Finishing a Basement 2 - Moisture Proofing
No one wants to spend time in a damp, cool basement. If your basement has water problems, or even if it is just a little damp and moist, you'll need to deal with the moisture before doing anything else. Even if you think your basement is dry, test it to be sure.
To test your basement for moisture, tape a piece of plastic or tin foil onto the basement floor. Seal around the edges and leave it for several days. If you get moisture on the exposed surface, then the problem is condensation. The insulation and ventilation in your finished basement will correct the problem; however, if you have moisture under the plastic, you have some seepage through the cement.
Often, moisture in a basement is simply a matter of poor drainage outside the house. It could be caused by any combination of lack of gutters, bad grading, or an incorrectly placed drainpipe that leaves water near the foundation. Water should be directed at least 5-feet away from the foundation walls. Fixing these areas will keep dampness out of your basement.
Concrete waterproof sealer can also be applied directly to the walls and floors. There are a number of different brands available at your home store, but most come as a powder that's mixed with water, then applied with a long bristle brush. Keeping the sealer moist so it dries over a period of days allows it to actually get into the concrete pores and form a waterproof crystalline structure that blocks moisture.
Obviously, any cracks in either poured walls or concrete block walls need to be repaired as well. Hairline cracks should be chiseled .75-inches deep and wide, then filled with a concrete patching material. Any cracks in the floor should also be chiseled and repaired with standard concrete and a bonding agent.