What causes wet basements in the Pacific Northwest?

Heavy rainfall, poor drainage, high groundwater levels, and foundation cracks are the leading causes of wet basements in the PNW.

Do you offer free inspections?

Yes, we offer free on-site inspections for waterproofing and mold remediation.

How long does waterproofing last?

A professionally installed waterproofing system can last 20–50 years depending on the drainage configuration and maintenance.

Basement Waterproofing In Redmond, WA

Redmond homes frequently deal with groundwater due to clay soil, slope issues, and seasonal rain cycles. Our team provides comprehensive waterproofing and moisture solutions to protect your home and prevent foundation deterioration.

1. Geology and Soil Conditions

The Redmond area lies within the Puget Lowland and is underlain by glacial and inter‑glacial sediments. A geotechnical evaluation notes that a site in Redmond is “near the contacts between Vashon Glacial Till, Older Alluvium, and Younger Alluvium.” Redmond+2Ecology Apps+2
The Vashon glacial till in this region typically consists of dense, unsorted material: “relatively dense, silty‑fine to medium grained sand trace to with gravel (Vashon Glacial Till) which continued to the termination depths of the explorations.” Redmond+1
Native soils studies for western Washington explain that glacial till often includes a “hardpan” or nearly‑impermeable layer at depths of about 18‑36 inches (or deeper) which impedes drainage and may create perched groundwater zones. Docslib
Implication: Homes with basements in Redmond often sit adjacent to soils that drain slowly due to dense till or fine‑grained deposits. When water enters the ground (rainfall, runoff, irrigation), it may become trapped or move laterally rather than percolating freely downward. That elevates the risk of basement walls and slabs being exposed to hydrostatic pressure or moisture migration.

2. Rainfall and Seasonal Moisture Load

The climate in Redmond involves frequent rainy days and a substantial wet season.
A blog article on local soil behavior states: “When Redmond’s autumn rains hit dense clay, even brief gutter overflow forces water straight into crawlspaces … The culprit is … dense clay that stores every drop of rain …” Osprey Exterior
The city’s stormwater information indicates: “11 billion gallons of rain falls in Redmond annually.” Redmond
Implication: Prolonged or repeated rainfall events saturate the soils around basements. With slow‑draining soils (see above), this leads to longer periods of elevated moisture, higher groundwater or perched water tables, and increased lateral/hydrostatic pressure on basement structures.

3. Topography and Drainage Characteristics

Redmond’s terrain includes upland plateaus, slopes, and variable elevations. In geotech reports: “Groundwater was encountered at ~10 feet below grade in one boring; perched groundwater could be present at shallow depths below the site during the winter months.” Redmond+1
The site conditions report also mentions that “soil & groundwater conditions … Groundwater likely present at or several feet higher than the lake surface elevation.” Redmond
Surface and subsurface water flows in this terrain can channel toward lower areas including basements, especially when grading or lot drainage is not optimized.
Implication: Homes situated on slopes, near higher terrain, or on lots where grade directs water toward the foundation are at a higher risk. When you combine this with slow‑draining soils and high rainfall, the odds of water intruding into basements significantly increase.

4. Combined Effect: Why Basement Water Risk Is Elevated in Redmond

Bringing everything together:

Basements in Redmond often border soils consisting of dense glacial till, clay/silt layers or low‑permeability substrates, meaning natural drainage is limited.
The area has frequent rainfall and many wet days; soils become saturated, and groundwater may rise or form perched zones.
Topography and drainage pathways may direct surface water or subsurface flow toward the foundation walls or slab edges.
The result: elevated hydrostatic pressure on basement walls and floors, increased likelihood of water ingress (through cracks, joints, seams), structural stress from soil expansion/contraction, and higher moisture accumulation in basements.
In short: If a basement in Redmond is not properly waterproofed or if drainage/grade is inadequate, the local soil + rainfall + terrain conditions multiply the risk of basement leaks, dampness or flooding.