Waterproofing for Exterior Foundations

Choosing the Right Product

• There are many waterproofing and water dampening products on the market, overwhelming consumers with various choices. Dampeners are not suitable for foundation masonry, often containing asphalt as the primary ingredient. After drying, asphalt becomes brittle and can crack, allowing water to penetrate. Waterproofing products have urethane, latex or modified asphalt ingredients to seep into the porous foundation and create a barrier against water penetration. Read the label or talk to a masonry expert about getting the right product for your waterproofing needs.

Application of Waterproofing

• The foundation should be clean and free of any dirt or debris. If the foundation was not recently poured, cleaning it with a mixture of trisodium phosphate or another similar solution will remove caked-on grime, dirt and grease. Once the foundation dries from the cleaning, spray waterproofing sealer on in a smooth, consistent coat. You can also use a paintbrush, roller or towel application, though this is more time-consuming and labor-intensive. Let the sealer dry, and apply a second coat. Allow the sealer to set for 72 hours. Drizzle water on the surface to see if the water pools or is absorbed. If it is absorbed, you may need another coat to effectively seal the surface.

Considerations

• Sealing a foundation is sealing in anything already in the porous material. If you have an unsealed foundation that has dirt, cracks, pet stains and anything else daily living can throw at it, make sure you properly clean it. Repair cracks and make sure there are no drainage issues causing water to seep up into the concrete. A freshly poured concrete foundation needs 90 days to cure before you seal it, allowing the water content to evaporate slowly, creating a stronger foundation.

Other Waterproof Issues

• Sealing the concrete is only part of waterproofing your foundation. Check all landscaping around the foundation to ensure proper drainage happens away from the slab. Waste pipes and leach beds should be at least 3 feet from foundation perimeters. Water issues coming from under the foundation resulting from poor or improper drainage can result in foundation cracks or even failure.