When homeowners discover standing water or damp mud in their crawl space during an Olympia winter, their immediate fear is a broken plumbing pipe or massive underground spring. In reality, over 85% of crawl space water intrusions are caused by a surprisingly simple flaw: roof runoff discharging directly next to the foundation.
Western Washington receives heavy, sustained rainfall. A typical 2,000-square-foot roof catches roughly 1,250 gallons of water for every 1 inch of rain. During a 3-inch winter storm, over 3,750 gallons of concentrated water pour through your gutter downspouts. If those downspouts terminate at the corners of your home with short 2-foot splash blocks, you are dumping thousands of gallons of water directly into your foundation backfill zone.
Foundation backfill soil—the dirt excavated and replaced around your concrete stem walls when the house was built—is far looser and more porous than undisturbed native ground. Water discharged near the house immediately sinks straight down through the backfill, creating immense hydrostatic pressure that forces water under the footing and into your crawl space.
Many homeowners make the mistake of burying cheap black corrugated flex-pipe from hardware stores. Corrugated pipe is paper-thin, easily crushed by lawnmowers, clogs with tree roots within three years, and traps stagnant water in its ribbed corrugations.
We install commercial-grade, smooth-interior rigid Schedule 40 or SDR-35 PVC conductor pipe. We trench downspouts at a continuous 1/8-inch per foot slope away from the home, install in-line cleanout ports, and discharge the roof runoff safely to daylight, dry wells, or storm pop-up emitters at least 15 to 25 feet away from your foundation.