How to Waterproof a Basement

Written by Anita Alvarez
Updated December 17, 2019
French drain in basement
A French drain is one possible basement waterproofing solution. (Photo courtesy of Angie's List member John O. of Lawrenceville, New Jersey)

A good waterproofing contractor can find the best solution for your basement.

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How much does basement waterproofing cost?

Sump pumps or dehumidifiers will run a few hundred dollars. Major solutions such as drainage systems are likely to coast between $5,000 and $15,000.

From poor construction practices to damage to wear and tear, a leaky basement poses significant problems for homeowners. Even a small basement leak can be a hassle, and a flooded basement can be a nightmare to deal with. Having to deal with moisture in the basement, repeated flooding, and paying to replace damaged items often motivates homeowners to search for a comprehensive solution, and turn to basement waterproofing

A good basement waterproofing job can prevent mold, get rid of mildew, and ward off a musty smell in basement. Plus, the moisture, mold and mildew can lead to poor indoor air quality or health problems in the home, so you want to get rid of the damp basement quickly. 

DIY basement waterproofing is not recommended by professionals. You can handle basic tasks like applying epoxy or sealants without too much trouble, but any serious, in-depth work, such as installing a French drain and sump pump or waterproofing basements from the outside — all of which require excavation, concrete cutting or both — should be left to the professionals. Waterproofing basement walls from the inside is the only task a homeowner should seriously consider undertaking themselves. 

1. Determine the cause of the basement flood or leak

Obvious basement problems are easy to diagnose when the area floods, or at least a few inches of water accumulates on the basement floor when it rains or storms. However, more subtle signs of moisture problems include mold on the walls or items stored in the basement, moist or damp walls, cracks in the walls, and puddles of water on the floor. Dampness in the basement may not be as obvious as basement flooding, but it can be nearly as damaging in the long term.

2. Determine if you need to hire a basement waterproofing professional


The right waterproofing solution depends on a number of factors, such as the whether the source of water comes from cracks in the walls or an improperly installed foundation. As mentioned above, it is strongly recommended that you do not undertake this on a DIY basis but rather hire a reputable basement waterproofing contractor to diagnose the problem and recommend the right solution. Some basement waterproofing techniques include:

Sealants. A variety of sealants can be applied directly to the surface of your basement wall, including basement waterproofing paint, epoxy, crystalling sealant, or sodium bentonite waterproofing products. A professional can guide you as to the best methods — and indeed most will guide you away from paint — but it is possible to use these methods on a DIY basis.

Tanking. Wrapping the outside of the basement with a sealant, tanking is most often used when the basement is accessible from the outside, and it effectively wicks water away from the surface to prevent penetration through the walls. If the construction of the basement failed to use the tanking method, your basement contractor may recommend excavation in order to access the walls.

Interior drainage. Often used in areas where heavy rains aren't an issue, installing a cavity drainage system involves employing a membrane on the floor and walls of the basement, effectively "wrapping" the space in an envelope to prevent water infiltration, along with conduits for drainage and a pump—usually a sump pump. This methodology will only work if your foundation already slopes toward a drain. Otherwise, the costs to grade the floor to slope toward the drain are often too high to deem the project cost-effective. This system should generally be powered by a backup sump pump, or flooding could still be a problem should the power go out.

Exterior drainage. Most often employed in areas where heavy rains are common, exterior drains in the foundation prevent water from moving through the concrete walls. In effect, a series of pipes are laid down directly outside the basement, eventually connecting and leading to a drain located far away from the home. Many of these solutions will also protect your foundation, possibly avoiding a costly foundation repair job in the future. 

Unless you have personal experience and feel qualified to use any of the advanced methods, hire a professional. If you want to apply waterproofing sealants on a DIY basis, read on.

3. Determine which waterproofing sealant you want to use

Different basement waterproofing sealants address different problems. Epoxy and sodium bentonite waterproofing methods, for instance, are best applied to cracks, while crystalline waterproofing is applied directly to the surface of an existing concrete wall. Be aware that crystalline waterproofing can only be applied to bare concrete; it won't work on a previously sealed or painted wall. Once you've determined the best solution, purchase your materials at a hardware store. 

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