Tiny & modular homes in Portland, OR

Many compact prefab and modular homes fit Portland's ADU rules. The Hewing Haus homes featured on this page, from a Pacific Northwest builder already building in the Seattle area and expanding down the West Coast, range from 200 to 800 square feet, so most sit under Portland's typical 800-square-foot cap for a detached ADU. Starting prices are listed on each model. Ask through ModelTown to confirm delivery, foundation and site requirements for your property.

Yes, in two main ways.

• As an ADU: a tiny or modular home on a permanent foundation that meets Oregon building code can be a backyard ADU.
• On wheels: Portland allows one occupied tiny house on wheels or RV on a lot that already has a house. It must stay on its wheels, sit at least 5 feet from the house, and connect to water, sewer and a dedicated GFCI-protected electrical circuit. Electrical and plumbing permits may be needed, and it can't be used as a short-term rental.
• It isn't allowed on an empty lot with no house.

Confirm the details for your lot with a Portland city planner (the city offers free 15-minute appointments).

In most cases, yes.

• Modular homes on permanent foundations are appraised the same way as site-built homes
• Portland's urban growth boundary constrains how much new land can be developed, which structurally supports values inside the boundary and makes infill housing such as ADUs comparatively valuable
• A well-built backyard unit can generate rental income and add resale value at the same time

Tiny homes on wheels are a different case: they are titled as RVs and tend to depreciate more like vehicles than real estate.

Yes, though Oregon is stricter than most states about rural development.

Oregon's land use system draws urban growth boundaries and protects farm and forest land aggressively, so a rural parcel is not automatically buildable. Confirm dwelling approval before you buy land, not after.

• Clackamas, Columbia and Yamhill counties offer larger parcels and lower land costs than the city
• Septic feasibility, well or water access, and wildfire hazard designation are the usual practical constraints

Factory-built modular homes are state-certified and must meet Oregon building code, while the county controls placement, foundations and utility connections.

A complete ADU project in Portland typically runs between $180,000 and $380,000, covering design, permits, foundation, utilities and the structure.

The single largest swing factor is the system development charge. Staying at or under 800 sq ft on an owner-occupied property waives it and saves roughly $15,000 to $25,000, which is often enough to change which model makes sense.

• Permits: four to eight weeks for straightforward projects
• Tree, historic or land use review: four to six months
• Portland's mature tree canopy means tree preservation requirements and root protection zones can add cost and time, so check your lot early

A factory-built home shortens the on-site build window, which matters in a wet climate.

Yes, and Portland has been an ADU-friendly city for over a decade.

• One attached and one detached ADU on a single-family lot in many zones
• Detached ADUs capped at 800 sq ft, and no more than 75% of the primary dwelling's floor area
• 20 ft height limit in most residential zones
• Rear setbacks typically 5 ft
• No owner-occupancy requirement since 2020
• No additional off-street parking required anywhere in the city

The financially significant detail is the system development charge. Portland waives SDCs for ADUs up to 800 sq ft on owner-occupied properties, worth roughly $15,000 to $25,000. Units above 800 sq ft, or on properties that are not owner-occupied, may still owe them. Straightforward permits typically clear in four to eight weeks; tree, historic or land use review can push that to four to six months.