King County ADU Specialists

Build an ADU in King County
— Done Right.

Get matched with experienced, licensed ADU builders who understand King County zoning, permits, and real costs.

01 Tell us about your property
02 We match you with qualified ADU builders
03 Get expert guidance & pricing options
Request Free Consultation
200+ ADU Permits Approved in King County
100% Licensed & Insured Builders
Free Initial Consultation — No Commitment
12+ Cities Served Across King County

King County Projects

Quality ADUs Across the Region

From detached backyard cottages to garage conversions — we've helped homeowners across Seattle, Bellevue, Redmond, Renton, and beyond.

Detached ADU in King County

Detached Backyard ADU — Bellevue

ADU garage conversion

Garage Conversion — Redmond

King County service area

Serving All of King County

Simple Process

How It Works

01

Tell Us About Your Property

Fill out our quick form. We'll ask about your lot, your goals, and your timeline — takes about 2 minutes.

02

Get Matched With Qualified Builders

We connect you with ADU experts who know King County zoning, permits, and the local market inside and out.

03

Receive Expert Guidance & Pricing

Free consultation to plan your project. Get realistic, itemized estimates from licensed, vetted builders.

Why Choose Us

Built for King County Homeowners

  • Serving Seattle, Bellevue, Redmond, Renton & all of King County
  • Licensed & insured ADU builders — every project, every time
  • Hundreds of ADU permits approved in King County

"King County has made it easier than ever to build an ADU. The right builder makes all the difference — and we know exactly who to call."

— King County ADU Specialists

Free Consultation

Ready to Build Your ADU?

Tell us about your property and we'll connect you with King County's top-rated ADU builders — no obligation, no pressure.

No commitment required Response within 24 hours King County licensed builders

Your Property Information

Resources

King County ADU Guide

Most single-family properties in King County can build an ADU, but eligibility depends on lot size, zoning, and existing structures. Here's what you need to know before you start.

Can I Build an ADU?

Most single-family properties qualify. Eligibility depends on lot size, zoning, and existing structures. We help you understand your property's potential before you commit to anything.

Types of ADUs

  • Detached ADU: A separate structure in your backyard
  • Garage Conversion: Turn your garage into a livable unit
  • Basement ADU: Convert basement space into an apartment
  • Not sure yet: We help you explore all options

Permits & Process

Permits are required for every ADU. Typical steps include site evaluation, permit submission, and city inspection. Our builders know the process and can guide you every step of the way.

Typical Costs

Backyard cottages range from $150–$400 per square foot in King County. Costs vary based on size, type, and location. We connect you with builders who give realistic, itemized estimates.

Common Questions

Frequently Asked Questions

Do I need a permit for a basement ADU in Seattle?

Yes, all ADUs require a building permit. Our builders handle the permit process and know exactly what King County reviewers look for.

How long does it take to build an ADU?

Typically 6–12 months depending on complexity, permit timelines, and the type of ADU. Permitting alone can take 2–4 months in some jurisdictions.

Can I rent my ADU immediately?

You must follow King County occupancy and rental rules. Once your certificate of occupancy is issued, rental is typically permitted right away.

How much does an ADU cost?

Costs vary widely by type and size. We connect you with builders who provide accurate, itemized estimates based on your specific property and goals.

Start Your ADU Project Today

Free consultation. No commitment. King County's top builders ready to help.

Get Free Estimate