Can I turn my garage into an ADU in Portland?
Usually. As of October 2026, Portland lists converting an existing accessory structure, and converting part of the house, among the ways to create an ADU. A detached garage falls under the first path; an attached garage under the second.
Do I need to replace the parking?
Not for the ADU. Oregon law (ORS 197A.425) says a city's ADU siting and design rules cannot require new off-street parking, and Portland states that no extra on-site parking is required for an ADU. See our parking guide.
How big can the conversion be?
The usual cap applies: 800 sq ft or 75% of the house's living area, whichever is smaller. Garage area does not count as living area of the house, so a large garage does not raise the cap. Most single and double garages fall well under 800 sq ft anyway.
What work does a garage usually need?
A garage was built for cars and storage, so the conversion is mostly about making it safe and comfortable to live in:
- Checking the slab and footings, and adding a vapor barrier and insulated floor.
- Insulating walls and roof to Oregon's residential energy code.
- Framing in the garage door opening with wall, windows or an entry door.
- Fire separation where the garage sits close to the house or a property line.
- An electrical load check, often with a new subpanel or service upgrade.
- Water and sewer lines for a kitchen and bathroom, and a heat source such as a ductless heat pump.
When does converting a garage stop making sense?
It depends on the garage itself. A cracked or settling slab, low walls, rot at the sill or a garage that sits in a setback can make repair cost close to new construction. We inspect first and price both paths if the answer is unclear.
What does a garage conversion cost?
National guides put garage conversions at roughly $50,000 to $150,000 before permits and fees, as of October 2026. Portland projects vary with the condition of the garage and the utility work. See the Portland cost guide.
Related
Rules as of October 2026, from the City of Portland ADU zoning summary (Zoning Code Chapter 33.205) and ORS 197A.425. Cost range from Block Renovation and Angi garage conversion guides.
Check your garage
Send your address and a photo description of the garage. We tell you whether it is worth converting.
Serving Portland, Beaverton, Lake Oswego, Milwaukie and Gresham.