Go Far®The cheapest square footage you’ll ever add
A garage conversion starts with the three most expensive parts of any project already built: foundation, roof, and walls. That is why converting a garage costs a fraction of building an addition — you are finishing space, not constructing it. For homeowners across Lynnwood, Seattle, and Snohomish & King County who need one more bedroom, an office, or rental income, the garage is usually the first place worth looking.
What garage conversions cost
- Conditioned room — insulation, drywall, flooring, heat, and the garage-door wall framed in and sided to match. Commonly lands in the $30,000–$60,000 range and turns a cold shell into a real bedroom, office, or family room.
- Room plus full bath — everything above plus a full bathroom plumbed to the main stack. Typically $60,000–$100,000, and the most popular tier for guest suites and multigenerational setups.
- Full ADU — legal bedroom with egress, full bath, kitchenette, separate entrance, and independent heating. Generally $100,000–$200,000+ depending on the garage, utilities, and finishes — still well below what a new-build backyard cottage costs, because the structure exists.
What makes or breaks the budget
Five things move a conversion budget more than everything else combined. The slab: garage floors slope and sit lower than the house, and skipping moisture mitigation is the number-one reason converted garages feel damp — budget for a vapor barrier and a leveled or sleeper floor. The garage-door wall: framing, insulating, and matching your siding so the conversion doesn’t announce itself from the street. Ceiling height: most garages clear the bar; older ones sometimes don’t. Egress: a legal bedroom needs a proper egress window. And utilities: extending heat is simple with a mini-split; adding a bathroom or kitchenette is where trenching and panel capacity enter the conversation. Homes built before 1978 should carry a contingency for what opens up when the walls do.
Permits: yes, you need one
Converting a garage to habitable space requires a building permit everywhere we work — and that is a good thing, because the permit is what makes the square footage count at appraisal and sale. Washington’s 2023 ADU law also removed many of the old barriers to converting garages into dwelling units, including the parking-replacement rules that used to stop these projects before they started. Our ADU & DADU rules guide covers what applies in Lynnwood and Snohomish County, and our permit guide covers the process itself. As your general contractor, we handle the paperwork.
Conversion, DADU, or addition?
The garage conversion is the value play: least new construction, fastest timeline, lowest cost per square foot. A ground-up DADU costs more but gives you a purpose-built, fully separate home that rents at the top of the market. A home addition keeps everything under one roof and one thermostat. The right answer depends on your lot, your garage’s bones, and what the space needs to do — which is exactly what a walk-through settles in an hour.
Quick answers
Do I need a permit to convert my garage in Washington?
Yes. Turning a garage into habitable space — a bedroom, office, family room, or ADU — requires a building permit, and usually electrical and mechanical permits too. Unpermitted conversions create real problems at appraisal and resale, and bringing them up to code later costs more than permitting properly the first time.
How much does a garage conversion cost in the Seattle area?
A straightforward conversion to a conditioned room commonly runs in the $30,000–$60,000 range. Adding a full bathroom typically brings projects into the $60,000–$100,000 range, and a complete, legally rentable ADU with a kitchenette and separate entrance generally lands between $100,000 and $200,000+ depending on the garage and finish level.
Can my detached garage become a DADU?
Often, yes. Washington's ADU-friendly state law requires most cities in urban growth areas to allow accessory dwelling units, and a structurally sound detached garage can be a head start on a backyard cottage. Foundation condition, ceiling height, and utility routing decide whether converting beats rebuilding.
Will a garage conversion hurt my home's resale value?
A permitted, well-built conversion that adds a bedroom, office, or rentable ADU usually adds more value than covered parking is worth in this market — especially where lots still have driveway parking. The projects that hurt value are the unpermitted ones with tell-tale sloped floors and a walled-in garage door.
See what your garage could be
Go Far Construction converts garages, builds ADUs and DADUs, and handles every trade in between across Lynnwood, Seattle, and Snohomish & King County. A free, no-obligation estimate covers your garage’s condition, the permit path, and a real budget range — request yours here.