Garage & Basement ADU Conversions in Clark County, WA
Converting a garage or basement is usually the most affordable way to add an ADU, because the walls, roof, and foundation are already there. You are paying to finish and outfit the space, not to build a structure from the ground up.
We turn that existing shell into a real, permitted home: framing and insulation, a full kitchen and bath, heating and electrical, egress and light, and finishes you would actually want to live in. The result is a unit that works for family or rents on its own.
It is also one of the highest-return upgrades on a property, which is exactly how we think about it. An ADU should pay you back, so we help you scope it to hit the return you are after, not just to fill the space.
What this typically costs
An average garage or basement adu conversion in Clark County runs roughly $45,000 to $105,000+, depending on size and finish. A complete planning range with nothing hidden to add later. Final materials, any structural work, and site conditions are set on a walkthrough, so a detailed estimate can land higher. The real number comes from that walkthrough.
- Good: $90-$120 per square foot. Functional, code-ready unit: efficient kitchen, full bath, durable finishes.
- Better: $120-$160 per square foot. Upgraded kitchen and bath, better flooring, more natural light.
- Best: $160-$210 per square foot. High finish throughout, reworked layout, quality fixtures and cabinetry.
- Premium: $210-$270 per square foot. Premium finishes, custom cabinetry, and design-led details throughout.
Estimate any size: total = the per square foot rate above times the square footage, with a project minimum of $35,000 to $45,000. Try the interactive estimator.
What's included
- A feasibility and zoning check for converting your specific garage or basement
- Framing, insulation, and the systems an existing shell is missing
- A full kitchen and bathroom, heating, and electrical brought to code
- Egress, windows, and light to meet living-space requirements
- Permitting and one accountable team through final inspection
Signs it's time
- A garage or basement that stores clutter more than it earns its space
- A goal of rental income without building a separate structure
- Family who needs a private, self-contained unit on the property
- The most budget-friendly path to a legal ADU
Common questions
Is a garage conversion cheaper than a detached ADU?
Usually, yes. The foundation, walls, and roof already exist, so you are finishing and outfitting rather than building from scratch. That is why conversions typically start around $45,000 versus roughly $140,000 for a detached unit.
Can a converted garage be a legal rental?
Yes, when it is permitted as an ADU and meets code for egress, light, ceiling height, and systems. We handle the permitting and bring the space up to those standards as part of the conversion.
After the conversion, the Proactive Path keeps the new unit and the main home maintained on a schedule, so it holds its value and stays rentable. Explore the 360° Method membership.
Rules & resources
We build to code and to the rules where you live. ADU regulations are set by the state, the county, and your city, and they keep changing. These are the official sources; the first step on any ADU is confirming exactly what applies to your address, which we handle.
- Washington State: ADU law (RCW 36.70A.681, from HB 1337)
- Washington State Dept. of Commerce: Accessory Dwelling Units
- Clark County (unincorporated): ADUs and Cottage Housing
- City of Vancouver: Accessory Dwelling Units
- City of Camas
- City of Washougal
- City of Ridgefield
- City of Battle Ground
Related services
Serving all of Clark County, WA. Call (360) 838-6731 or schedule a consultation.