Mold Removal in West Linn, OR: Wet Slopes Above the Willamette

The wet side of the Willamette

NOAA's 1991 to 2020 normals record 50.4 inches of precipitation a year at a volunteer station near West Linn, at an elevation of roughly 680 feet. Portland International Airport records 36.9 inches and Hillsboro Airport 35.9, and the station at Oregon City records 44.8. A hillside house here carries more water through its roof, gutters, and below-grade walls than the airport figures suggest.

What the city's own slope map shows

West Linn's Natural Hazards Mitigation Plan includes a map of potential landslides that combines state landslide data (DOGAMI, preliminary) with a city layer of steep slopes greater than 25 percent. The steep-slope bands run along the Willamette River bluffs, the Highway 43 corridor, and the side of the city facing Willamette Falls and Oregon City. The map's own note says the information is preliminary and not intended for decisions about specific properties.

Where a lot slopes toward a house, the useful questions are where downspouts discharge, whether footing drains are clear, and whether a retaining wall is holding water against the foundation. Slope stability itself calls for a geotechnical engineer. Our gutters and drainage and crawl space and subfloor pages describe the moisture side.

Owner-occupied houses from the 1980s and 1990s

The American Community Survey (2020 to 2024) counts 10,395 housing units in West Linn with a median build year of 1988. Some 2,431, or 23 percent, were built in the 1990s, and 1,781 in the 1970s. About 544 homes, 5 percent, date to 1939 or earlier. Seventy-six percent of homes are detached houses and only 17 percent of households rent, the lowest renter share of any city we serve, so work here is mostly a single homeowner and a single house.

Willamette Falls, on the city's southern edge, shaped West Linn's history. The locks opened in 1873 and a paper mill began operating there in 1889.

Where we serve in West Linn

The city recognizes ten neighborhood associations, and its site names Willamette, Robinwood, Sunset, Savanna Oaks, and Parker Crest among them. We also serve Bolton and the rest of the city, along with nearby Lake Oswego, Oregon City, and Tualatin.

How the work is planned for West Linn homes

Seventy-six percent of West Linn homes are detached and only 17 percent of households rent, so a job is usually one owner and one house on a slope. The inspection follows water from the roof to the ground: downspouts, grading, footing drains, then the crawl space or lower level.

West Linn areas we serve

• Willamette
• Robinwood
• Sunset
• Savanna Oaks
• Parker Crest
• Bolton

Services for West Linn homes and buildings

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