ADU Craft Portland

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ADU types we build in Portland

Four ways to add a legal second home, handled by one team from drawings to final inspection.

Small backyard home (ADU): A wooden deck with glass railings attached to a house in a forest Detached ADUNew construction in the yard. The most separation from the main house, and usually the largest budget. Detached garage Garage conversion ADUTurns an existing garage into living space. The slab and walls decide whether it pencils out. Small backyard home (ADU): A small wooden building with a green door Attached ADUAn addition sharing a wall with the house, with a separate entrance. Finished attic room: An empty attic room with light grey wood flooring and a modern sputnik chandelier Basement ADUFinishes the space under the house. Ceiling height, egress and moisture are the key checks.

ADU design and permits

Site plans, structural and energy work, the permit set, checksheet responses and the SDC waiver application.

How design and permits work

Which ADU type suits my property?

Look first at what is already standing. Many older Portland houses have a full basement with its own stair, which can be the most direct route to a second unit. A sound detached garage is the next candidate. An open, reasonably flat backyard points to a new cottage, and a house with room at the side or rear may suit an addition.

Then think about who will live there. A long-term tenant usually wants a private entry and some distance from the main house. An aging parent may value a ground-floor unit with no steps. Those goals can matter more than the price difference between types.

Can I combine two ADU types on one lot?

Often. As of October 2026, Portland allows two ADUs with a house in the R20 to R2.5 zones when the lot meets the minimum size, fronts a City-maintained street and sits outside the "z" overlay. Only one of the two may be attached to the house. A basement unit plus a backyard cottage is a common pairing. See our two-ADU guide.

How do the limits compare?

  • Detached ADU: 20 feet tall outside required setbacks, 15 feet inside them; at least 40 feet from the front lot line or behind the rear wall of the house.
  • Garage conversion: converting an existing accessory structure is one of the four paths the code allows; the usual size limit still applies.
  • Attached ADU: 75% of the house's living area or 800 sq ft, whichever is smaller.
  • Basement ADU: exempt from that size limit when the house is at least five years old.

Portland limits as of October 2026, from the City of Portland ADU zoning summary (Zoning Code Chapter 33.205). Suburban cities set different numbers; see areas.

Check 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.