Residential drafting in Oregon
We draft permit sets across the Portland metro, in Multnomah, Washington, and Clackamas counties.
Oregon sets a floor that every city has to meet, but the size limits, setbacks, and review steps are local and they differ more than people expect. We draw to the jurisdiction you are filing in.
What each Oregon city allows for ADUs
Size, setback, and unit rules for an accessory dwelling unit, city by city. Each city page carries the code section behind every number.
| City | Maximum size | Side and rear setback | How many units | Rented separately |
|---|---|---|---|---|
| Beaverton | 800 sq ft | Base zone, 5 ft rear if short | One | Yes |
| Happy Valley | 50% of the house, capped at 1,000 sq ft detached | Base zone standard | One | Yes |
| Hillsboro | 250 to 750 sq ft | Base zone, 3 ft if very small | One | Yes |
| Lake Oswego | 800 sq ft | Base zone standard | One | Yes |
| Oregon City | 800 sq ft or 60%, whichever is less | Base zone standard | One | Yes |
| Portland | 800 sq ft or 75%, whichever is less | 5 to 10 ft by zone | One, or two on a qualifying lot | Yes |
| Tigard | 800 sq ft detached | Base zone, 5 ft rear if short | One detached | Yes |
| West Linn | 1,000 sq ft attached; 1,000 or 75% detached | Base zone standard | One | Yes |
Outside this list? Send the address. We take work in the surrounding counties case by case.
What the code allows for ADUs
Does Oregon law let me build an accessory dwelling unit?
Yes. State law requires cities over 2,500 people to allow at least one accessory dwelling unit for each detached single family house inside the urban growth boundary (ORS 197A.425). Cities cannot require the owner to live on site or demand additional off street parking for the unit.
Then why do the rules look different in every city?
Because the state sets a minimum, not a standard. Size caps run from 750 square feet in Hillsboro to 1,000 in West Linn, and Portland exempts a basement conversion from the limit entirely. Oregon City caps the unit at 60 percent of the house, Happy Valley at 50 percent, and Hillsboro, Beaverton, and Lake Oswego use no percentage test at all. Setbacks, height, and placement are all local. The comparison above shows where they diverge.
Do I need a land use approval before the building permit?
In several of these cities, yes. Oregon City requires a Type I minor site plan and design review run alongside the building permit. Beaverton requires a Type 1 accessory dwelling unit application through Planning. Hillsboro requires Zoning Review approval before the permit can issue, though the two can run concurrently. Portland, West Linn, Tigard, and Happy Valley handle a code compliant unit through the building permit alone.
Are there fee waivers?
Sometimes, and they come with conditions. Portland waives all city system development charges in exchange for a recorded covenant barring short term rental anywhere on the property for ten years. Lake Oswego does the same, using a ten year covenant against rentals under 31 days. Tigard exempts city transportation and parks charges for a unit of 1,000 square feet or less under a similar covenant, and that exemption sunsets July 31, 2027. Beaverton has no waiver and charges accessory units directly. None of these waivers cover county or utility charges.
Can I use it as a short term rental?
It depends on the city and it is usually the most restricted use. West Linn and Happy Valley both require the owner to live on the property. Oregon City treats a stay under 30 days as a bed and breakfast use requiring a conditional use approval with a public hearing.
Sources: ORS 197A.425. ORS 93.277. HB 2138, operative January 2027. Last checked August 2026.
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