Exterior Waterproofing Compounds for a Cinder Block Foundation

Concrete Block Issues

• Cinder- or concrete-block foundations are problematic because of the mortar joints. When these foundations are damaged, it is almost always at their joints. It is the weak spot of that foundation type. The porous nature of the block, as well as the mortar joint itself, makes this foundation type prone to water damage and seepage. In general terms, there are three specific compound types on the market: liquid seals, epoxy seals and polymer seals. The type of product you buy depends on many factors. However, if water seepage is damaging your basement, a quality sealant is only part of the story -- better drainage should also be a part of reforming your basement structure. A sealant cannot normally do the job on its own.

Rubber Membrane Liquid

• Several firms use a liquid membrane that dries to a rubber finish that is impenetrable. The liquid can be sprayed on the block or applied with a brush or roller. It is a dark brown compound that, after about 10 minutes, cures to a highly flexible rubber coating that bonds very well with concrete block. It goes on at a thickness of about 60 millimeters, and dries to about 40 millimeters. It waterproofs the basement as well as seals it against radon and termites.

Epoxy Hydrophilic Sealants

• Specifically for cracked concrete, this flexible grout is perfect for the weak spots of blocks -- their mortar joints. The sealant here is not specifically for total coverage, but seals cracks and other damaged parts of the block. When applied to the cracked joint, it expands to seven times its original volume, filling every nook in the crack creating a flexible joint. It must always be applied with water.

Concrete Polymer Nano-Sealer

• A concrete polymer nano-crystal sealant is highly effective for concrete in wet and hot environments. This is a liquid that is spread on concrete or cinder block. It penetrates the block and reacts with the lime in the cement. This reaction creates millions of microscopic nano-sealant crystals that are formed to completely seal the concrete. It blocks the pores of the material completely and, as a result, it increases the strength of the block by about 10 percent, creating a far harder exterior.