Tools & Tips: Damp Proofing Basements

From on April 28, 2008 in Tools and Tips

With spring in full swing and subsequent rainfall and melting snow, it is important to double check the seal or water resistance of your home. Foundations, while they may appear dry and waterproof, are in fact very absorbent of water from moisture in the soil outside or underneath your basement. Water is absorbed through untreated concrete and evaporates inside the basement. Often, the walls will appear dry but in fact are transmitting water and giving your basement that “damp” feeling.

In newer basements a water vapor barrier should already be installed beneath the concrete slab floor, but this barrier is often overlooked outside basement walls. The best way to waterproof a basement is to have it done on the exterior of the foundation walls prior to construction. Yet many contractors dismiss this step in the process because of higher initial costs and most basements are not sealed without specific homeowner request.

Waterproofing basement

If you have problems with dampness in your basement it may also be due to improper grading (grades should slope away from your foundation for at least five feet), improper drainpipe installation which will leave water near the foundation, or a lack of gutters. You should address any of these issues if you can as they will compromise any damp proofing you do inside your basement. Here are some ways to waterproof a basement.

Damp proofing is especially necessary if you plan on finishing the basement and making living space out of it. There are several ways to damp proof your basement. The most common is to apply a concrete waterproof sealer directly to the basement walls. There are several brands and they usually come in a powder form, which you then mix with water to the proper consistency and apply with a long bristle brush. These solutions will get into the pores of the concrete and create a waterproof crystalline barrier to block moisture.

If you have cracks in your walls or floor then you will need to address these before applying any damp proofing agent. You can take care of cracks by chiseling them out to around 3/4” deep and wide and then patching them with a concrete material.

Spring is a great time to test your basement for dampness. You can do this by putting a piece of tape or plastic on your wall or floor and leave it there for a few days. If, when you return, you find moisture underneath the plastic or tape, then you have moisture issues which should be taken care of.