How To Waterproof Your Basement

Roger Diez | Improvement Center Columnist | December 13, 2011

If you reach the bottom of your basement stairs and your feet get wet, you have a problem. There are many causes of a wet basement and the solutions range from simple and cheap to complicated and expensive. Depending on the diagnosis of the problem, it may be a job for a handy homeowner, or for a trained professional.

What causes a wet basement?

There are three main causes of water in the basement: a plumbing leak, condensation or seepage. Of these, the plumbing leak is the easiest to fix once you find it. The second, condensation is also relatively easy to fix with a few simple steps. The third, seepage may have a simple solution, or it may be complicated and costly. Troubleshooting will indicate which condition exists. For instance, if your basement is wet only following a heavy rain, standing water next to the house may be seeping through the foundation.

How to waterproof a basement

In the case of rain-related leakage, try extending your downspouts to channel water away from the foundation. This works a large percentage of the time. If the dampness is fairly constant, but there is no standing water in the basement, damp-proofing techniques may work. These include applying a sealant to either the inside or the outside of the basement walls. Cementious coatings, asphalt coatings, acrylic or polymer sealers, and even polyethylene sheeting have been used effectively. Some may require excavation, and the sheeting can be applied before a new slab floor is poured over the old one.

If damp-proofing techniques don't work, it's time to bring out the big guns. More aggressive coatings made of combinations of asphalt, rubber and urethane applied by professional contractors skilled in application techniques may work. Mechanical systems, such as adding drains and sump pumps may also be helpful. There are even homeowner-installed baseboard drain systems that have proved effective.

Cost of waterproofing a basement

For condensation problems, insulating pipes will run around $50, and a good dehumidifier will cost $300 or more. Downspout extensions cost only a few dollars, but if other gutter system repairs are needed the cost could increase to $200 and excavation to improve drainage could increase the cost even more. Professionally applied coatings start at around $350 and increase from there, while installation of drains and a sump pump may run from $1,000 to $2,500. If foundation repairs and excavation to install an outdoor drainage system are required, the cost could easily exceed $10,000.