Mold Removal in Hillsboro, OR: Newer Homes and the Tualatin Valley

Most of the city is younger than 1990

The American Community Survey (2020 to 2024) counts 43,576 housing units in Hillsboro with a median build year of 1997. Some 28,894, or 66 percent, were built in 1990 or later, including 19,070 in 2000 or later. The census counted 27,664 residents in 1980 and 106,447 in 2020. Only 24 percent of homes predate 1980. Half of households rent, and a third of homes are in buildings with five or more units.

Newer areas include Orenco, Tanasbourne, and South Hillsboro. Reedville is a neighboring unincorporated community that we also serve.

Newer houses and Oregon's ten-year limit

Moisture problems in a young house often trace to something that was built wrong rather than to age: a missing flashing, a plumbing connection, a bath fan ducted into an attic. Oregon's statute on construction claims (ORS 12.135) generally requires a claim over residential construction to be filed within ten years after substantial completion, which it defines as the earliest of written acceptance of the work, a certificate of occupancy, or the owner occupying the home. A house finished in the last ten years may still be inside that window.

Whether a particular claim qualifies is a question for a construction-defect attorney. What helps in either case is a record made early: dated photographs, moisture readings, and a written scope showing where the water is coming from. See our mold inspection and testing page.

Drier than the rest of the metro, and colder at night

NOAA's 1991 to 2020 normals record 35.9 inches of precipitation a year at Hillsboro Airport, the lowest annual total among the NOAA normals stations in the Portland area, against 36.9 at Portland International Airport and 44.8 in Oregon City. The same airport station records about 64 days a year with lows below freezing, about twice as many as the Portland airport (about 32).

Less rain does not remove the moisture risk in a tight house, because showers, cooking, and laundry load the air regardless of weather. The EPA recommends keeping indoor humidity below 60 percent, ideally 30 to 50 percent. Below-freezing nights matter most for pipes in unheated garages and crawl spaces. See water damage and moisture control.

The Tualatin River in February 1996

The Tualatin River forms part of Hillsboro's southern boundary. In the storm of February 6 to 9, 1996, Hillsboro recorded 6.70 inches of rain in four days, above its previous four-day record of 5.91 inches from 1974, according to the Oregon Climate Service. The Tualatin River at Farmington crested at 37.2 feet, above the 37.0-foot record from 1933 and well over the 32-foot flood stage. A hydrologist with the Oregon Department of Forestry rated the river's floods at two gauges as equivalent to events of 75 years or more in a preliminary review.

That flood followed a January snow and ice episode and a deep freeze, which is the kind of sequence that leaves ground saturated. For homes near the river, the practical step is to check the FEMA flood map for the address and to keep a record of any water that enters a crawl space or basement.

How the work is planned for Hillsboro homes

Two-thirds of Hillsboro homes were built in 1990 or later, so inspections start with how the house sheds and vents water: flashing, window seals, bath fan ducts, the attic, and the crawl space. Findings are written up with dated photographs and readings, since a newer house may still be inside Oregon's ten-year window.

Hillsboro and nearby areas we serve

• Orenco
• Tanasbourne
• South Hillsboro
• Downtown Hillsboro
• Shute Park
• Reedville (unincorporated)

Services for Hillsboro homes and buildings

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