An ADU in Los Angeles typically costs $130,000 to $450,000 total, depending on the type of unit. Garage conversions run cheapest at roughly $130,000–$220,000, attached ADUs land around $150,000–$300,000, and detached, ground-up ADUs run the highest at $220,000–$450,000 — driven mainly by square footage, site conditions, and finish level.
ADU Cost by Type in Los Angeles (2026)
| ADU Type | Typical Total Cost | Cost Per Square Foot |
|---|---|---|
| Garage conversion | $130,000 – $220,000 | $150 – $300/sq ft |
| Attached ADU | $150,000 – $300,000 | $250 – $450/sq ft |
| Detached ADU (new build) | $220,000 – $450,000 | $300 – $450/sq ft |
| Junior ADU (within existing space) | $60,000 – $150,000 | varies — minimal new structure |
Ranges reflect fully built and permitted projects across multiple current LA-area cost-guide sources. Individual lots, permit paths, and finish levels will move these numbers.
What Drives the Cost
The same square footage can price out very differently depending on a handful of factors that show up on almost every ADU bid in Los Angeles.
Foundation and site conditions
A sloped lot, poor soil, or the need to relocate utilities before a detached ADU can be built adds cost before framing even starts. Garage conversions skip most of this since the foundation already exists.
Square footage and layout complexity
Cost per square foot tends to drop slightly as unit size increases, but a more complex layout (multiple rooms, a full second bathroom) raises labor cost regardless of total size.
Utility connections
New electrical panels, sewer lateral work, and separate gas/water connections can add tens of thousands of dollars, especially on older lots where the existing utility infrastructure needs upgrading to support a second unit.
Permit path and plan complexity
A standard-plan or pre-approved ADU design (offered by LA County and several cities) is faster and cheaper to permit than a fully custom design — see the ADU permit process guide below for how that path works.
Finish level
Builder-grade finishes sit at the low end of every range above; higher-end cabinetry, flooring, and fixtures can push a project toward the top of its range or beyond it.
A Note on These Numbers
These ranges are drawn from current, publicly published 2026 ADU cost guides covering the Los Angeles and Southern California market — not a single contractor's marketing estimate. Actual bids vary by lot, scope, and contractor, so treat this as a planning range, not a quote.
The most reliable way to get an accurate number for your specific property is a bid from a licensed, CSLB-verified contractor who can walk your lot and see the actual site conditions, existing utility connections, and structure (if converting a garage).
Verify Before You Sign
Confirm any contractor is actually licensed before you commit to a bid.
Frequently Asked Questions
What is the cheapest way to build an ADU in Los Angeles?
A garage conversion is typically the least expensive path, usually $130,000–$220,000, since the existing foundation, walls, and roof are reused rather than built from scratch. A junior ADU — carved from existing living space inside the main house — can run even lower.
Does the cost of an ADU include permits?
Not usually — the ranges above are for construction. Permit, design, and utility-connection fees are typically an additional $25,000–$60,000 on top of construction cost, though this varies by jurisdiction and project size.
Is a detached ADU always more expensive than an attached one?
In most cases, yes, because a detached unit requires a full new foundation, roof, and standalone utility connections. An attached ADU can share a wall, foundation edge, or utility tie-in with the main house, which usually lowers cost.
Can I get a more accurate ADU cost estimate for my property?
A general price range like this one is a starting point for budgeting. For a number specific to your lot, a licensed contractor needs to see the site — soil conditions, existing utilities, and access all affect the final bid.
Ready to Get a Real Number for Your Lot?
General ranges only go so far. A licensed, CSLB-verified ADU contractor can walk your property and give you an estimate based on your actual lot, not a statewide average.
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Cost data compiled from current published Los Angeles-area ADU cost guides, August 2026. Verify current pricing with a licensed contractor before budgeting a project.