Products for the Treatment of Leaking Concrete Block Walls

Waterproofing and Sealing

• Sealers are designed to repel water, but a true waterproofer actually stops the flow of moisture through a concrete wall. The product that is ideal for your wall typically depends on the condition and location of the wall and the amount of moisture leaking through. Products that seal or prevent leaks can be categorized as two main types. Penetrating waterproofers like silanes and siloxanes are chemical sealers that react within the capillaries of the concrete to block moisture. Typically, these are invisible and used to protect exterior concrete block walls from corrosion and damaged related to the freeze-thaw cycle. The second type are film-forming sealers, which are commonly used with interior decorative concrete. These products are sealers that form a film on the surface of the concrete wall that protects the surface and blocks moisture.

Silane and Siloxane

• Silane-based waterproofers penetrate concrete more effectively than so siloxane products, but siloxanes tend to perform better at resisting moisture and beading. Application of both types of waterproofing product requires a dry surface. This means that for exterior concrete walls, a period of at least 24 hours with sunshine and no rain is necessary to ensure a completely dry wall. The concrete itself must be at least 28 days old as well.

Acrylics

• Acrylic-based sealers are available in both water and solvent-based formulas and are typically used to treat exterior concrete walls. This type of film-forming sealer is UV-resistant and offers protection against leaks as well as chlorides used in ice-melt products. Acrylics are thinner than other sealants, which means they tend to wear faster and require frequent applications.

Polyurethanes

• Polyurethane sealers are formulated as water- or solvent-based and are thicker than acrylic sealers. They provide resistance to water, chemicals and abrasions. However, if your concrete block wall has significant moisture leaking through, polyurethanes may not be ideal. They’re unable to withstand moisture until they cure, so if water is present on the surface of the concrete when a polyurethane product is applied, a chemical reaction can occur that results in foam and bubbling.

Epoxies

• Epoxy-based film-forming products bond well to concrete and dry to a hard, durable finish. They’re available in clear or colored formulas, but tend to yellow due to UV exposure, so they aren’t typically used on exterior concrete walls. Epoxies provide excellent moisture protection, but some epoxy sealers are impermeable, which can result in moisture getting trapped within the concrete. If this is a concern, make sure to select an epoxy product that is labeled as permeable so that the concrete can release moisture or vapor if necessary.

Considerations

• Exterior surfaces require a sealer that is breathable to allow moisture to escape the concrete. Inside, this may not be necessary. Impermeable epoxies can be used on these surfaces as long as the exterior is not covered by a barrier that prevents moisture from escaping. When sealing indoor concrete block walls, a water-based sealer may be the better choice because it is safer, particularly if the area of application isn’t adequately ventilated. Solvent-based formulas are flammable, and sometimes the fumes are hazardous to breathe.