Why Is My Crawl Space Wet Every Winter?

By mid-winter, weeks of rain leave the soil around Olympia homes saturated. Water that cannot soak in moves sideways along the easiest path, and the gravel and loose soil around a foundation is often that path. It seeps through foundation vents, gaps and the soil under the vapor barrier, and pools on the low side of the crawl space.

The biggest single cause is often roof water. A roof sheds hundreds of gallons in a heavy storm. If gutters overflow or downspouts empty next to the house, that water goes straight into the soil beside the crawl space. Clean gutters, add capacity where they overflow and extend downspouts well away from the foundation.

Soil around houses settles over time, and the slope that once carried water away can reverse. On hillside lots, especially on the Westside, water from uphill flows toward the house. Regrading the soil or adding a drain on the uphill side can redirect it.

Not all crawl space water is rain. A drip from a supply line, a cracked drain or a leaking toilet seal can wet one area under the house all year. If water appears under one room even in dry weather, suspect plumbing.

Standing water raises humidity under the floor, soaks insulation, invites pests and lets mold grow on joists. Over time, wet wood can rot. Moisture also rises into the house, causing musty smells and cupping floors.

Pumps standing water out, removes wet insulation, dries the framing with dehumidifiers and finds the cause. See crawl space water damage for details.

Options include a perimeter drain with a sump pump, a heavier sealed vapor barrier, better gutters and grading, and in some homes a crawl space dehumidifier. A drainage or foundation contractor can recommend the right mix.

Traditional crawl spaces have vents to let air through. In a damp climate, outside air is often wet, so some homes do better sealed with a dehumidifier. Ask a contractor which suits your home.

Groundwater and seepage are usually excluded from homeowner policies. A burst pipe under the house is often covered. Fixing drainage is cheaper than repeating cleanup each winter.

Look in the crawl space after the first big storm in fall and again in late winter when the ground is wettest. Take a photo each time to compare.

You may notice the effects of a wet crawl space before you look below: a musty smell that gets stronger in winter, wood floors that cup, windows that fog more than usual, and more spiders, beetles or mice. Each is a reason to open the access and look.

A healthy crawl space has an intact vapor barrier lying flat, insulation snug against the subfloor, no standing water, dry wood and no musty smell. Ducts are connected and wrapped. If yours looks like that in late winter, it is in good shape.

For drainage or encapsulation work, get more than one opinion, ask what the work will fix and what it will not, and look the contractor up with the Washington L&I contractor lookup.

Before spending on drainage, try the simple fixes: clean and enlarge gutters, extend every downspout, regrade low spots next to the walls and fix any plumbing drips. Many crawl spaces stay much drier after these steps alone.

If water still collects, a perimeter drain and sump, a sealed vapor barrier or a crawl space dehumidifier may be needed. These cost more but end the yearly cleanup.

If the furnace or ducts are in the crawl space, standing water there can damage them and send damp air through the house. Have a heating contractor check them after any flooding.

Start with roof water, then grading, then drainage. Most Olympia crawl spaces can be kept dry with the right mix.

The best time to look is a day after a big storm, when water has had time to reach the crawl space. Bring a flashlight and your phone for photos.

Renters who notice musty smells or damp floors should tell the landlord early.

Water under the house? Call (360) 325-8833.

Winter water under the house is common here but fixable. Start with gutters and downspouts, then look at grading and drainage.

Questions about why is my crawl space wet every winter? Call (360) 325-8833 to reach a local Olympia provider, 24 hours a day.