookups commonly add $15,000–$50,000+ on top of construction.
Before you pay for a build estimate
Builders quote off feasibility — is the parcel eligible, what's the max footprint, is it in an overlay that adds cost. Knowing that first turns a sales call into a real number. You can confirm eligibility yourself through LADBS and the LA County planning ADU page, hire an ADU consultant, or run your address through BackyardCheck for an instant verdict — by-right size, height, and setbacks with a code citation for each, and a $99 report that adds detailed cost and rent ROI. It's the cheap first step before you pay anyone for plans, not a substitute for a designer or a contractor's bid.
ADU cost in Los Angeles: common questions
A permitted, move-in-ready ADU typically costs $150,000 to $400,000 or more — about $300 to $550 per square foot for a new detached unit. Garage conversions start around $80,000 to $150,000.
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