How to Keep a Damp Basement Dry

Written by dannah swift
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Damp basements occur for many reasons. Surface water can collect around the foundation after a rainstorm. Groundwater can leech into the basement from beneath the floor. Improperly sealed ducts from heating and cooling systems or clothes dryers can release air into the basement, causing condensation and high humidity. Controlling humidity and dampness can mean construction of a French drain or simply using a dehumidifier in humid months, depending on the moisture level.

Skill level:
Moderately Challenging

Things you need

  • Waterproofing contractor
  • Plastic sheeting
  • Dehumidifier

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    Surface Water

  1. 1

    Eliminate the affects of surface water by locating the source. Examine gutters and downspouts during a rainstorm and make sure they are rerouting water as they should be. If you notice pooling around the foundation, install concrete splash blocks where spouts discharge and pitch them to direct runoff at least 6 feet from the foundation.

  2. 2

    Grade all landscaping away from the house and the foundation. Water build-up in root systems is another source of water damage to the foundation.

  3. 3

    Protect window wells at ground level by sealing around the windows. Prevent water from accessing the window well by installing a plastic bubble-like cover over the top. Find them at your local home improvement retailer.


  1. 1

    Dig----or hire a waterproofing contractor to dig----a French drain around the perimeter of your basement. Applying a waterproofing sealant to the interior of your basement walls is not a sure fix; sealants can seal water inside the foundation where it can do more damage.

  2. 2

    Dig a trench, 12 inches deep and 12 inches wide, along the perimeter of the basement. Your trench should reach the bottom of the foundation footing.

  3. 3

    Tap the wall by drilling small holes in the concrete and allowing the water to drain into the trench.

  4. 4

    Lay perforated, 4-inch pipe in the trench. Cover it with gravel; cover that with cement, leaving a 3/4-inch-wide track between the drain and the wall to collect what the drain might miss. French drains connect to a sump pump via a feeder drain.

  5. 5

    Install a sump pump to lower the water table----the level below which the ground is saturated with water----only if there is already excellent drainage beneath the cellar floor, such as gravel.

    Prevent Humidity

  1. 1

    Prevent condensation build-up in your basement----which leads to mould and other bacteria growth----by making sure your dryer vents are completely sealed.

  2. 2

    Examine any heating or cooling ducts in your forced air systems for holes or other leaks. Make sure connections at vents and registers are well-sealed where they meet the floors, walls, and ceiling.

  3. 3

    Use a dehumidifier in the humid months of the year.

Tips and warnings

  • You might also consider installing a rain barrel. Rain barrels collect rain water from downspouts. This way, the runoff does not get a chance to penetrate your basement walls, and can be used to water gardens and lawns without tapping the public water supply.

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