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 intrude, 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. It can find its way into a basement over time.

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 afterward, 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. They might gamble that it will be difficult to prove in court that they knew about the situation, or they might figure that it will take years for the matter to get to court—if you even sue at all. Lawsuits can be mighty expensive.

But it can also 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 simple, such 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 can cause an unmistakable musty or damp smell.

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 mold shouldn't exist in a vacuum. There should be other signs as well.

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

Efflorescence will produce a white or sometimes grayish ash on the walls. Sometimes this ash sparkles. Efflorescence is caused by salt deposits left behind by evaporating water.

Salt deposits from the water can cause the surface to flake away, peel, or pop-off when it gets inside concrete, brick, or stone. This is referred to as spalling.

A sump pump sitting quietly in a corner is a dead giveaway. It's not a decoration. It's there because the seller has regularly pumped out water or had a dampness problem at one point in time.

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. For example, the 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 if sprinklers are aimed toward the house, too much water can accumulate at the foot of the foundation and leak through.

Pipes will often form condensation and drip in high humidity areas, especially from air conditioner units without 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: Redirect the Water

Redirect the source of the water. This sounds simple, but it's often overlooked.

  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.

  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.

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

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

The Bottom Line

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 wet basement. It might not be worth the hassle.

At the time of writing, Elizabeth Weintraub, CalBRE #00697006, is a Broker-Associate at Lyon Real Estate in Sacramento, California.