Build an ADU in King County — Done Right
Get matched with experienced, licensed ADU builders who understand King County zoning, permits, and costs.
1. Tell us about your property
2. We match you with qualified ADU builders
3. Get expert guidance + pricing options
Why Work With Us
- ✅ Serving Seattle, Bellevue, Redmond, Renton & all King County
- ✅ Licensed & insured ADU builders
- ✅ Hundreds of ADU permits approved in King County
How It Works
- Tell us about your property: Fill out our quick form above.
- Get matched with qualified builders: We connect you with ADU experts in King County.
- Receive expert guidance & pricing: Free consultation to plan your ADU project.
King County ADU Guide
Can I Build an ADU in King County?
Most single-family properties in King County can build an ADU, but eligibility depends on lot size, zoning, and existing structures. We help you understand your property’s potential before you start.
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.
King County ADU Permits
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 ADU Costs
Costs vary based on size, type, and location. On average, backyard cottages range from $150–$400 per square foot in King County. We help you get realistic estimates from qualified builders.
Frequently Asked Questions
- Do I need a permit for a basement ADU in Seattle? Yes, all ADUs require a building permit.
- How long does it take to build an ADU? Typically 6–12 months depending on complexity.
- Can I rent my ADU immediately? You must follow King County occupancy and rental rules.
- How much does an ADU cost? Costs vary; we connect you with builders who can give accurate estimates.