AGrannio

Can You Build an ADU in Portland?

Yes — Portland is governed by Oregon's statewide ADU law, which limits what the city can restrict. A 700 sq ft detached ADU here runs about $176,500–$288,500.

Construction in Portland runs about 6% above the Oregon average, so budget toward the higher end of these ranges.

Detached ADU (700 sq ft)

$176,500–$288,500

Garage conversion (400 sq ft)

$55,000–$100,500

Statewide protection

Yes

What applies in Portland

Oregon's statewide standard (ORS 197.312 (SB 1051, 2017; HB 2001, 2019)) is the starting point, but parcel-level rules, fees and design review are set locally. Confirm those details with Portland before design.

Estimate your Portland ADU cost

Your property

ADU type

Estimated cost in Oregon

$176,500 – $288,500

≈ $252–$412/sq ft turnkey · midpoint $232,500

$158,000
Construction
$41,900
Design & permits
$32,600
Site work
Good news — building an ADU in Oregon is very likely allowed.
  • iSize set locally. This state leaves ADU size limits to your city — typical caps run 600–1,200 sq ft. Check your local code.
  • ✓No extra parking likely required. Cities cannot require additional off-street parking for an ADU under Oregon's statewide rules.
  • ✓No owner-occupancy requirement. You can rent out both the main home and the ADU — you do not have to live on the property.
  • ✓Lot has room. A 700 sq ft ADU uses about 12% of your 6,000 sq ft lot — comfortably within typical coverage limits.

Rule basis: ORS 197.312 (SB 1051, 2017; HB 2001, 2019)

If you rent it out

$1,150–$1,875

est. rent/mo

7.9%

gross yield

13.7 yrs

payback

~$17,019/yr after a 7% vacancy allowance, before financing & maintenance.

Financed over 20 yrs at 7.5%, the build is about $1,873/mo — vs ~$1,525/mo in estimated rent.

Get your detailed feasibility report →

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.

Get matched with a vetted ADU builder in Portland

Tell us about your project and we'll introduce you to a builder who works in your area. Free, no obligation.

Other Oregon cities

SalemEugeneGreshamHillsboroBendBeavertonMedford

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.