How much does adu construction cost in 2026?

Most homeowners pay between $150,000 and $300,000, with a national average near $225,000. Small, simple jobs land at the low end; large or premium-material jobs run well above the high end.

What is the cost per square foot?

Installed pricing usually runs $250.00 to $500.00 per square foot, including labor and materials. Expensive metros can run 15–45% higher than that range.

What drives the price up the most?

Scope and access. Larger quantities lower your per-square foot price, but difficult access, demolition of existing work, structural repairs found mid-job, premium materials and rush scheduling each add 8–30%.

Permits are typically required when the work changes structure or ties into electrical, plumbing, gas or mechanical systems. Budget $75–$600 in most cities and confirm whether your contractor pulls it — unpermitted work can block a future home sale.

How long does the job take?

Most residential projects of this type finish in one to five working days once materials are on site. Custom orders, inspections and weather are the usual causes of delay.

How many quotes should I get?

Three. Bids on the same scope commonly vary 20–40%, and the middle bid with the strongest warranty and references is usually the best value — the cheapest bid often excludes prep, disposal or permits.

When is the cheapest time to book?

Off-season and shoulder months. Booking outside the spring–summer rush, and staying flexible on start dates, commonly saves 5–15% because crews are filling calendar gaps.

Yes. Contractor financing, a home equity line, or a 0% promotional card are all common. Compare the total interest cost against paying cash — promotional financing is sometimes priced into a higher bid.

How do I avoid getting overcharged?

Get the scope in writing with materials by brand and model, quantities, exclusions, permit responsibility, payment schedule and warranty. Never pay more than one third up front, and never pay in full before the final inspection.

How much does an ADU cost to build?

Site-built ADUs generally run $250–$500 per square foot, so $150,000–$300,000 for 600 square feet. Garage conversions cost far less.

Do ADUs pay for themselves?

In high-rent metros many cash-flow in 8–15 years, and appraisers commonly credit meaningful value at resale.

How long does it take?

Six to eighteen months from design through final inspection, with permitting the biggest variable.

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Construction

How much does adu construction cost?

ADU Construction costs $150,000 to $300,000 for a typical project, averaging about $225,000. Installed pricing usually runs $250.00 to $500.00 per square foot, and scope, materials, access and local labor rates explain nearly all of the variation.

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National average

$225,000

Typical low

$150,000

Typical high

$300,000

Per square foot

$250 – $500

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ADU size (sq ft)600 square feet

Quality / material level

Site access

Removal / prep work

Timing

Region

Estimated project cost

$152,404 – $208,941

Most homeowners pay around $180,672

Compare quality / material level

Cost by material

Installed pricing per square foot.

Option	Installed cost	Pros	Cons
Prefab studio ADU	$233 – $319	—	—
Site-built 1-bedroom	$319 – $420	—	—
Site-built 2-bedroom	$420 – $544	—	—
Custom high-end ADU	$544 – $750	—	—

ADU Construction cost by project size

Typical installed pricing before local adjustments.

Project size	Budget	Average	Premium
300 square foots	$75,000	$112,500	$150,000
600 square foots	$150,000	$225,000	$300,000
900 square foots	$225,000	$337,500	$450,000
1200 square foots	$300,000	$450,000	$600,000

ADU Construction cost by material or quality level

Option	Price range	Best for
Prefab studio ADU	$232.50 – $318.75 / square foot	Lowest upfront cost, shortest lifespan
Site-built 1-bedroom	$318.75 – $420.00 / square foot	Best overall value for most homes
Site-built 2-bedroom	$420.00 – $543.75 / square foot	Longer warranty and better finish
Custom high-end ADU	$543.75 – $750.00 / square foot	Top-tier materials and custom detailing

Where the money goes

A typical project budget, broken down by line item.

Labor0.45% · $1,013
Materials0.38% · $855
Permits & inspections0.05% · $113
Overhead & profit0.12% · $270

Cost by region

Labor markets move the number more than any other single factor.

Northeast

$172,500 – $345,000

+15% vs. national average

West

$177,000 – $354,000

+18% vs. national average

Midwest

$144,000 – $288,000

-4% vs. national average

South

$141,000 – $282,000

-6% vs. national average

Common add-ons

Line items that show up on most quotes but rarely in the headline price.

Utility connections

$8,000 – $30,000

Site work and foundation

$15,000 – $60,000

Design and permits

$8,000 – $30,000

Impact fees

$2,000 – $20,000

DIY vs. hiring a pro

Hire a pro

$150,000 – $300,000

Do it yourself

$67,500 – $165,000

DIY saves labor but not materials, permits or rework. Only take it on if the job does not require a licensed trade or inspection.

Ways to save

Practical levers that lower the bill without cutting quality.

Use pre-approved ADU plans where your city offers them — saves months and design fees.
Detach only if required; attached and conversion ADUs cost far less.
Collect three written bids on an identical scope — spreads of 20–40% are normal.
Book in the off-season and stay flexible on the start date to save 5–15%.
Bundle nearby work into one mobilization so you only pay setup and travel once.
Ask what the contractor would change to cut 10% without hurting durability.

Questions to ask your contractor

01Are you licensed and insured in my city, and can I see the certificate?
02Is this a fixed-price bid or an estimate that can change?
03What exactly is excluded from the quote?
04Who pulls the permit and who schedules inspections?
05What is the written workmanship warranty and how long does it last?
06What is the payment schedule, and how much is due up front?
07How long will the work take, and what could delay it?

Frequently asked questions

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ADU Construction cost by city

Local labor rates, permits and climate change the number. Pick your city for prices near you.

ADU Construction cost in Los Angeles, CA

$186,000 – $372,000

ADU Construction cost in San Diego, CA

$177,000 – $354,000

ADU Construction cost in San Jose, CA

$207,000 – $414,000

ADU Construction cost in San Francisco, CA

$217,500 – $435,000

ADU Construction cost in Oakland, CA

$198,000 – $396,000

ADU Construction cost in Sacramento, CA

$162,000 – $324,000

ADU Construction cost in Fresno, CA

$147,000 – $294,000

ADU Construction cost in Long Beach, CA

$183,000 – $366,000

ADU Construction cost in Anaheim, CA

$180,000 – $360,000

ADU Construction cost in Santa Ana, CA

$178,500 – $357,000

ADU Construction cost in Irvine, CA

$189,000 – $378,000

ADU Construction cost in Riverside, CA

$159,000 – $318,000

ADU Construction cost in San Bernardino, CA

$154,500 – $309,000

ADU Construction cost in Bakersfield, CA

$145,500 – $291,000

ADU Construction cost in Stockton, CA

$153,000 – $306,000

ADU Construction cost in Modesto, CA

$150,000 – $300,000

ADU Construction cost in Chula Vista, CA

$172,500 – $345,000

ADU Construction cost in Fremont, CA

$202,500 – $405,000

ADU Construction cost in Pasadena, CA

$192,000 – $384,000

ADU Construction cost in Glendale, CA

$187,500 – $375,000

ADU Construction cost in Santa Clarita, CA

$174,000 – $348,000

ADU Construction cost in Torrance, CA

$184,500 – $369,000

ADU Construction cost in Oxnard, CA

$171,000 – $342,000

ADU Construction cost in San Mateo, CA

$210,000 – $420,000

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