A second home on the lot you already own.
Detached ADUs, garage conversions, attached additions and basement units for Portland-area homeowners. We draw it, permit it and build it. Licensed and insured.
How much does an ADU cost in Portland?
As of October 2026, a national cost guide published in June 2026 puts a new detached ADU at about $150,000 to $400,000 all in. Basement and garage conversions usually cost less because the shell exists. Portland waives system development charges for ADUs kept off the short-term rental market. We price your lot in writing.
What kinds of ADU can I build in Portland?
As of October 2026, Portland's zoning code lets you create an ADU four ways: convert part of the house, add onto it, convert an existing accessory building, or build a new detached one. Many lots can take two.
Detached ADUA standalone cottage set behind the house, up to 20 feet tall outside the setbacks.
Garage conversionReuse a detached or attached garage. Oregon law bars cities from demanding new parking for an ADU.
Attached ADUAn addition joined to the house, with its own door, kitchen and bath.
Basement ADUIn a house at least five years old, Portland lifts the usual size cap for a basement unit.
How we handle ADU design and permits · Compare every ADU type
What are the steps to build an ADU?
- Lot checkYou send the address. We read the zone, lot area, street frontage and any overlay.
- Visit and designWe measure, inspect the panel and sewer route, then draw to your budget.
- PermitsWe file the permit set, handle checksheets and the SDC waiver paperwork.
- BuildConstruction, staged inspections and final approval.
Which cities do we work in?
Portland and four neighboring cities. Oregon sets a statewide floor for ADUs, but each city writes its own size, height and review rules.
Portland
Up to two ADUs on many house lots, and an SDC waiver for units kept off the short-term market.
Portland ADU notesBeaverton
A Washington County city where state ADU protections apply alongside local code.
ADUs in BeavertonLake Oswego
One ADU per house, capped at 800 sq ft of gross floor area.
ADUs in Lake OswegoMilwaukie
Dropped its owner-occupancy and parking rules for ADUs in 2020.
ADUs in MilwaukieGresham
Allows up to 900 sq ft, but bars short-term rental of ADUs.
ADUs in GreshamCheck what your lot allows
Send us your address and a line about your plans. We look up the zoning, lot size and overlays, then tell you which ADU types are realistic.
Serving Portland, Beaverton, Lake Oswego, Milwaukie and Gresham.