APPLY a masonry waterproofing product to the bare interior walls of the basement. If the foil test showed that water penetrates through the basement walls and leaves them damp, seal the inside of the walls with high-quality waterproof paint, such as DRYLOK White Extreme waterproofing agent (available at Home Depot). The “wrapping” principle can also be applied to keeping a basement dry. A very effective method of waterproofing basements is to “wrap a basement, fully or partially, with an outer waterproofing membrane”.
Of course, such a membrane is created by coating a wall with asphalt modified viscous polyurethane and not covering it with laminated products, but when the membrane cures it forms an envelope on the outside anyway. Exterior waterproofing generally requires excavating the soil that surrounds the foundation of the house. As you can imagine, this can be a labor-intensive process that requires heavy tools and machinery. Once all the soil around the base has been removed, an impermeable sealant can be applied to the outer walls.
This sealant is usually a polymer base, which must last the entire life of the building. Ideally, this exterior waterproofing process should occur during construction. While it's often tempting to save money now by ignoring the problem, waiting to fix basement waterproofing can lead to much higher bills in the future. If this sounds all too familiar, you might be wondering what the best ways to waterproof basement walls are and if you can do it yourself or if you'll be forced to call a professional.
The best way to waterproof basement walls by hand is to fill the cracks with hydraulic cement (it opens in a new tab) and apply a sealant designed to waterproof the basement walls, in addition to using silicone masonry putty around the window jambs. Fix it with a portable dehumidifier for rooms or a humidification system for the whole house instead of waterproofing products. Indoor waterproofing methods, such as waterproof sealants, also help to keep humidity levels low and prevent condensation. The statements of the manufacturers and the anecdotes of the owners about successful interior waterproof solutions for basement walls and slabs did not quite add up.
However, here we will focus on interior waterproofing that you, as a homeowner, can do yourself to achieve a dry basement. Many waterproofing service companies offer a free inspection to determine the extent of damage and the cost of repair services. Waterproofing can be a key element in realizing your favorite basement ideas, but unfortunately, not everyone does it until it's too late. Hydraulic cement and putty are popular options for DIY attempts to waterproof a basement from the inside.
Many of the waterproofing products listed below will only work if applied directly to the substrate, so if there is any existing coating on the surface, wall, or floor, it must be removed. Negative side waterproofing (NSW) is a difficult subject that, frankly, I've been dancing about for quite some time. Hammer and Hand (a builder based in Portland, Oregon) generously offers and thoroughly details its existing basement approach here.