Garage Conversion in Portland, OR: Cost, Permits & Rules (2026)

A garage conversion is usually the lowest-cost path to an ADU in Portland — $70,000-$160,000, versus $180,000-$280,000 for a new detached build — because the shell already exists.

Garage Conversion Cost in Portland

Converting an existing garage in Portland runs $70,000-$160,000. That's well under the $180,000-$280,000 typical cost of a ground-up detached ADU, because you're reusing the foundation, walls, and roof. The biggest variables are whether the slab and framing are sound, what utility/electrical upgrades are needed, and your finish level. Permit fees add Building permit and plan-review fees are valuation-based under the Building and Other Permits Fee Schedule effective July 10, 2026 (no flat ADU fee); trade permits are separate. SDCs: Parks $7,941 (under 700 sq ft) or $11,878, Transportation $3,421, waived with the 10-year no-STR covenant. A converted unit rents for about $1,400-$1,700/mo (1BR) in Portland.

The Portland Garage Conversion Permit Process

A garage-to-ADU conversion in Portland needs building permits even if the exterior is unchanged. Approval process: Ministerial building permit through Portland Permitting & Development (PP&D); no land-use review when the unit meets Chapter 33.205 and the base-zone accessory-structure standards. Steps: 1) check permit history, zoning, flood/slope hazard and tree rules on PortlandMaps; 2) optional free 15-minute appointments with a planner, building-code reviewer, water, sewer and transportation staff; 3) submit the building permit, site plan, architectural and structural plans, trade permits and the Residential SDC form as a single PDF on Development Hub PDX (write 'Pre-Approved ADU' if using a city plan set); 4) checksheet correction rounds; 5) pay fees and pick up the permit; 6) inspections booked on DevHub or 503-823-7000. Electrical work must be done by a licensed contractor even on an owner-built ADU. A unit that misses a zoning standard needs a discretionary Adjustment Review under 33.805 The review timeline is The city publishes no fixed ADU review time; plan review runs on DevHub with checksheet correction rounds, so allow for at least one. If a zoning standard is missed, the Adjustment Review alone takes about 8-10 weeks (city ADU zoning page, 2026), with plan check: Electronic single-PDF plan review on Development Hub PDX; paper plans by appointment only. New detached ADUs are reviewed under the Oregon Residential Specialty Code, conversions under the city's ADU Code Guide. A lot with 20% or steeper slope or in a landslide area needs a geotechnical report; a garage in a flood hazard area may not be convertible; trees with trunks over 12 in need protection measures. Pre-approved plans: Yes. The city offers 4 free pre-approved detached ADU plan sets (gable or shed roof, on a concrete slab or a wood-framed crawl space), adapted from the City of Eugene's plans. They are not suited to every lot: the shed-roof slab design exceeds the size allowed inside a side or rear setback, and the bathroom does not meet the visitability standard required when a lot has two ADUs. Truss packages can be a deferred submittal.

1. Confirm eligibility — ADUs are allowed in Every residential zone (RF, R20, R10, R7, R5, R2.5 and the multi-dwelling RM zones) plus the commercial mixed-use and Central Employment (EX) zones, on a lot with a house, attached house, manufactured home or duplex (33.205.020). Not allowed with a triplex, fourplex, cottage cluster or multi-dwelling building. Check your base zone on the Portland Zoning App.
2. Prepare conversion plans — layout, egress windows, insulation, ventilation, smoke/CO detectors, plus a kitchen and bathroom.
3. Submit for plan check — Electronic single-PDF plan review on Development Hub PDX; paper plans by appointment only. New detached ADUs are reviewed under the Oregon Residential Specialty Code, conversions under the city's ADU Code Guide. A lot with 20% or steeper slope or in a landslide area needs a geotechnical report; a garage in a flood hazard area may not be convertible; trees with trunks over 12 in need protection measures.
4. Pull permits and build — fees run Building permit and plan-review fees are valuation-based under the Building and Other Permits Fee Schedule effective July 10, 2026 (no flat ADU fee); trade permits are separate. SDCs: Parks $7,941 (under 700 sq ft) or $11,878, Transportation $3,421, waived with the 10-year no-STR covenant; then framing, electrical, plumbing, and final inspection.

Parking Rules for a Garage Conversion

None. No additional on-site parking is required for an ADU (city ADU zoning page, 2026), and ORS 197A.425(1)(b)(B) bars Oregon cities from requiring it; converting a garage does not require replacement parking Garage conversions sometimes trigger different parking rules than new detached ADUs, so confirm replacement-parking requirements with Portland before you start. Owner-occupancy is not required, so you can rent the converted unit out.

The JADU Option for an Attached Garage

If your garage is attached to the house, you can convert it into a junior ADU (JADU) — capped at N/A (Oregon and Portland have no junior ADU category; a unit inside the house is simply an ADU under the same 800 sq ft / 75% cap) and built within the existing walls. JADUs are cheaper and faster to permit than a full ADU, though they may share sanitation with the main home. A full ADU gives you more size and a separate unit; a JADU is the budget route.

Portland Garage Conversion FAQ