What a garage conversion costs in Seattle in 2026 — by scope. Most 1- and 2-car garage conversions run between $25,000 for a simple bonus room and $200,000+ for a full ADU-style suite with bedroom, bath, kitchenette, and independent HVAC. Pricing below is all-in (labor, materials, garage-door infill); SDCI permits and pre-1978 contingencies are called out separately.
This page is a reference guide, not an interactive calculator — garage conversions vary enough project-to-project (ceiling height, existing slab condition, whether you're tying into main-home HVAC, whether it's a legal ADU) that we quote them directly. For other project types we offer instant estimates: see the basement calculator (closest scope) or the full calculator hub.
Tell us the garage footprint and target scope (bonus room, guest suite, or ADU) and we'll come back with a detailed line-item estimate within 48 hours. No obligation, no sales pressure.
Ranges are all-in for a typical 1-car (~250 sq ft) or 2-car (~450 sq ft) garage in Seattle. Add +12% contingency on homes built before 1978 for asbestos, lead, and knob-and-tube risk.
$12,000-$25,000
Garage door stays in place (with upgraded insulated panels). The space is conditioned and finished but isn't habitable living space by code — great for a gym, workshop, or playroom.
$25,000-$50,000
Garage-door-to-wall infill creates a permanent room. No bath, no kitchen — just a clean conditioned bonus space. Seattle's most common garage conversion.
$55,000-$95,000
Adds a full bath with rough plumbing and a sub-panel if needed. Often used as a guest suite or in-law setup. Triggers SDCI permit and inspection.
$100,000-$200,000+
Legal bedroom with egress, full bath, kitchenette, independent HVAC, soundproofing. Best ROI on rentable space in Seattle's constrained market. Requires SDCI ADU permit.
These are the line items a garage conversion has that a basement or bathroom remodel doesn't.
Seattle garage conversions run $25,000-$50,000 for a bonus room (conditioned, no bath), $55,000-$95,000 for a standard buildout with bath, and $100,000-$200,000+ for a full ADU-style suite. All figures include the garage-door-to-wall infill (~$3-8k within totals). Pre-1978 homes add ~12% contingency.
Remove door + tracks, frame a stud wall matching exterior, install window or patio door, match exterior cladding, patch drywall. Budget $3,000-$8,000. Most Seattle conversions add a 4-ft window so the room doesn't feel cave-like. Add $1,500-$3,000 for a dedicated entry door with covered step.
Almost always yes. Converting garage to habitable space triggers SDCI review — you're adding assessed sq ft. Legal bedroom needs egress window (IRC R310). A full ADU permit is larger: energy-code envelope compliance, soundproofing to main home, potentially separate address. Check /permit-assessment for your specific project.
Yes. A 'conditioned bonus room' with insulated garage door, electrical, HVAC, and finished floor runs $12,000-$25,000. Seattle doesn't treat this as habitable living space (can't be a bedroom, doesn't count toward home sq ft), but it's legal and useful for a gym, workshop, or playroom.
Two paths. Extend main-home ductwork ($1,200-$2,500) if existing HVAC has 500-800 sq ft of spare capacity. Or ductless mini-split ($3,500-$6,500 installed) — dedicated zone, independent temperature control, HOMES-rebate eligible when paired with envelope upgrades. Mini-splits are the default for full ADU conversions.
Not yet — garage conversions vary enough in slab condition, ceiling height, and HVAC tie-in that we price them directly rather than via calculator to avoid quote drift. If you want an instant number for the conditioned-finish portion only, try the basement calculator (~80% scope overlap). For the garage-door infill and other garage-specific items, add $3,000-$8,000 on top. Best path for a firm number: request a quote via the button above — 48-hour response.
