How much does adu construction cost in Renton, WA?

Most Renton homeowners spend between $180,000 – $360,000 on adu construction, with an average around $270,000. Local labor prices 20% above the national average, so Renton quotes tend to land at the higher end of national ranges.

Why is adu construction more or less expensive in Renton than elsewhere?

Renton follows the King County labor market. Rain and moss make maintenance a recurring cost.

Do I need a permit for adu construction in Renton, Washington?

City permits with critical-areas review in some neighborhoods. Always confirm current requirements with the local building department before signing a contract, and make sure the permit is pulled by your licensed contractor.

How many quotes should I get in Renton?

Get at least three written quotes from licensed, insured Washington contractors. Comparing line items — not just the bottom line — is the fastest way to spot an inflated bid in the Seattle market.

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.

Home/Cost guides/ADU Construction/Renton, WA

Seattle · Washington

ADU Construction cost in Renton, WA

Renton homeowners typically pay $180,000 – $360,000 for adu construction. Local labor and materials price 20% above the national average.

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Renton average

$270,000

Typical low

$180,000

Typical high

$360,000

Per square foot

$300 – $600

Sample ZIP

98055

What drives Renton pricing

Local labor

Renton follows the King County labor market.

Permits & code

City permits with critical-areas review in some neighborhoods.

Climate & conditions

Rain and moss make maintenance a recurring cost.

Instant cost calculator

Adjust the inputs to see live pricing

ADU size (sq ft)600 square feet

Quality / material level

Site access

Removal / prep work

Timing

Estimated project cost

$159,600 – $219,450

Most homeowners pay around $189,525

Compare quality / material level

Cost by material in Renton

Installed Renton pricing per square foot.

Option	Installed cost	Pros	Cons
Prefab studio ADU	$280 – $385	—	—
Site-built 1-bedroom	$385 – $505	—	—
Site-built 2-bedroom	$505 – $655	—	—
Custom high-end ADU	$655 – $900	—	—

Where the money goes in Renton

A typical $270,000 Renton project, broken down by line item.

Labor0.45% · $1,215
Materials0.38% · $1,026
Permits & inspections0.05% · $135
Overhead & profit0.12% · $324

Common add-ons

Extras that show up on Renton quotes but rarely in the headline price.

Utility connections

$9,600 – $36,000

Site work and foundation

$18,000 – $72,000

Design and permits

$9,600 – $36,000

Impact fees

$2,400 – $24,000

Ways to save in Renton

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.

Renton FAQs

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More Renton research

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ADU Construction cost near Renton

ADU Construction cost in Seattle, WA

$192,000 – $384,000

ADU Construction cost in Bellevue, WA

$198,000 – $396,000

ADU Construction cost in Tacoma, WA

$172,500 – $345,000

ADU Construction cost in Everett, WA

$177,000 – $354,000

ADU Construction cost in Kent, WA

$178,500 – $357,000

More Washington cities

Spokane Vancouver Olympia

Other project costs in Renton

Fence Installation in Renton

$1,800 – $4,800

Roof Replacement in Renton

$10,200 – $40,800

Kitchen Remodel in Renton

$21,600 – $114,000

HVAC Replacement in Renton

$6,600 – $21,600

Deck Building in Renton

$5,280 – $14,400

Window Replacement in Renton

$540 – $1,800

See every Renton cost guide