A wet basement is more than an inconvenience.
If your basement includes finished living space, any kind of moisture can ruin carpeting, drywall, and framing. A simple case of condensation can buckle hardwood flooring on the level above and spawn harmful mold.
What Causes a Wet Basement?
The water in the basement most often comes from rainfall and melting snow. Even a small storm can trigger a problem. In tougher cases, the problem is rising groundwater, which may even be fed by an underground spring. Once the water accumulates around your foundation, it works its way inside through cracks, joints, and porous material.
Why Does My Basement Get Wet? Common Causes and Solutions
Check the Landscape Grade
Cause
When homes are constructed, the areas around the foundation are often backfilled with loose soil. And this backfill can settle more than the surrounding undisturbed soil. Over time, the backfill compresses, creating a slope (grade) that angles downward toward the foundation. These low spots near the foundation can cause water to drain toward the house and pool against the foundation, where it seeks entrance through cracks.
Solution
Walk around the entire house with a critical eye, making sure the grade (dirt or lawn) slopes away from your foundation and basement walls. The ground should slope away from the foundation with a vertical drop of about 8 inches for the first 2 feet of horizontal distance from the foundation wall. Regrading the soil around a foundation remedies the problem in many situations. This can involve trucking in substantial amounts of soil to reverse the direction of the slope.
Check the Slope of Patios and Walkways
Cause
Patios and walkways made of concrete or brick pavers might also contribute to the wet basement problem if they improperly slope toward the house. Correctly constructed paved surfaces should slope away from the foundation by a pitch of at least 1/4 inch per horizontal foot of distance.
Large patios are sometimes built with a slight funnel shape, so rain water flows toward the center and into a drain there. The drain sometimes is connected to an underground perforated drain pipe that leads out to the lawn, possibly with a pop-up relief valve. But it is not uncommon for improper construction or soil settling to cause a patio to develop a slope toward the foundation.
Solution
This can be a difficult problem to correct. Solid concrete slabs, if they are small enough, can sometimes be mud-jacked to change their pitch to slope away from the foundation. Brick paver patios and walkways can be disassembled for the base to be regraded to the proper slope and then reassembled.
It also might be possible to create a small curb or dam along the edge of the patio or walkway where it adjoins the house. This combined with good sealing of the paved surface, can help to direct water laterally away from the house rather than allowing it to drain downward along the side of the foundation wall.
Where such solutions are not practical, you can minimize the problem by making sure that the roofline above the patio is equipped with good roof gutters and downspouts that direct water away from the patio and foundation.
Basement window flooding
Basement windows can flood due to improper drainage in window wells, poor foundation grading, and faulty window well sealing.
- Inadequate draining in window wells: Ill-designed or poorly maintained window wells can collect water during heavy rainfall or snowmelt.
- Flawed grading: Bad grading around your foundation can lead to rainwater and melting snow pooling in your window wells.
- Poor window well sealing: Inadequate seals between the frame and walls can allow water to enter during rainy conditions.
Signs pointing to window issues include puddles, rotting and warping wood frames, rusted metal window frames, drafts, air leaks, and condensation on the window.
Defective or missing gutters and downspouts
PROBLEM: Missing gutters and downspouts cause rainwater to be directed toward the foundation perimeter. A downspout without an extender or splashblock is worse than no downspout at all. It is depositing the huge volume of rainwater from the roof in a single concentrated location near the basement.
SOLUTION: Place a minimum of one downspout per 50 linear feet of roof eave. Extensions should discharge water at least 4 feet beyond the wall. Sloped concrete sidewalks around basements are very effective in directing rain runoff.
Runoff
Rainwater or melted snow that isn’t routed away from the house is the most common cause of basement and crawl space moisture. Runoff percolates through porous topsoil and then stops at the compact soil near the base of the foundation. Hydrostatic pressure forces the water through gaps or cracks in walls and footings. Water also moves through porous walls by capillary action.
Do You Have a Runoff Problem?
A damp crawl space or wet basement walls and floors just after a storm or as snow melts are telltale signs the problem is runoff.
Look for ways runoff can enter your basement or crawl space. Check that the ground outside slopes away from your house at least 1 inch vertically for every 1 foot of horizontal travel. Then make sure downspout runoff isn’t pooling or percolating into soil near the foundation during a storm, and that downspout seams aren’t leaking; installing downspouts seams-out makes this check easy.
Next, check that driveway curbs are channeling runoff to the street. Look for unsealed cracks on the driveway surface, which can allow water to collect below grade. Some houses on hilly sites have a swale: a shallow trench with gently sloping sides and a gravel bed covered by topsoil and grass. The swale catches runoff, channeling it past the house or off to other drain systems. Unfortunately, a swale can eventually clog with silt and so can the original underground footing drains buried at the base of your foundation.
Patching Cracks and Sealing Walls
If you’re dealing with a full basement, start by patching cracks in the foundation and sealing basement walls. Use a polyurethane masonry caulk like Sikaflex or UGL’s Masonry Crack Filler
For 1/4-inch or larger cracks, use hydraulic cement, which expands as it dries. Leading products on the market include Thoro Waterplug , Custom Building Product’s Custom Plug and UGL’s Fast Plug .
For both basements and crawl spaces, you need to address outside entry points next by patching cracks in the driveway using cold-mix asphalt patching compound. For a concrete sidewalk or driveway, use ordinary cement.
You must be logged in to post a comment.