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Home > Projects & DIY Toolkit > How-To Articles > Preventing Leaks in Your Basement

Preventing Leaks in Your Basement

Leaks and dampness can be intimidating and worrisome, but there are things you can do yourself to alleviate the problem. Your situation probably can be improved by addressing drainage problems, repairing leaking cracks or holes, and incorporating the use of waterproof sealers. If you find that you still have a problem after performing these suggestions, you should seek help from a professional waterproofing contractor. Lowe's is happy to provide this information as a service to you.

Tools & Materials

  • •Hydraulic cement
  • •Caulking
  • •Chisel
  • •Drilling/engineers hammer
  • •Goggles
  • •Brush
  • •Rubber gloves
  • •Spray bottle
  • •Trowel

How Serious Is It?

A small percentage of basement water problems are the result of underground water levels. When the water table rises above the level of the basement floor, the water is constantly applying pressure, trying to get in.

Serious basement water problems caused by high groundwater levels require serious prevention measures. Drains can be installed around the inside perimeter of the walls, and sump pumps can be installed to actively pump the water outside. These fixes may keep the house from floating away, but the presence of water in the basement, even as it is being drained or pumped away, is still going to raise the humidity in the air.

One of the most difficult and effective fixes for serious basement water problems involves excavating around the home's foundation, applying sealer and drainage board to the foundation walls, and running drains along the foundation footing to carry water to a storm sewer or distribution field. It is unlikely, however, that these are jobs that a do-it-yourselfer would want to attempt.

Fortunately, most basement water problems are the result of surface water and roof runoff. These problems are much less serious, and homeowners can go a long way toward solving the problem themselves. The primary concern when attempting to prevent moisture from entering your basement involves directing water away from the foundation. Doing so reduces the pressure placed upon existing sealing systems which are already in place.

Roof Water Blues

The first place to start when trying to tackle a basement water problem is your home's eavestrough system. Unless it is properly channeled away from your home's foundation, all that water collected by the roof can quickly saturate the ground surrounding the basement walls. This is a recipe for a wet basement, regardless of any attempts you may make to seal it from the inside.

Stopped up eavestroughs create problems by forcing water to run over their sides and down to the ground, possibly damaging eaves and fascia boards in the process. Leaking eavestroughs concentrate waterflows at the leaks, eroding the ground and dumping water right next to the house. Make sure your eavestroughs are clean and in good repair.

Direct all downspouts away from the foundation. Splashblocks help prevent erosion, but they do not channel water very far away from your home. Better results can be achieved by connecting the bottom of the downspout to a 6 foot or more eavestrough extension. Corrugated plastic pipe works well for this purpose. These pipes can sit on top of the ground and empty into splash blocks, or they may be buried and run to underground drains or runoff areas.

Caulk any cracks between driveways, concrete slabs and your home's foundation with a 100 percent silicon sealer. Check these areas at least twice a year. This sealer serves two very important purposes. First, it prevents water from channeling through cracks into areas you would rather keep dry. Second, it prevents water from getting into the cracks and freezing, thereby widening the crack and making the situation altogether worse.

The Draining Game

The ground around your house should slope away from the foundation. Sometimes, after the ground around new construction has time to settle, it will sink and slope toward the house. In this situation, when surface water collects during rains, it accumulates around your home. Your house is left sitting in a puddle - a situation not very conducive to a dry basement. If you have enough exposed foundation, you can build a slope up to it around the house. Otherwise, grade the area within 6 feet or more of the house to slope downward and away from the foundation. Try to make the grade slope 2" per foot for the first 4' or more and 1" per foot thereafter.

Homes built on slopes that experience severe runoff may require a drainage system. An underground drain should be installed in the area where the grade leading away from the house meets the slope. In this case, make sure that the grade meets the slope at least 6' from the house. The drain can be constructed of perforated pipe placed near the bottom of a bed of crushed stone. On top of the gravel should be layers of filter fabric, sand and soil. Grass is sown in the soil, making this type of drain invisible except for a gentle trench above the drain. This gentle depression collects the water and gives it time to trickle through to the pipe, which carries it away from the house.

Repairing Leaky Cracks in Masonry Walls and Concrete Floors

If you have cracks in your basement that allow water to leak through, you can cure the problem by using a special hydraulic cement. Like other types of cement, quick drying hydraulic cement comes as a powder which is mixed with water. It dries very quickly, even under water, and can be used to patch cracks in masonry and cement to effectively seal out water.

Leaky cracks should be fixed as soon as possible, since any water that freezes in those cracks will expand and cause further damage. If a crack reopens after it is repaired, you may have a serious problem. Consult a building professional.

To patch cracks in masonry walls or concrete floors, do the following:

  • 1.Use a cold chisel and heavy hammer to open up the crack. Undercut the inside of the surface (make the inside of the crack larger than the outside) so that as the hydraulic cement cures, it will expand and become "keyed" or locked in place in the crack. If you are fixing a crack in a block wall, do not go deeper than 3/4" or you may burst into the hollow part of the block.
  • 2.Using a brush, clean the area to be patched, removing dust and debris.
  • 3.Mix the hydraulic concrete per the instructions on the label.
  • 4.Dampen the area to be patched with water. A spray bottle like those used for glass cleaner would help do the job easily.
  • 5.Fill the crack with hydraulic cement to within 1/2" of the surface. After this first layer dries, smooth in a second to the right height to match the surface you are repairing.
  • 6.If water is entering through the crack at the time you are making the repair, trowel in the hydraulic cement and hold it in place with the trowel or some other flat surface for 5 minutes while the cement hardens.
Be sure to wear safety goggles! Flying chips of concrete or masonry can cause serious eye damage.

Sealing Your Basement Walls and Floor

After all cracks are repaired and any drainage or leakage problems have been addressed, you may wish to waterproof the walls of your basement to seal out unseen moisture which could otherwise enter through the porous block and concrete surfaces.

Several different products are available to do this. Some waterproofers are powders which must be mixed with water. Others are ready mixed, cement-based oil or latex formulations.

The walls must be prepared before painting to remove dirt, dust, grease, loose mortar and "efflorescence" - powdery salt-like deposits that build up on the surface. You may be able to scrub the walls with water, mild detergent and a stiff (but not steel) brush. Or, to ensure adequate adhesion, it may be necessary for you to "etch" the wall with muriatic acid or some other commercially packaged etching compound. Concrete and masonry etching products can be caustic, so follow the directions on the product and keep safety in mind. Rubber gloves, goggles and adequate ventilation are a must.

After the walls are sealed, concrete floors can be sealed with heavy-duty water-based polyurethane. This finish has several advantages. It is a low odour product which can be cleaned up with water. It also dries quickly, allowing you to recoat within a couple of hours after application. It can be easily applied with a painting pad on a roller extension pole.

If the floor has a rough finish, apply the polyurethane with a broom. Run it a couple of inches up the walls around the perimeter of the floor to assure a good seal where the floor and walls meet. Apply three or four coats, recoating according to the product application instructions. Then allow the floor to cure for several days before using it.

Tools, products, materials, techniques, building codes and local regulations change; therefore, Lowe's assumes no liability for omissions, errors or the outcome of any project. The reader must always exercise reasonable caution, follow current codes and regulations that may apply, and is urged to consult with a licensed professional if in doubt about any procedures. Please visit our terms of use.

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