ADUs in Oregon: What Contractors and Homeowners Should Expect in 2025

Accessory dwelling units — ADUs — continue to punch above their weight in Oregon's residential permit data. In both Salem and Portland, ADUs remain among the fastest-moving residential permits, and contractors with a repeatable model are booking well into the next construction season.

Why ADUs keep permitting well

Oregon's statewide land-use rules require most cities to allow ADUs on single-family lots, and both Salem and Portland have streamlined review pathways for standard configurations. Detached new-builds between 600 and 900 square feet dominate the current pipeline, with garage conversions holding a steady second place.

Cost expectations

Detached ADU costs in the Willamette Valley currently range from roughly $220 to $340 per square foot for turnkey builds, depending on finish level, site access, and utility runs. Garage conversions can pencil lower when existing framing and foundations are usable.

What contractors are doing differently

• Offering fixed-price packages built around 2–3 pre-designed plans.
• Pre-negotiating utility upgrades with local jurisdictions.
• Bundling ADU builds with primary-home remodel work to smooth crew scheduling.

For related context, see our Salem residential building boom report.