ADU Builders in Seattle & Snohomish County
Custom Accessory Dwelling Unit (ADU) & DADU Construction
Build a fully permitted ADU, DADU, or backyard cottage with a trusted design-build contractor. From feasibility and permits to final construction, we handle everything.
- Fully Permitted ADUs in Washington State
- Built Green™ Certified Builder
- Design-Build ADU Experts
- Transparent Timeline & Pricing
What Is an ADU
(Accessory Dwelling Unit)?
An ADU is a secondary living space built on your property. In Washington State, ADUs and DADUs are commonly for:
- Rental income opportunities
- Multigenerational living
- Guest houses or home offices
- Increasing long-term property value
Whether you’re early in research or ready to build, our team helps you navigate zoning, design, and construction.
How Much Does an ADU Cost in Washington?
ADU costs vary depending on size, design, and site conditions. Here are typical ranges:
- Detached ADU (DADU): $150,000 – $350,000+
- Garage Conversion ADU: $80,000 – $180,000
- Attached ADU: $100,000 – $250,000
We provide transparent estimates and help you understand what’s possible based on your property and budget
Why Choose Us as Your ADU Contractor?
- Licensed, Bonded & Insured ADU Builders
- Built Green™ Certified Construction
- Full Design-Build Team (No Hand-Offs)
- Transparent Communication with BuilderTrend
- Family-First, Client-Focused Approach
Recent ADU & DADU Projects
See how we transform underutilized spaces into functional, high-quality living environments.
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Serving Seattle & Surrounding Areas
We build ADUs across:
- Seattle
- Lynnwood
- Edmonds
- Kirkland
- Bellevue
- Bothell
- Woodinville
Meet the Team
Our team at MacCoy Home Solutions consists of dedicated professionals committed to delivering exceptional results and customer service.
Aaron MacCoy
Owner
Marie MacCoy
Owner
Bill Hurley
Sales Coordinator & Safety Manager
Kyle Olson
Project Manager
Ariadna Delgado-Trahen
Office Assistant
Derek Collins
Project Manager
Harold Stjern
Field Supervisor
Steven White
Lead Carpenter
Donny Arndt
Lead Carpenter
Jordan Behrens
Carpenter
Frequently Asked Questions
Are ADUs legal in Lynnwood?
Yes. With the right permits, ADUs and DADUs are allowed in most residential zones.
How much does an ADU cost in Lynnwood?
Costs vary based on design, utilities, and site conditions. We provide transparent estimates after assessment.
Can ADUs be used as rentals?
Yes—many homeowners build ADUs for long-term rental income.
Do ADUs increase property value?
Often significantly, especially when professionally designed and built.
Ready to Build Your ADU?
Work with a trusted ADU builder who handles everything—from concept to completion.