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Unless your plan is to install a swimming pool in your basement, you probably cringe at the idea of water trickling in beneath your house. While the best time to waterproof is during new construction, if you live in an older structure, you don’t have that luxury. There are, however, a few measures you can take to protect your home from water, running the gamut from inexpensive safeguards to high-dollar professional remedies. Here’s all the information you need to choose the best solution for your basement.
The most effective way to waterproof a basement is from the outside. Doing so, however, involves excavating the soil away from the exterior of the foundation on all sides and installing drain tile (a flexible perforated pipe covered with mesh or fabric) at the base of the foundation.
You’ll most likely need a permit before starting, and some building authorities will allow only a licensed contractor to do the job. Digging a 7- or 8-foot-deep trench around your foundation is dangerous; it comes with a high risk of collapse, so it’s usually better to seek out an excavation contractor who employs safe digging techniques and trench bracing, anyway. Timing is essential: Schedule your contractor during a relatively dry season, or you could end up with a trench full of water that will have to be pumped out before work can continue.
Drain tile also requires the installation of a sump pit where the water will collect before it’s pumped to the surface via a sump pump. You can choose to have a sump pit installed inside, beneath the basement floor, or outside the house, typically below a window well.
While the drain tile is being installed, you or your contractor should take this time to repair, patch, and seal the exterior foundation walls. Patch large cracks with a mortar-based product, and when dry, roll, brush, or spray on an exterior masonry sealant. All said, this is an expensive project that can cost upwards of $10,000, but it’s the surest way to stop the leaks.
Interior remedies can be helpful in the cases that leakage is minimal or if exterior excavation is out of the question. If you have fine cracks that seep slowly (or just look damp), your basement might be a good candidate for an interior sealant. Most interior masonry sealants work only on unpainted concrete walls—if your walls are painted, the sealant can’t form good contact and results are likely to be poor. Available in one- and five-gallon buckets, these sealants require a heavy-duty brush or roller to apply and can cost between $50 and $500 when treating 100 square feet of wall, depending on product quality and the number of coats that need to be applied.
If the walls have numerous or wide cracks, or if previous attempts to seal the walls were unsuccessful, you may want to consider installing an interior floor drain system. This process is similar to that of installing exterior drain tile, but excavation is shallow and confined to the inside perimeter of the basement floor. If you’re comfortable running a concrete saw and a jackhammer—and you have a strong back—you can potentially do this job yourself, although it’s labor-intensive and messy. Installation requires excavating a trench along the basement walls, filling it with pea gravel and perforated drain tile, installing a sump pit for water collection, and then filling in the trench with concrete so that a narrow grate is the only evidence that a drain lies beneath. Typically, plastic panels are installed over leaky walls to direct water downward to the grate. Installation of the trench drain, the sump pit, and the panels can run into thousands of dollars, but doing the labor yourself can save you a little cash.
Even if you don’t need to fully waterproof your basement, you should at least take steps to protect your foundation from water. Install gutters and downspouts, and attach downspout extensions that direct rainfall away from your house. If your yard does not already slope away from the foundation at a minimum 2 percent grade, bring in topsoil to build up the level of the soil around the foundation. Relocate foundation plantings that require frequent watering, and install waterproof window well covers on any basement windows that can’t be used for egress.
Water that pools by the foundation is always problematic. If you have clay soil that swells when wet, it can exert lateral pressure on the exterior foundation walls, increasing the risk of cracking and shifting. Frost heave during freeze-thaw cycles can also damage the foundation. Remember: Water and basements don’t mix. If you’re proactive in keeping water away from your foundation, you’ll have a better chance of keeping your basement, and the rest of your home, safe, and dry.