Accessory Dwelling Unit (ADU) Construction in Seattle, WA — Costs $91,330 to $532,758
What does accessory dwelling unit (adu) construction cost in Seattle? Average $228,325, ranging $91,330–$532,758. Labor runs $49.93/hr locally — 52% above the national average. Free breakdown with material + labor split.
Seattle, WA Market
+52% vs nationalLabor Rate
$49.93/hr
Material Index
138
Avg Permit Cost
$2,240
Median Home Price
$616,441
As one of the largest metros in Washington, Seattle has a competitive contractor market with hundreds of licensed professionals. This typically gives homeowners more leverage on pricing, though high demand for renovations can offset that advantage. At 52% above the national average, Seattle is one of the more expensive markets for home improvement — driven primarily by above-average labor rates in the region. With a median home price of $616,441, this accessory dwelling unit (adu) construction represents just 37.0% of typical home value — a relatively small investment that can significantly boost curb appeal or functionality.
Low Estimate
$91,330
National: $60,000
Mid-Range
$228,325
National: $150,000
High End
$532,758
National: $350,000
Per Sq Ft
$381
National: $250
Accessory Dwelling Unit (ADU) Construction Cost Calculator for Seattle
Adjusted for Seattle's labor rate ($49.93/hr) and material costs (index 138).
Mid-grade materials, good quality fixtures, standard options.
Estimated Total in Seattle
$228,325
Based on 200 sq ft at mid quality, adjusted for Seattle market rates.
Local Cost Breakdown
At Seattle's average rate of $49.93/hr (66% above national avg)
Material cost index 138 (38% above national baseline of 100)
Accessory Dwelling Unit (ADU) Construction vs. Home Value in Seattle
| Metric | Seattle | National Avg |
|---|---|---|
| Accessory Dwelling Unit (ADU) Construction (Mid-Range) | $228,325 | $150,000 |
| Median Home Price | $616,441 | $350,000 |
| Project as % of Home Value | 37.0% | 42.9% |
| Estimated ROI | 80% | 80% |
| Median Household Income | $106,476 | $75,000 |
What Affects the Price in Seattle
- 1Local labor rates ($49.93/hr in Seattle)
- 2Material cost index (138 vs national 100)
- 3Attached vs detached
- 4Size and bedroom count
- 5Kitchen and bath quality
- 6Local ADU regulations
Popular Upgrades
- Full kitchen
- Separate entrance
- Solar panels for energy independence
Other Projects in Seattle, WA
Second Story Addition
$304,433
Room Addition
$136,995
Swimming Pool Installation
$97,093
Garage Addition
$83,719
Home Addition
$120,636
Inground Swimming Pool
$96,169
Attic Conversion
$84,501
Swimming Pool Construction
$76,819
Accessory Dwelling Unit (ADU) Construction in Other Washington Cities
Planning a Accessory Dwelling Unit (ADU) Construction in Seattle
Building permits are typically required for a accessory dwelling unit (adu) construction in Seattle. The average permit fee in this area is $2,240, though costs vary based on project scope. Permit fees in this market are above average — factor them into your total budget. Plan for 6-18 months from start to finish.
A accessory dwelling unit (adu) construction is a complex project best left to licensed professionals. In Seattle, skilled contractors charge an average of $49.93/hr, and the specialized nature of this work means cutting corners on labor can lead to costly rework.
With a median household income of $106,476, many Seattle residents can budget for this project through savings. The mid-range cost of $228,325 represents 214% of the typical household's annual income.
Accessory Dwelling Unit (ADU) Construction — National Guide
See the full national cost guide with DIY tips, cost factors, and ROI analysis.
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