Northwest ADU Builders of Mill Creek

Northwest ADU is a full-service ADU design, permitting, and construction company specializing in accessory dwelling units throughout Washington. The company focuses exclusively on ADU projects and manages the process from feasibility and site evaluation through design, permitting, construction, final inspection, and handover.

An accessory dwelling unit (ADU) — also known as a granny flat, in-law suite, backyard cottage, casita, or secondary dwelling unit — is an independent living space located on the same property as a primary residence.

ADU Services

1. Detached ADUs: Northwest ADU designs and builds standalone backyard homes suitable for rental income, guest accommodation, multigenerational living, home offices, or future downsizing.
2. Garage Conversions: Existing garages can be converted into fully functional, code-compliant residential living spaces.
3. Basement Conversions: Underused basement areas can be transformed into comfortable apartment-style living spaces where local regulations permit.
4. Build-Ready ADU Plans: The company offers pre-designed, permit-ready plans intended to streamline the design and approval process.

What Northwest ADU Offers Beyond Construction

Northwest ADU manages the ADU process through a structured, start-to-finish approach. Its feasibility stage evaluates lot size, zoning, setbacks, height limits, utility capacity, stormwater requirements, access, and grading conditions before design begins.

The design and planning phase includes floor plans, budgeting, and engineering, followed by permit submission and coordination with local authorities. Construction then proceeds through final inspection and handover.

For detached ADUs, the company offers build-ready configurations ranging from approximately 400–600 square feet for studios, 600–800 square feet for one-bedroom units, and 800–1,000+ square feet for two-bedroom units, depending on local requirements and site conditions.

Northwest ADU emphasizes transparent pricing, realistic timelines, permitting expertise, structured project management, and communication throughout the project.