St. Helens is the Columbia County seat, a river town on Highway 30 with the Columbia on one side and fir country on the other. City of St. Helens and unincorporated Columbia County are different reviewers, so a Strand-area address and a five-acre parcel off Pittsburg Road can share a mailing city and still file in different systems. Columbia City, a mile upriver, has its own city hall too.
Wolf builds in Battle Ground, in Clark County across the Columbia. There’s no bridge at St. Helens, so delivery crosses the Columbia into Portland and then runs northwest on Highway 30 along the river. We don’t have a recorded Wolf delivery in St. Helens yet, but the city is inside our Washington-and-Oregon turn-key area, and we review lots here the same way we do in Scappoose and the rest of the county.
City of St. Helens or Columbia County first
Look up the parcel before you sketch anything. If the lot is inside city limits, St. Helens Community Development and the St. Helens Municipal Code apply. If it isn’t, you’re in county land use, even when the mail says St. Helens.
Oregon cities over 2,500 must allow at least one ADU on qualifying single-family lots inside a UGB (ORS 197A.425), and HB 2001 blocked owner-occupancy and extra off-street parking mandates for long-term units. Local rules still matter. Read the Oregon ADU rules guide and the Columbia County ADU rules guide. The city or county reviews the site plan and issues the permits. We coordinate that process for your project.
Inside St. Helens, the city has used “auxiliary dwelling” language for years (SHMC Chapter 17.128 in the code outline), and the size numbers have changed over time. The 2003 chapter (Ordinance 2875) capped the unit at 30 percent of living area or 1,000 square feet, whichever is less, with a 220-square-foot minimum. A 2022 city packet described a larger limit: 75 percent of living area or 1,200 square feet, whichever is less. Middle-housing changes after HB 2001 also made a second detached dwelling an outright use in some zones, which is a separate path from an auxiliary dwelling. Because these numbers keep changing, confirm the current SHMC and handout the week you file. Anything not covered there depends on the lot. Ask with the address.
The county’s ADU packet includes a chart with different size and owner-occupancy notes for Columbia City, Clatskanie, Rainier, Scappoose, Saint Helens, and Vernonia. A St. Helens city lot can’t be priced from the Scappoose row, and a Rainier lot can’t be priced from St. Helens rules.
Unincorporated Columbia County has its own rural residential path under Ordinance 2023-1. The parcel generally needs at least two acres, the ADU is limited to 900 square feet of usable floor area, there’s one ADU per lot or parcel, and the unit must sit no farther than 100 feet from the primary dwelling. Water, wastewater, road access, and service by a fire protection district are all screening items. The ADU may not be used for vacation occupancy, and a rural ADU approval can’t be used to justify a partition. Don’t apply the city’s 1,200-square-foot figure to a rural lot, or the county’s two-acre rule to a city lot.
How St. Helens takes a permit
We file a complete packet, because missing site plans, utility letters, or a truck path send it back. Here’s the order we work in:
- Confirm a dwelling is allowed in the zone, using city maps and the current SHMC (auxiliary dwelling or second detached dwelling, depending on what the lot supports).
- Plot plan: existing house, proposed cottage, the zone’s setbacks, parking, utilities, and a truck path that works on a downtown street or a Highway 30 driveway.
- 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. St. Helens still reviews the foundation, placement, utilities, and any appearance or siting standard in the current code.
- Submit to the city (or Columbia County Land Development Services if unincorporated), including how water and wastewater will be handled. Site prep is part of the job.
- Inspections as called, then occupancy. Keep the approved drawings on site.
A city submittal usually includes the application, a site plan with property lines and setbacks, floor plans, water and wastewater details, and any extra sheets the current auxiliary-dwelling chapter requires. Oregon BCD inspects the module in the factory, and St. Helens inspects the foundation, placement, and utility connections.
County rural files need the two-acre, 100-foot, 900-square-foot, septic, and fire-district checks before a floor plan is useful. The county asks applicants to talk with the Planner On Duty and to submit a detailed site plan showing distances to property lines, septic, parking, entrances, and driveway length. Ordinance 2023-1 and the zone’s own chapter are the starting point, and a parcel can pass the two-acre and 100-foot tests and still fail on septic, access, or a resource-zone setback.
Lots we see
Downtown St. Helens has a real river main street, which is why people want a backyard unit within walking distance of it, and also why a crane on a fully parked block takes planning. The older grid off the Strand and Columbia Boulevard can be tight, with short lots, on-street parking, older houses, and mature trees. Upland and newer westside plats off Highway 30 are wider and often HOA (homeowners association)-controlled, with drainage and overhead-line questions, and they’re still subject to the current SHMC size limit. Toward Columbia City the two cities run together on the ground but stay separate on paper. West of town, McNulty and Pittsburg-area parcels look rural from the road; some are city and some are county. Check GIS first.
River-adjacent and low parcels raise floodplain and geotech questions. If the lot is in a flood overlay, mention it on the evaluation.
Delivery on Highway 30
Delivery from Battle Ground takes about half a day when the last mile is clear. Highway 30 is the usual route from I-5 and I-205. A 12-foot-wide Model K is easier to get in than a 616-square-foot E on a street with parking on both sides, and overhead lines, firs, and a driveway built for a passenger car still decide the day. Drawbridge traffic, mill-shift hours, downtown on-street parking, and narrow approaches off the river road all affect when a module can roll, so we put them on the schedule early.
Models under a changing city cap
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). One-bedroom ADU on a typical city lot.
- Model E / Model F (~616 sq ft). Two bedrooms when the current city size rule allows it.
If the house is small, a percentage-of-living-area test can limit you before the square-foot cap does, so measure first. Model J (~828 sq ft) and Model L need a check against the current SHMC. They were over the 2003 1,000-square-foot cap and under the 1,200 cap, so the code in effect when you apply is what counts. County rural lots use the county’s 900 square feet of usable floor area instead.
ADU, tiny home, or granny flat
If it has a kitchen and bath, the city treats it as a dwelling. “Tiny home,” “granny flat,” and “ADU” go through the same jurisdiction check and carry the same factory insignia. Family use and long-term rental are the usual choices. Short-term rentals have separate local rules, and Columbia County prohibits vacation occupancy of the ADU on county lots. 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, parking work, and any required siding or siting match after reviewing the property. Factory construction keeps the home out of river-town rain, but city or county review and site prep still drive 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. St. Helens doesn’t offer the same ADU SDC waiver as Salem, so Oregon SDCs and local connection fees go into the proposal after we confirm current fees for your property.
A Strand backyard and a Pittsburg Road acre won’t cost the same, so we quote after a property evaluation. Financing is usually a HELOC, cash-out refinance, or a construction-to-permanent lender who has worked with factory-built ADUs. See financing.
Turn-key service and nearby cities
St. Helens is turn-key Oregon for us: permitting support, site work, production, delivery, and setup as one job. Punch-list work goes to the crew that set the home, and they come from Battle Ground through Portland and up Highway 30. None of that changes the SHMC.
Scappoose, the next city south on Highway 30, has its own development code. Columbia City, Rainier, Clatskanie, and Vernonia are other Columbia County cities with their own rows in the county packet. Portland is in a different county with different SDC rules.
Weather, soils, and utilities
The lower Columbia is wet from fall through spring, and the house is built indoors. On the lot, silts, winter water, and high water tables near the river affect excavation and erosion control. Summer is the easier set window. Winter sets happen too, with tighter site controls.
Most in-city lots are on city water and sewer. You still need to check laterals, a cleanout, and whether the electrical service can carry a second dwelling. Outside city limits you’re often on well and septic, where the rural ADU rules and septic design usually decide the project. If you don’t know which you have, it’s the first thing we check.
Site work
Foundation excavation, trenching, grading, and minor tree work are part of a normal St. Helens job. A downtown alley that looks like a delivery path, or a Highway 30 driveway built for a passenger car, is why we measure access early. We bring a standard delivery trailer, and a crane when the swing needs it. We weather-seal the same day when we can, then finish the mechanical and plumbing tie-ins. Two-piece plans add a day to join the halves.
What to send
An address is enough to start. Useful extras: a survey, a tax-lot and zoning printout, a prior planning letter, the square footage of the existing house (needed if a percentage-of-living-area test still applies), photos of the backyard and the street approach, and whether the unit is for family, long-term rental, or a cottage you might live in. We check city versus county, the size rule, utilities, and whether a truck can reach the pad.
If you’ve already picked a model, we’ll still check it against the current city chapter or the county’s 900-square-foot usable-area cap before treating it as the plan. If a lot won’t clear the size rule or can’t take a truck, you’ll hear that at the evaluation.
After the set
Inspections, walk-through, punch list, keys, and warranty. St. Helens inspectors sign off on occupancy for city lots, so keep the approved drawings on site until they do.
Send the address. Tell us city or county, where the building would sit, and whether it’s for family, rental, or you. We’ll match a model to the size cap that applies.
