ADU Builder in Tumwater, WA

Expand and Maximize Your Tumwater Property Potential

If you own property in Tumwater, you’re sitting on more buildable potential than you might realize. An accessory dwelling unit (ADU) is a self-contained living space added to your existing lot and can serve as a rental, a home for aging parents, an office, or long-term housing. As an ADU builder headquartered on Crites Street SW in Tumwater, Capitol Custom Construction handles the entire process: feasibility review, design, permitting, site preparation, and turn-key construction.

Building an ADU in Tumwater: What’s Different Here?

Washington State passed a landmark ADU law in 2023 (HB 1337) requiring most cities, including Tumwater, to allow at least two ADUs per residential lot. In practice, this means many Tumwater homeowners who previously assumed their lot couldn’t support an ADU should take another look, as local zoning ordinances have significantly relaxed.

That said, the City of Tumwater’s specific municipal code still governs setbacks, lot coverage limits, height maximums, and parking requirements. We pull the actual parcel zoning designation before we design anything, rather than assuming a one-size-fits-all plan will clear city plan review.

Site conditions matter heavily in Tumwater. Parts of town sit close to the Deschutes River and Capitol Lake, where seasonal water tables run high and foundation drainage is paramount. Properties on Tumwater Hill often require engineered retaining or stepped foundation designs. Furthermore, depending on your parcel, you may connect directly to City of Tumwater sewer or require review under Thurston County / LOTT septic regulations. We resolve all of this during the feasibility phase before you commit to final architectural drawings.

The 5-Step Tumwater ADU Process

1. Site Evaluation & Feasibility: We walk your parcel, pull zoning limits, review utilities, and confirm what’s buildable.
2. Design & Permitting: We produce complete 3D architectural and structural plans sized for Tumwater code and submit them directly to City Hall.
3. Site Prep & Foundation: In-house excavation, trenching, drainage, and foundation concrete.
4. Framing & Utilities: Structural framing, plumbing, electrical, roofing, and James Hardie siding.
5. Finishing & Final Occupancy: Drywall, paint, tile, countertops, city inspections, and key handover.