Cost guide · Updated 2026-04-01

How much an ADU actually costs in California (2026).

Detached new-build ADUs run $250–$385/sqft in LA and $310–$485/sqft in the Bay. Garage conversions and JADUs come in lower — but only when the existing shell passes inspection.

Installed cost bands

$/sqft of finished area for these scopes — LA versus Bay Area, side by side.

Scope	Los Angeles	Bay Area
Detached new-build ADU	$250–$385 Driven by foundation type, site access, finish tier.	$310–$485 Bay labor premium; hillside lots push the high end.
Attached ADU / addition	$220–$340 Tie-in to existing structure adds soft cost.	$285–$430 Roof and shear-wall integration are budget drivers.
Garage conversion ADU	$145–$230 Only pencils if slab + walls are sound.	$180–$290 Older garages often need full slab tear-out.
JADU (within main house)	$125–$195 Lowest entry point — limited to 500 sqft.	$160–$245 Plumbing fixture relocation is the swing item.

What drives the spread

1.
Foundation type
A continuous footing on flat dirt is the baseline. Pier-and-grade-beam on a hillside, or a structural slab over expansive clay, can add 15–30% to the foundation line alone.
2.
Site access + staging
If the only path to the rear yard is a 36-inch gate, every yard of concrete and stick of lumber is hand-carried. Budget another $8–14K versus a job with truck access.
3.
Finish tier
Builder-grade IKEA-equivalent vs. semi-custom cabinets vs. quartz-everywhere swings $/sqft more than any other single choice. Lock the spec before you sign.
4.
Utility upgrades
A new ADU usually triggers a sub-panel; a 60+ year-old service often forces a 200A upgrade. Sewer lateral compliance, water meter upsize, and PG&E queues are the schedule killers.
5.
Code cycle
The 2025 Title 24 cycle (effective Jan 1, 2026) raised the bar on envelope U-values, balanced ventilation, and EV-ready wiring. Budget 3–6% above 2024 numbers for the same scope.

Soft costs to add on top

The hard-cost bands above exclude these. Forgetting them is the most common reason a budget runs 20% over.

Line item	% of hard cost
Design + engineering (architectural, structural, Title 24) Higher end for hillside, custom, or historic-overlay parcels.	6–12%
Permits + plan check (LADBS / SF DBI / etc.) Add school fees ($4–6/sqft for ADUs > 750 sqft).	2–5%
Utility upgrades (panel, sewer lateral, water meter) Pre-1980 homes routinely hit the top of this range.	3–8%
Survey + soils report Required on hillside and parcels with fault-zone proximity.	0.5–2%
Owner contingency Skip this and the next discovery becomes a change-order argument.	8–15%

Los Angeles — burdened hourly rates

Includes payroll burden + small-tool allocation. Excludes overhead & profit.

Journeyman carpenter: $62–$92/hr
Journeyman electrician: $78–$118/hr
Journeyman plumber: $82–$125/hr
General laborer: $38–$56/hr

Bay Area — burdened hourly rates

Includes payroll burden + small-tool allocation. Excludes overhead & profit.

Journeyman carpenter: $78–$118/hr
Journeyman electrician: $95–$145/hr
Journeyman plumber: $98–$150/hr
General laborer: $48–$72/hr

Field calculator

Run your scope through the ADU calculator

Inputs match the bands on this page — same data, your scope.

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What this is based on

1.
California ADU statute (Gov. Code §65852.2) caps impact fees and requires ministerial review for compliant units.
California HCD · view source
2.
ADU Handbook (2025 update) sets the minimum allowances every jurisdiction must honor.
California HCD · view source
3.
2022 Energy Code requirements remain in force until the 2025 cycle takes effect Jan 1, 2026.
California Energy Commission · view source
4.
NAHB construction cost surveys confirm 60–65% of single-family build cost flows to labor + materials.
National Association of Home Builders · view source

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