Accessory Dwelling Units (ADUs)

While their forms vary, ADUs share some common traits. They’re always secondary housing units on single family residentially zoned lots and are a unique category of housing. ADUs also have some other distinguishing characteristics:

• ADUs are accessory and adjacent to a primary housing unit.

• ADUs are significantly smaller than the average US house.

• ADUs tend to be one of two units owned by one owner on a single family residential lot.

• ADUs tend to be primarily developed asynchronously from the primary house by homeowner developers.

• A large range of municipal land use and zoning regulations differentiate ADU types and styles, and dramatically affect their allowed uses

• Many informal ADUs exist compared to permitted ADUs.

These characteristics make ADUs distinct from normal housing. The Portland area is relatively friendly to the best practices of ADU development.