LA Cost Guide
How Much Does an ADU Cost in Los Angeles? (2026)
Real per-square-foot pricing by ADU type, permit costs and timeline under SB 543, and where the money actually goes.
Updated July 2026 · Sourced & cited below
Quick answer: a garage conversion ADU in LA runs $100,000–$150,000, a mid-size 600–800 sq ft ADU $200,000–$250,000, and a larger 800–1,200+ sq ft detached ADU $250,000–$350,000+.
| ADU type / size |
Typical total cost |
Cost / sq ft |
| Garage conversion (~400–500 sq ft) |
$100,000 – $150,000 |
$300 – $450 |
| Attached or new 600–800 sq ft ADU |
$200,000 – $250,000 |
$300 – $400 |
| Detached 800–1,200+ sq ft ADU |
$250,000 – $350,000+ |
$250 – $400 |
Ranges are estimates from LA-based ADU builder cost guides (sources below), not quotes. Premium finishes, difficult site access, or long utility runs can push any of these ranges to $500–$700+ per square foot.
What drives the cost
ADUs have more soft costs (design, permits, utilities) than any other home project — and a 2026 state law just changed the timeline.
- Design & plans: $8,000–$20,000 for a full plan set (architectural, structural engineering, Title 24 energy compliance). Garage conversion plans run slightly less, about $8,000–$10,000, since less of the structure is new.
- Permits & city fees (LA/DBS): plan check plus permit issuance plus impact fees typically total $5,000–$15,000. One major money-saver: California state law exempts any ADU under 750 sq ft of interior living space from local impact fees — staying under that line is the single easiest way to cut permit costs.
- Timeline law (SB 543, 2026): LADBS must now determine your application "complete" within 15 business days, then has 60 calendar days to approve or deny. Projects using one of LA's 20+ pre-approved ADU plans can be approved in as little as 21–30 days; custom designs typically take 2–4 months through plan check.
- Utilities: sewer, water, and electrical panel upgrades or new trenching vary hugely by lot — a unit far from existing hookups costs meaningfully more than one built right next to them.
- Type of ADU: garage conversions reuse an existing slab and walls, which is why they're consistently the cheapest path; ground-up detached units cost the most in total dollars.
Cost breakdown by component
| Design & plans (full ADU) | $8,000 – $20,000 |
| Design & plans (garage conversion) | $8,000 – $10,000 |
| Permits, plan check & impact fees | $5,000 – $15,000 |
| Construction (garage conversion) | $300 – $450 / sq ft |
| Construction (new build, ground-up) | $250 – $400 / sq ft (up to $650+ premium) |
| Utilities / site work | Varies — biggest wildcard in the budget |
Money-saving tips
- Stay under 750 sq ft of interior living space to skip local impact fees entirely — a real, state-mandated savings, not a workaround.
- Use one of LADBS's pre-approved ADU plans if your lot allows it — you skip months of custom plan check and get approval in as little as 21–30 days.
- Convert the garage instead of building new if you have one to spare — you keep the slab and walls, the largest cost driver in any ADU.
- Build close to existing utility hookups. A unit that needs 100 feet of new sewer trenching costs meaningfully more than one built next to the main line.
- Get bids from at least 3 licensed ADU-specific contractors — general remodelers and ADU specialists often price the same plan set very differently.
Red flags when hiring
- No CSLB license, or a license that shows expired, suspended, or revoked on the free Instant License Check at cslb.ca.gov.
- Anyone offering to build an ADU without pulling permits to save money. An unpermitted ADU can't legally be rented, won't pass a future home-sale inspection, and voids your insurance if something goes wrong.
- A bid far below 3–4 comparable quotes with no explanation for the gap — usually unlicensed subs or a plan to under-bid then charge change orders.
- Asking for more than the legal deposit cap — 10% of contract price or $1,000, whichever is less.
- No written contract, or a contract that doesn't list the specific plan set, materials, and payment schedule.
FAQ
How much does it cost to build an ADU in Los Angeles in 2026?
A garage conversion runs $100,000–$150,000, an attached or new 600–800 sq ft ADU runs $200,000–$250,000, and a detached 800–1,200+ sq ft ADU runs $250,000–$350,000 or more, before premium finishes or difficult site work.
Is a garage conversion cheaper than building a new ADU?
Yes — garage conversions typically run $100,000–$150,000 because they reuse the existing slab and walls, versus $200,000–$350,000+ for an attached or ground-up detached unit of similar size.
How long does ADU permitting take in LA in 2026?
Under SB 543, LADBS must confirm your application is complete within 15 business days and then has 60 calendar days to approve or deny it. Projects using a pre-approved plan can be approved in as little as 21–30 days; custom designs typically take 2–4 months through plan check.
Do I need a permit to build an ADU in Los Angeles?
Yes — every ADU in Los Angeles requires an LADBS permit. Permit, plan check, and impact fees typically total $5,000–$15,000, though ADUs under 750 sq ft of interior living space are exempt from local impact fees by state law.
How can I lower the cost of building an ADU?
Stay under 750 sq ft to skip impact fees, use a pre-approved plan design to skip months of custom plan check, and convert an existing garage instead of building ground-up if you have one available.
Sources:
GreatBuildz — cost to build an ADU in LA ·
CALI ADU — ADU cost LA 2026 ·
Andalusia Drafting — LA ADU guide 2026 (SB 543, LADBS rules) ·
My Cali Builders — ADU permit cost & timeline ·
CSLB — verify a contractor's license