How much does a detached ADU cost in LA in 2026?

$320K–$520K all-in for 600–1,000 sqft. Access, panel, and finish move the number.

Does LA require parking for a new detached ADU?

No within ½ mile of transit — covers most of LA County.

How much does a detached ADU cost in the Bay?

$450K–$720K all-in. SF, Berkeley, and Peninsula coastal cities top the band.

How long does SF DBI take to permit?

8–12 months in SF. Oakland 4–6. San Jose pre-approved 6–8 weeks.

California Detached ADU.

Detached ADUs across Greater LA — own walls, roof, kitchen, bath, address. We handle LADBS submittal slab to certificate of occupancy.

Detached ADUs across the Bay — SF DBI, Oakland, Berkeley, San Jose, with a feasibility note before contract.

Los Angeles

$320K – $520K all-in

Lot access, panel upgrade, and finish drive the band.

Timeline — 3–5 months for design + LADBS permit, then 4–6 months on-site.

Los Angeles Detached ADU →

San Francisco Bay Area

$450K – $720K all-in

Hillside, soft-story foundation, PG&E coordination drive cost.

Timeline — 5–8 months for design + city permit, then 5–7 months on-site.

San Francisco Bay Area Detached ADU →

Scope — what we deliver.

Site walk + zoning check
Full plan set + Title 24
LADBS permit
Foundation to finishes
CofO + warranty

Permits look different in LA vs the Bay.

Los Angeles — permit notes

LADBS pre-approved plans compress permit to 4–6 weeks.
Hillside, HPOZ, Coastal add review.
200A panel upgrade is the #1 cost surprise.
State law allows up to 1,200 sqft as-of-right.

Bay Area — permit notes

SF DBI runs 8–12 months on detached ADUs.
Oakland/Berkeley tighter setback + tree rules.
PG&E adds 8–14 weeks.
WUI fire-zone construction in East Bay hills.

How we think about detached adu.

An ADU is the single highest-ROI piece of construction most California homeowners will ever do — but only when the building separates cleanly from the main house mechanically, acoustically, and legally. We design every unit as if it will be rented to a stranger on day one: independent panel, independent water shutoff, independent address, independent waste line where the lot allows.

The cheap way to build an ADU is to share systems with the primary residence. It works on paper. It fails in year three when the tenant calls the homeowner about a water heater that lives in the main-house garage. Separation costs 6–9% more up front and recovers it within the first turnover.

We refuse to value-engineer the envelope. The walls, roof, and windows are what the building still has in 30 years; the cabinets and fixtures are not. Spend on R-25 walls, R-49 roof, low-e dual-pane windows, and a properly detailed weather barrier before you spend on stone counters.

The schedule, written out.

Week 0
Feasibility + zoning
Site walk, address-specific zoning pull (LAR1, RM, SF RH-1, etc.), setback + FAR check, easement + utility-locate, soils note. Output: go / no-go memo with realistic budget range.
Week 1–3
Schematic design
Two or three plan options, exterior massing, daylight study, septic / sewer routing, panel-load + HVAC sizing. Output: agreed plan + outline spec.
Week 3–8
Construction documents + Title 24
Stamped architectural, structural calcs, MEP, Title 24 energy report, soils where required. Output: permit-ready set.
Week 8–16
Permit + plan check
City intake, back-and-forth corrections, utility-coordination letters (LADWP, PG&E, EBMUD, SFPUC), school fee + capacity fee assessment, permit issuance.
Week 16–22
Site prep + foundation
Demo, excavation, underground plumbing + electrical, formwork, rebar, pour, foundation inspection.
Week 22–30
Framing + dry-in
Framing, roof sheathing, windows, exterior weather barrier, roofing. Building goes from concrete to lockable shell.
Week 30–38
MEP rough + insulation
Rough electrical, plumbing top-out, ducted heat-pump or mini-split, HERS verification, insulation, drywall.
Week 38–48
Finish + close-out
Cabinets, tile, flooring, paint, fixtures, appliances, exterior hardscape, final inspections, separate-meter release, occupancy.

Materials & assemblies.

Component	Default spec	Why
Wall assembly	2x6 @ 16" o.c. + R-23 batt + ½" ZIP-R + ¾" rainscreen	Continuous insulation closes the thermal bridge that meets Title 24 without crippling the layout.
Roof	R-49 raised-heel truss + radiant barrier sheathing + 30-yr architectural shingle or standing-seam metal	Standing-seam wins on a flat-roof or low-slope detached ADU; shingle is fine on a matched-pitch attached.
Windows	Vinyl or fiberglass, U ≤ 0.30 / SHGC ≤ 0.23, dual-pane low-e	Aluminum frames fail T-24 in almost every CA climate zone.
Heating + cooling	Ducted heat pump (single zone) or ceiling-cassette mini-split	Heat pumps drop ducting complexity and are now cheaper to operate than gas.
Hot water	Heat-pump water heater, 50–65 gal, separate dedicated 240V circuit	Tankless gas is no longer the default — heat pump qualifies for rebates and avoids gas-line trenching.
Subpanel	100A or 125A subfed from main, ground rod at unit, independent disconnect	Independent disconnect is what enables clean future separate-meter conversion.

Hidden costs we flag up front.

Line item	Range	When it hits
Service-panel upgrade	$3K–$12K	main panel is < 200A and you're adding heat pump + EV
Sewer-line replacement	$8K–$28K	pre-1970 clay or cast iron lateral fails camera inspection
Survey + ALTA	$2.5K–$6K	ADU sits within 5 ft of a property line
Tree-protection / removal	$1.5K–$8K	protected tree within drip line of construction
Separate water meter	$5K–$15K	rental and lender requires it
Sprinkler retrofit	$6K–$18K	primary house lacks NFPA 13D and addition triggers it

cheaper alternatives

What we'd consider — and what we wouldn't.

Pre-fab / modular ADU
Lower base price but rarely cheaper all-in once foundation, utility connections, and crane delivery are included; weak on site-specific zoning fit.
Conversion only (no detached)
Faster + cheaper but loses the rental separability and the ROI of a true second dwelling.
Owner-builder
$40K–$80K savings on paper, but most stall in plan-check and lose 6–18 months of carrying cost.

pitfalls — takeover-job patterns

Mistakes to avoid.

Sizing the panel + HVAC for today instead of an electrified future — re-doing it 5 years later costs more than oversizing now
Skipping a sewer-camera before pouring foundation — finding a collapsed lateral after the slab is a $30K+ surprise
Choosing a contractor who has never done a separate-meter coordination — DWP / PG&E paperwork is its own multi-month project
Cheaping out on the weather-resistive barrier — a $400 detail today becomes a $40K mold remediation in year 7

Detached ADU — Los Angeles.

Detached ADU — Bay Area.

In short.

How much does a detached ADU cost in LA in 2026?: $320K–$520K all-in for 600–1,000 sqft. Access, panel, and finish move the number.
Does LA require parking for a new detached ADU?: No within ½ mile of transit — covers most of LA County.
How much does a detached ADU cost in the Bay?: $450K–$720K all-in. SF, Berkeley, and Peninsula coastal cities top the band.
How long does SF DBI take to permit?: 8–12 months in SF. Oakland 4–6. San Jose pre-approved 6–8 weeks.

More we build.

Got a detached adu project in mind?

Send us the address. We'll pull local zoning, setbacks, and detached adu feasibility before you spend on drawings.

Start a project →