ADU & DADU Construction in Bonney Lake, WA

ADU & DADU Construction in Bonney Lake, WA

Bonney Lake's newer housing stock and larger lots make it one of the strongest candidates for detached ADU construction in Pierce County. I work throughout Sky Island, the Lake Tapps plateau, and the neighborhoods along Highway 410. Most homes here were built between 2000 and 2015 on lots ranging from 7,000 to over 12,000 square feet. That extra yard space means you can build a detached accessory dwelling unit without crowding the main house. I have been building and remodeling in the Pierce County area for over 20 years, and Bonney Lake properties are some of my favorite ADU projects because the lots give me room to design something that actually works.

The most popular ADU project I handle in Bonney Lake is a new detached backyard cottage. These standalone units range from 400 to 800 square feet and cost $180,000 to $400,000 depending on size, foundation type, and finish level. I build on both slab-on-grade and crawl space foundations depending on the site grade and the homeowner's preference. Each unit gets its own full kitchen, bathroom, living area, and bedroom. For homeowners who already have a large attached garage, I also do garage conversions where I partition off a portion of a 3-car garage into a studio apartment with a kitchenette and bathroom. That kind of conversion runs $85,000 to $175,000. Rental rates in the Bonney Lake area run $1,400 to $1,900 per month for a well-finished ADU. See my ADU construction page for a full breakdown of the process.

ADU permits in Bonney Lake go through the City of Bonney Lake Permit Center. The city adopted Ordinance 1737 in June 2025 to comply with Washington's HB 1337, which requires all cities to allow at least 2 ADUs per residential lot. Bonney Lake sets a minimum ADU size of 300 square feet for attached units and 450 square feet for detached units. Stormwater system development charges for ADUs are set at 77% of the standard rate, which helps keep your soft costs down. I handle the full permit package including the site plan, building plans, and utility connection applications. Bonney Lake has specific setback and lot coverage requirements that vary by zone, and I calculate all of that before we start design so there are no surprises at the plan review stage.

If you have a Bonney Lake property with unused yard space, a detached ADU could be the best investment you make this year. Call me at (253) 392-9266 or request a free estimate. I will walk your lot, check setbacks, and give you a fixed-price number for the complete build. Visit my Bonney Lake service area page for more on the work I do in your area.