What's a Wet Basement and How Do You Deal With It?

You can try some simple fixes yourself

A moldy storage room in basement of house
••• Erik Dreyer/The Image Bank/Getty Images

Most basements present at least the possibility that wetness will get inside, simply by virtue of the fact that they're built into the ground. Water in the soil can put constant pressure on basement walls, and water follows the path of least resistance. The next think you know, you have a wet basement.

Water can find its way into a basement over time and some obvious signs, from efflorescence to spalling, can point to a problem.

Be Safe, Not Sorry

Check for signs of dampness if you're buying a house with a basement. It's better to find out before you buy than after, and you can't always rely on seller disclosures. Sellers might not know about the condition, or they could intentionally fail to disclose the water problems for any number of reasons.

It can be expensive to dry out a basement. Always get an independent home inspection by a qualified and accredited professional, but it never hurts for you to personally take a look around as well.

Signs of a Damp or Wet Basement

Know what to look for if you decide to inspect the basement yourself. Keep an eye out for water stains along the walls or floor. This could be caused by something as simple as an overflowing laundry tub, or it could be a result of wetness seeping in through basement windows, the walls, or the floor.

Give the basement the sniff test. Excess moisture causes an unmistakable musty or damp smell. A sump pump sitting quietly in a corner is a dead giveaway, too. It's not a decoration—it's there because the seller has regularly pumped water out or had a dampness problem at one point in time.

Some other tells might not jump out at you—you might not even realize what you're looking at—but they're nonetheless pretty reliable indicators that a basement has been wet or damp at some point in time.

Moldy Spots or Streaks

Look for mold. It might be black, brown, yellow, or green. You won't know for certain if it's mold until you have it tested, but it doesn't exist in a vacuum. It occurs relatively quickly after exposure to water, within 24 to 48 hours. It will bloom from there, thriving if left unchecked.

The northwest corner of a house is known as a "cold corner." It's often susceptible to developing mold.

Signs of Efflorescence

Efflorescence—a French term that translates loosely to "flowering out"—will produce a white or sometimes grayish ash on the walls. At first glance, it might appear chalky, but sometimes it sparkles. Efflorescence is caused by salt deposits left behind by evaporating water.

Surface Spalling

Salt deposits from the water can also cause surfaces to flake away, peel, or pop-off when it gets inside concrete, brick, or stone. This is referred to as spalling, and it occurs as moisture trapped within concrete tries to escape, particularly when its heated quickly.

Possible Causes of a Wet Basement

Groundwater can seep through floors and foundations due to freakish heavy rain or seasonal run-off, or the problem could be constant water seepage.

Gutters can overflow because of excessive rainfall, from clogging with leaves or debris or due to improper installation. Second-floor gutters might drain into the first-floor gutters. Gutters can also overflow if they're frozen, then suddenly thaw.

There might not be a sufficient number of gutters. Sometimes homeowners install them in one or two locations, but not all the way around the house.

Problems can be caused by disconnected downspouts, or by downspouts that aren't long enough to direct water away from the house.

Improper landscaping or grading can cause water to flow toward the house instead of away from it, and too much water can accumulate at the foot of the foundation and leak through if sprinklers are aimed toward the house.

Pipes will often form condensation and drip in high humidity areas, especially from air conditioner units that don't have a release valve.

It can provide a direct channel for water from the roof to seep into the house if the interior walls of the home lead directly from the attic to the basement.

Possible Solutions

You have several options for remedying a damp or wet basement, particularly if the problem isn't severe.

Redirect the Water

Redirect the source of the water. This sounds simple, but it's often overlooked. You can take care of this in a few ways.

  1. Reconnect disconnected downspouts
  2. Redirect second-floor gutters to separate downspouts
  3. Increase downspout efficiencies by attaching extensions designed to move water downhill
  4. Turn sprinklers away from the house
  5. Clean out the gutters
  6. Install flashing on the roof and under window sills
  7. Regrade the landscaping to slope away from the house

Install French Drains

You can do this either under the slab or around the house, along with a drain tile.

  1. Dig a two-foot hole around the perimeter that's at least six inches wide
  2. Attach a waterproofing membrane to the house
  3. Line with clean rocks
  4. Lay in a four-inch perforated pipe with the holes up
  5. Backfill with rocks
  6. Replace the top layer of soil or sod

Install a Sump Pump

Install a sump pump in the basement. The pump will send the water to the street, or at least 20 feet or so away from the foundation. You'll also want to tuckpoint the exterior and interior walls. This involves removing deteriorated mortar and replacing it.

  1. Clean out old mortar and cracks
  2. Fill with fresh mortar
  3. Let everything dry
  4. Cure by spritzing the joints with water daily for the first week

Use a Dehumidifier

A dehumidifier can help a great deal if your problem isn't severe—your basement is more on the damp side than out-and-out wet. Most dehumidifiers simply absorb moist air, while others go a step further and refrigerate or chill it to a liquid state that can drip off.

Install a Floor Drain

Install a floor drain and insulate the walls. Waterproofing by painting a sealer on the interior walls doesn't really help much if water is putting pressure on the walls. It will just leak through eventually.

Some Simpler Fixes

  • Check dryer vents and seal them with foil—not duct—tape
  • Make sure your pipes are insulated and keep windows closed during humid and damp weather
  • Check your foundation for cracks or holes, and plug any that you find
  • Consider painting your walls with waterproof paint or another waterproof sealer

Final Precautions

Don't store valuables, photographs, paper documents, or anything you want to preserve in a wet basement.

Get an expert's opinion, including an engineer's report, before you buy a house with a basement. It might not be worth the hassle if it turns out to be damp or wet.

Article Sources

  1. FEMA. "Dealing With Mold and Mildew in Your Flood-Damaged Home." Accessed April 23, 2020.

  2. International Association of Certified Home Inspectors. "Efflorescence for Inspectors." Accessed April 23, 2020.

  3. Portland Cement Association. "Types and Causes of Concrete Deterioration." Page 11. Accessed April 23, 2020.

  4. Consumers' Checkbook.org. "How Water Gets Into Your Basement." Accessed April 23, 2020.

  5. National Park Service. "A Glossary of Historic Masonry Deterioration Problems and Preservation Treatments." Page 61. Accessed April 24, 2020.

  6. National Storm Damage Center. "How Basement Dehumidifiers Work Their Magic." Accessed April 23, 2020.