Lake Oswego sits on the Willamette and around Oswego Lake, close enough to Portland that people assume Portland’s 75 percent rule applies. It doesn’t. Projects here go through the City of Lake Oswego under Community Development Code LOC 50.03. Most of the city is in Clackamas County, but city limits also touch Multnomah and Washington counties. A First Addition address and a Stafford-area parcel can share a mailing city and file in different systems.
Wolf builds in Battle Ground, across the Columbia in Clark County. Delivery runs I-5 / I-205, then 217, Highway 43, or Kruse Way. We haven’t delivered a Wolf home in Lake Oswego yet. The city is inside our turn-key Washington and Oregon service area, so we review lots here the same way we do in Tigard, Portland, and West Linn.
City of Lake Oswego or unincorporated county
Pull the parcel before you sketch a backyard. Clackamas CMAP is the public map for Clackamas lots. If the lot is inside city limits, Lake Oswego Planning and Building handle the packet. If it isn’t, you file with the county, even when your mailing address says Lake Oswego. West Linn has its own city hall, and Tigard is in Washington County.
Oregon cities over 2,500 people must allow at least one ADU on qualifying single-family lots inside a UGB (ORS 197A.425). HB 2001 blocked owner-occupancy and extra off-street parking requirements for long-term units. For county requirements, read our Clackamas County ADU guide. See the Oregon ADU rules guide for the statewide ADU rules and LOC 50.03 for the city rules.
Inside Lake Oswego, the ADU standards we use on evaluations are in LOC 50.03 (the city’s published ADU page and the 50.03.004 accessory-use standards; confirm the current section when you file):
- An ADU can be a conversion of existing floor area, an addition, or an accessory structure on a lot that already has a single-family dwelling.
- Public services must serve both dwelling units.
- Size: maximum 800 square feet of gross floor area, except where part of a dwelling existing as of August 2, 2018 is converted to an ADU. In that case, up to 200 square feet of circulation (halls, stairs), chimneys, and heating and ventilation systems can be excluded from the calculation. That exception covers conversions of pre-2018 space, not a new modular cottage.
- No more than one additional unit.
- The unit has to meet the site development requirements of the underlying zone, or sit in a lawful nonconforming structure or one previously granted a variance. A minor variance is available from ADU design standards, zone dimensional standards, or the Oswego Lake setback in order to site an ADU.
- ADUs are not allowed in the R-W (Residential-Waterfront) zone. They’re allowed in the city’s other residential zones. In R-5, R-3, R-2, and R-0, the ADU has to go with a detached single-family home.
Trees, the lake setback, and design overlays (Evergreen and others) mean even a simple 800-square-foot cottage needs a careful site plan. Accessory-structure height in many R zones is the lesser of 24 feet or the height of the primary house, so confirm it for your zone. If a number isn’t in the current LOC 50.03 or the city handout, it depends on your lot. Ask with the address.
Unincorporated lots with a Lake Oswego mailing address go through Clackamas County planning and building instead, under ZDO 839 for ADUs, with a different size table. Parts of the city in Multnomah or Washington County need a map check before anyone applies LOC 50.03.
How Lake Oswego takes a permit
Lake Oswego Planning expects a complete file. If the tree plan, lake-setback sheets, or truck route are missing, the file sits until they’re resolved. Here’s the sequence we use:
- Confirm the zone allows an ADU. R-W is out, the other residential zones are the starting point, and public services have to serve both units.
- Draw the plot plan: existing house, proposed cottage, the zone’s setbacks, the lake setback if it applies, tree locations, utilities, and a truck or crane route that works with First Addition street parking or a Palisades driveway.
- Prepare the engineered modular plan set. Wolf homes are modular, built in Battle Ground under Oregon’s BCD prefabricated-structures program, delivered with a state insignia of compliance, and placed on a local foundation. They aren’t HUD (the federal standard for manufactured homes) manufactured homes, and they aren’t on wheels. Lake Oswego still handles the foundation, placement, utilities, trees, and design.
- Submit to the city (or the county if unincorporated), including how water and wastewater will be handled. Site prep (grading, foundation, sometimes tree work) is part of the scope.
- Schedule inspections as called, then get occupancy. Keep approved drawings on site until the inspector signs off.
A typical city submittal includes the application, a plot plan with existing and proposed structures, the engineered modular set, foundation and connection drawings, utility letters, and tree and overlay sheets when they apply.
Lots we see
First Addition still feels like a streetcar-era grid, with short blocks, older houses, on-street parking, and mature street trees that often shape the whole project. Lake Grove has wider lots near the commercial area and a different approach off 217, but HOA (homeowners association), tree, and drainage questions still come up. Palisades and Mountain Park add grade, retaining, HOA packets, and driveways built for a passenger car. Lake-adjacent lots that aren’t zoned R-W still carry the Oswego Lake setback, and R-W lots can’t have an ADU under the published use table. A water view doesn’t make a lot an ADU site until the zone and setback check out.
Delivery from Battle Ground is a metro run. We still measure overhead lines, turnaround room, and whether the home is a single-wide K or a wider E, because a 14-foot module on a First Addition block needs more room than a narrow single-wide.
Models that fit 800 gross square feet
Wolf doesn’t sell HUD-code manufactured homes, and a home on wheels doesn’t count as an ADU here.
- Model K (~432 sq ft). A one-bedroom ADU well under the cap on a typical residential lot.
- Model E / Model F (~616 sq ft). Two bedrooms, when the 800-square-foot limit, coverage, and the zone all allow it.
Model J (~828 sq ft) is over 800 gross square feet. The 200-square-foot circulation exclusion applies only to converting pre-August 2, 2018 space inside the house, so it can’t stretch the limit for a new detached cottage. If you’ve already picked a model, we still check it against 800 gross square feet before treating it as the plan.
ADU, tiny home, or granny flat
If it has a kitchen and bath, Lake Oswego treats it as a dwelling. “Tiny home,” “granny flat,” and “ADU” all describe the same building, with the same 800-square-foot limit, the same tree review, and the same factory insignia. Family occupancy and long-term rental are the usual uses. The city regulates short-term rental lodging separately in its use table, so don’t assume an ADU permit allows a vacation rental. Tell us the intended use on the evaluation.
Cost and timeline
The model gives us a reliable starting home price. We price trenching, electrical capacity, tree work, lake-setback siting, and any design requirements after reviewing the property. Factory construction protects the home from Valley rain, but city review and site preparation still affect the schedule.
The Model K starts at $85,500 for the home itself. Permitting, delivery, installation, and site work are listed separately in your property-specific proposal. Lake Oswego doesn’t offer the ADU SDC waiver that Salem or Portland do, so we confirm current fees and local connection charges for your property before we write the proposal.
A First Addition backyard and a Palisades acre won’t cost the same, mostly because of tree removal and any lake-setback variance. We quote after a property evaluation. Financing is usually a HELOC, a cash-out refinance, or a construction-to-perm lender who has worked with factory-built ADUs. See financing.
Climate, soils, and utilities
The Willamette Valley is wet from fall through spring, which is why the house is built indoors. On site, silts, winter groundwater, and lake-adjacent soils affect excavation and erosion control. Summer is the easier set window, and winter sets take tighter site management.
Most in-city lots are on city water and sewer, and LOC 50.03 requires public services for both dwellings. That still leaves lateral length, the cleanout location, and whether the electrical service can handle a second dwelling. Outside city limits you may be on different providers. If you don’t know which utilities serve your lot, that’s the first thing we check.
Delivery and site work
I-205 and 217 are the usual routes from Battle Ground. Highway 43, Kruse Way, and Boones Ferry each make a different final approach, and school traffic, on-street parking in First Addition, and a narrow approach off the lake road all come up on evaluations.
Foundation excavation, trenching, grading, and tree work are part of a normal Lake Oswego job. A First Addition curb that looks like a delivery path, or a Palisades driveway built for a car, is why we measure access early. On set day we use a standard delivery trailer, plus a crane when the swing requires one. We weather-seal the same day when we can, then complete the mechanical and plumbing tie-ins. Dual-wide plans add a day to join the two halves. Tree protection fencing goes on the schedule well before delivery.
This is turn-key Oregon work: permitting support, site work, production, delivery, and setup as one job, with punch-list visits a short metro drive away. Tigard has its own 800-square-foot detached cap under a different code, Portland has different SDCs, and West Linn and Oregon City are Clackamas neighbors with their own code chapters.
After the set
Next come inspections, a walk-through, the punch list, keys, and the warranty. Lake Oswego inspectors still handle occupancy on city lots.
What to send
An address is enough to start. It helps to include a survey, a tax-lot and zoning printout, a tree inventory or prior tree permit, any prior planning letter, the square footage of the existing house, photos of the backyard and street approach, and whether the use is family, long-term rental, or a cottage you might live in. We’ll check city versus county, R-W versus other zones, the 800-square-foot cap, trees, the lake setback, utilities, and whether a truck can reach the pad. If the lot is zoned R-W or the pad can’t fit a home under 800 square feet, you’ll hear that before you pick a floor plan.
Send the address. Tell us city or county, the zone if you know it, and where the building would sit, and we’ll match a model to the 800-square-foot cap.
