Basement Waterproofing: Water, Water Everywhere - But Not in Your Basement!

Using a quality water-proofing coating is a key strategy. However, take note: Even the best waterproofing coating may fail to stop moisture if the block walls are not in sound condition. Brush away loose mortar and broken block; remove dirt, grease, dust and other surface contaminants; wire-brush or sandblast old paint; use a quick-dry cement to patch cracks, holes and floor/wall joints.

Also, be sure to follow  manufacturer's instructions. The most frequent error customers make is failing to apply a waterproofing coating at the spread-rate specified by the manufacturer. If the coating is too thin, it will not stop moisture seepage. In cases of excessive water seepage, a second coat may be needed. During the application, the coating must be worked into the masonry pores.

Though some paint manufacturers use the terms interchangeably, water-repellent and waterproofing coatings are not the same. A water-repellent coating system is an exterior coating system for above-grade concrete or masonry. It temporarily repels water, but it is not intended to prevent the passage of moisture under hydrostatic pressure. Some repellents are film-forming; others act by filling surface pores to prevent moisture movement.

Waterproofing coating systems, on the other hand, are intended to prevent the passage of water under hydrostatic pressure. These film-forming coatings are formulated for above and/or below grade and for interior and/or exterior application.

Hydrostatic pressure may be caused by several conditions. Rain runoff flowing toward a house, high water table and faulty gutter systems are the most common causes of hydrostatic pressure on a foundation. Wind-driven rain is the most common cause of hydrostatic pressure on an exterior, above-grade wall.

Sometimes interior condensation can be mistaken for seepage due to hydrostatic pressure. To distinguish between the two, tape a piece of aluminum foil to the inside of the foundation wall. Remove the foil after several days. If the wall side of the foil is wet, seepage is the problem. If the room side is wet, condensation is the problem. (Both problems can occur at the same time.)

While a dehumidifier can solve the condensation problem, a quality waterproofing coating is needed to stop the seepage. Not all coatings are intended for waterproofing. Most acrylic latex paints, for instance, are not formulated for this job.

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