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

A garage conversion is usually the lowest-cost path to an ADU in Portland — $70,000-$160,000, versus $150,000-$300,000 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 $150,000-$300,000 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 $1,500-$2,500. A converted unit rents for about $1,400-$1,900/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: By-right approval (no variance needed) The review timeline is 30-45 days, with plan check: 1-2 weeks. Pre-approved plans: Extensive pre-approved library available.

Confirm eligibility — ADUs are allowed in All residential zones.
Prepare conversion plans — layout, egress windows, insulation, ventilation, smoke/CO detectors, plus a kitchen and bathroom.
Submit for plan check — 1-2 weeks.
Pull permits and build — fees run $1,500-$2,500; then framing, electrical, plumbing, and final inspection.

Parking Rules for a Garage Conversion

Optional 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 800 sq ft 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.

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Portland Garage Conversion FAQ

How much does a garage conversion cost in Portland?

A garage conversion in Portland typically costs $70,000-$160,000 — well below the $150,000-$300,000 cost of a new detached ADU, because the foundation, walls, and roof already exist. Budget separately for permit fees ($1,500-$2,500) and any electrical or utility upgrades the conversion triggers.

Do I need a permit to convert a garage in Portland?

Yes. Converting a garage to a living unit in Portland requires building permits even if the exterior stays the same — the work has to meet code for insulation, egress, ventilation, electrical, and a kitchen/bathroom. The ADU permit timeline is 30-45 days, and the process is: By-right approval (no variance needed)

Do I have to replace the parking if I convert my garage in Portland?

Optional Garage conversions sometimes trigger different parking rules than new detached ADUs, so confirm replacement-parking requirements with Portland before you start.

How long does a garage conversion take in Portland?

Plan on 30-45 days for permit review (1-2 weeks for plan check), then construction. A garage conversion is usually faster to build than a ground-up ADU because the structure already exists.

Can I convert an attached garage into a JADU in Portland?

If the garage is attached to the house, yes — a junior ADU (JADU), capped at 800 sq ft, can be carved out of the existing footprint, which includes an attached garage. JADUs are cheaper but may share sanitation with the main home.

Compare your options: see the full Portland ADU rules, estimate your build with the Portland ADU cost calculator, or read the general garage conversion guide.

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