Beaverton is the westside city people drive through on the way to Hillsboro. Many still lump it in with “Portland metro,” but the permit file tells a different story. It’s Washington County, City of Beaverton Planning and Building, and the Beaverton Electronic Permitting System (BEPS). The development code (Chapters 40 and 60) caps a new ADU at 800 sq ft or 50 percent of the primary dwelling’s gross floor area, whichever is less.
That 50 percent limit is tighter than Portland’s 75 percent. A 1,200 sq ft ranch caps the ADU at 600 sq ft, well short of 800.
Wolf has built ADUs and modular homes in the Beaverton area. Deliveries come down I-5 from Battle Ground, cross the Interstate Bridge, and finish on Highway 26, TV Highway, Hall, Murray, or Scholls Ferry. Cooper Mountain and the Tualatin River edge share a city hall with 1950s lots near downtown. The soil, slope, and access are very different, though.
How Beaverton regulates ADUs
Beaverton allows one ADU per detached house in any zoning district that allows a single detached house as the main use. That includes some commercial districts. The path is typically a Type 1 ministerial review, a staff-level check against set rules, plus a building permit. There’s no hearing. If the lot isn’t a straightforward R zone, check the current land-use tables in Chapter 20.
The size limit is 800 sq ft or 50 percent of primary gross floor area, whichever is less. That applies to an ADU created by an addition or inside the existing house, and detached modular cottages are held to the same numbers.
Third-party summaries often list a low height limit for detached units. The examiner actually applies the underlying zone’s accessory-structure standards, so we check height for your specific zone. Setbacks, the distance a building has to sit from the property lines, follow the accessory-structure or dwelling standards in that zone as well. Our Oregon ADU rules guide covers the state side. For the numbers on your parcel, send us the address.
The statewide rules still apply: ORS 197A.425, no owner-occupancy mandate, and no extra off-street parking mandate for long-term units under HB 2001. Beaverton still sets siting, the 50 percent test, and fees.
Unincorporated Washington County lots with a Beaverton mailing address don’t go through BEPS. That includes West Slope edges, some Aloha-adjacent blocks, and county islands. Those lots go through county building plus Clean Water Services, which is a different process.
Models that fit 800 sq ft or half the house
Wolf doesn’t sell manufactured homes built to the HUD code, the federal standard for manufactured homes. Our homes are modular dwellings under Oregon’s BCD prefabricated-structures program. They’re placed on a local foundation with a city installation permit. They leave Battle Ground with the Oregon insignia, and Beaverton still inspects the foundation, the set, and the utilities.
- Model K (~432 sq ft). A one-bedroom ADU for when the house is big enough that 50 percent isn’t the limit.
- Model E (~616 sq ft). Two-bedroom flexibility under 800, still subject to the 50 percent test on smaller main houses.
Model J, at about 828 sq ft as published, is over 800. A Model J that works in Portland won’t work here. If the main house is 1,400 sq ft, 50 percent is 700, and even Model E needs a careful measurement. We check every model against your house’s living area.
Permits: BEPS, Planning, Building, and a CWS letter
Beaverton’s permit sequence is specific:
- Check zoning with Beaverton Planning (lot size, setbacks, utility access).
- Prepare building plans that meet city building-code standards.
- Submit a land-use application if Planning requires one for the scope.
- Apply for the building permit through Building Services, with the site plan, structural plans, and code compliance.
- Pull electrical, plumbing, and mechanical permits as needed.
- Pay fees.
- Schedule inspections (foundation, framing, plumbing, electrical, as they apply).
- Get final approval and occupancy.
All of that now runs through BEPS. You create a profile, apply, look up the file, request inspections, and pay fees there. It’s a separate system from Portland’s DevHub, Hillsboro’s ProjectDox, and Tigard’s portal. Uploading to the wrong westside city means starting over.
Clean Water Services requires Environmental Review before Beaverton issues the permit. That means a prescreen, then a Service Provider Letter (or a “not required” form). The SPL goes in with the city application. Cooper Mountain drainage, Fanno Creek, and the Tualatin tributaries are the reason. Without the CWS step, the BEPS file won’t move.
For building questions, the city’s published building line has been 503-526-2403. Planning is a separate desk, and our permit team works with both.
System development charges
Beaverton charges system development charges, one-time fees on new ADUs. A city building-code handout described when sanitary sewer SDCs apply. They kick in if the ADU is over 1,000 sq ft or the shared water meter has to be larger than ¾-inch. It cited a 2022 rate that may no longer be current.
Wolf’s typical ADU models are under 1,000 sq ft, but meter size still has to be checked. That meter question surprises people who assumed a small cottage skipped sanitary SDCs. Parks, water, transportation, CWS sanitary and storm, the Washington County TDT, and construction excise tax can all apply. We pull the current schedule for your project.
Tigard has an ADU SDC-exemption covenant program, and Salem waived its ADU SDCs. Beaverton hasn’t published anything comparable. Budget for SDCs until the city’s worksheet says otherwise.
Where Beaverton lots run into trouble
- Flat lots with access versus sloped lots with tight setbacks. Cooper Mountain and some lots south of Scholls Ferry have grade problems. Murrayhill and older central Beaverton more often run into limits on how big a building can be.
- Simple sewer lines versus long trenches and service upgrades. A 1960s house with 100-amp service needs a utility plan for the new home before anyone picks fixtures.
- Wide delivery versus narrow streets with trees, fences, and lines. Model K and Model E ship on different trucks.
- The 50 percent test. Once the garage is left out, the house is usually smaller than the owner thinks. That’s how an 800 sq ft plan turns into a 550 sq ft permit.
Trees, stormwater, and HOA design rules in planned developments add review rounds that BEPS won’t skip. If you have an HOA, tell us early. The city can approve a unit that the CC&Rs still block.
How people use these homes
Beaverton ADUs house parents and adult children. They also work as long-term rentals and guest cottages. Some support downsizing plans, where the owner eventually moves into the backyard and family takes the main house. Access to jobs via MAX, 217, and 26 keeps rental demand strong. Short-term lodging has its own local rules, separate from the ADU permit.
A granny flat or mother-in-law unit with a kitchen and bath is an ADU to Beaverton, whatever you call it. It goes through Type 1 review with the same 50 percent test and the same CWS letter as any other.
For a nearby example, see the historical Model B rental in Tigard. Model B is now offered only inside City of Portland limits. On a Beaverton lot, the narrowest option is the 12-foot-wide Model K.
Factory build and westside set days
Once BEPS issues the permit, the home is built in Battle Ground while site work moves forward. Highway 217, 26, and TV Highway bring the module onto the westside. On Hall, Murray, and Scholls Ferry, parked cars and school traffic decide when the crane can work. A side yard that’s the only pad location may need a crane as well.
On set day, the day the home is placed on its foundation, we weather-seal it. Then we do the mechanical and plumbing tie-ins. A two-piece plan needs a second day on site to join the halves.
Building indoors keeps Valley rain off the framing for the months it would otherwise sit exposed. The lot still needs a dry enough window for the foundation, trenching, and set. Fanno Creek and Cooper Mountain drainage bring review comments of their own. A summer set in Murrayhill and a February dig on Cooper Mountain are priced differently.
Beaverton water, CWS sanitary and storm, and PGE (or the local franchise in some pockets) are three separate utility contacts. Warranty work is a short drive from the Battle Ground factory, and we treat Beaverton as a local market.
What goes into a Beaverton proposal
The starting home price stays the same from lot to lot. The total project cost depends on site work, water meter upgrades, Clean Water Services requirements, transportation charges, and city SDCs. Two Beaverton properties with the same model can still come out at different totals. See our financing page.
Neighborhoods vary too. Downtown Beaverton and the Canyon Road mix are different from Murrayhill. West Slope faces Portland and sometimes files in a different jurisdiction. Progress and Scholls-edge lots sit near Tualatin and Tigard. Cedar Hills and the MAX corridor have different parking and delivery conditions than a cul-de-sac off Murray. Each can pick up different items on the BEPS checklist.
Neighboring cities write their own rules. Hillsboro caps ADUs at 750 sq ft and uses ProjectDox. Tigard allows two ADUs and has a parks-and-transportation SDC exemption packet. Portland uses DevHub and a 75 percent / 800 limit.
What we look at for a Beaverton lot
Bring the address, a backyard sketch, and any survey. A BEPS login from a prior permit or an HOA architectural packet helps too. If all you have is an address and a rough guess at the house’s living area, that’s enough to start.
The free property evaluation is our first look at zoning, setbacks, and what’s generally allowed. For Beaverton, that covers:
- City of Beaverton versus Washington County.
- Living area of the main house, for the 800 / 50 percent test.
- Zone, including whether the lot is in a commercial district that still allows a detached house.
- The BEPS path: land use plus building, plus trades.
- Intended use: family, long-term rental, or short-term.
As the project moves forward, we work through the site details:
- CWS prescreen and SPL.
- Water, sewer, storm, and electrical: laterals, the ¾-inch meter question, and the panel.
- The truck path from 26, 217, or TV Highway to the curb.
After we walk the lot and measure the house, you’ll get a proposal with the model, site work, and fees on separate lines. Tell us how big the house actually is, because the ADU can only be half of that. We’ll match a model to the number. Send the address.
