Concrete blocks have been used for many years as the alternative to a poured concrete foundation wall. Since concrete blocks are porous and concrete block foundations have numerous joints, they can be prone to water leaks. This is why waterproofing this substrate is so critical for the long-term performance of a concrete block foundation. On the positive side, they are strong, and have some thermal and sound insulation properties, which reduces energy usage. They are fire-resistant, and the addition of rebar adds structural strength to the foundation. Concrete block foundations are well suited to seismic areas, e.g., areas that are earthquake prone, like California. Concrete block building foundations also discourage rodents and termites.
Because of the concrete block’s porous nature, they are susceptible to moisture intrusion. This can ultimately cause damage to the foundation, or leaks into the occupied space. Additionally, you have to protect your mortar joints, because they are the vulnerabilities in your concrete block foundation. They can crack from soil movement or water pressure over time. Once they crack, this creates a new pathway for moisture to travel through and wreak havoc on your building foundation, and then your entire building.
So, how do you prevent this from happening? By using a waterproofing membrane that addresses the limitations of a concrete block foundation and prevents moisture intrusion. This article explains which materials you can use, as well as the protocols for waterproofing a below-grade concrete block foundation.
Which products can I use to waterproof below-grade concrete block foundations?
- LIQUID RUBBER: Today’s rubberized asphaltic membranes are a big departure from materials used in the previous century. Now the formulations are highly blended, emulsified asphalt, mixed with polymers to provide long-term performance. The addition of these polymers allows for a more durable, elastic material. Cold-process, fluid-applied, asphaltic-rubber membranes are LEED-compliant materials designed to waterproof foundations with irregular surfaces, foundational movement, and the expansions and contractions you would anticipate from drastic weather changes. They easily adhere to everything, displaying good vibration absorption, shear, and peel strengths
- SELF-ADHERING MEMBRANE: These waterproofing membrane sheets come in rolls comprised of a polymer-bitumen material that already has a factory-controlled thickness. The nice part is they are already fully cured, which reduces the lag time in your project timeline between membrane application and backfilling.
For this article, we’ll assume you’re waterproofing a newly constructed, below-grade concrete block wall.
The 7 Steps to Prevent, Preserve, and Protect Your Concrete Block Foundation:
- THE MAGIC WAND FOR YOUR BOND: You need to remove any contaminants on the surface of your concrete blocks. Dust, dirt, and debris will affect the strength of your waterproofing membrane’s bond. This will give you a better surface for adhesion, while also preventing and protecting your foundation from moisture intrusion. Prior to installation, the surface needs to be dry, free of frost, and relatively smooth.
- FRACTURE INFRACTIONS: Before you start concrete-block wall waterproofing, fortify every void, joint, and crack on your concrete block’s surface with hydraulic cement or masonry caulk. Once you’ve applied this material, you’ll need to give your joints, cracks, and voids 24 hours to dry before you move on to the next phase of your waterproofing protocol.
- TO PREVENT A MESS, PRE-ASSESS: Before you select a waterproofing membrane and system, it is critical that you understand where the water table is and the fluctuations that can occur throughout the year. First, assess your location situation, review the materials, and design the best system to give you long-term performance.
- MEMBRANE YOUR DOMAIN: Selecting the right waterproofing membrane is critical. Both sheet-applied and fluid-applied membranes can be applied onto a concrete block foundation, with great performance characteristics. However, there are also some limitations. Review all of these limitations when you are in the mode of selecting your product. REMEMBER: If you select a sheet-applied product, you must apply a primer/adhesive to prepare your concrete block foundation to create the solid surface your membrane will need to adhere to it properly.
- SATISFY VIA FLUID APPLY: Your other option is a fluid-applied membrane. When you’re sealing below-grade concrete blocks from moisture, and you’re not facing an issue with a too-close-for-comfort water table, a cold fluid-applied asphaltic rubber membrane is your best product solution for sealing your below-grade concrete block walls. This category of products is flexible and adheres to every type of substrate. Fluid-applied rubber membranes apply easily with a brush, roller, or trowel. There are also spray-grade materials, but these do require specialized equipment and a trained contractor. Fluid-applied membranes give you a monolithic membrane. Depending on the material you choose, the recommended applied thickness will vary. Once you’ve applied your below-grade concrete waterproofing membrane to the desired thickness, you’ll want to give it 24 hours to fully cure before moving on to the next step.
- TAKE PAINS TO DRAIN: You will need to install exterior drainage boards and footing drains to extend the life of your freshly waterproofed, below-grade concrete block wall as part of a complete waterproofing system. In most areas of North America, the hydrostatic (water) pressure is endless, forever seeking pathways to invade your building foundation, so having this drainage layer ensures lasting protection. Once your waterproofing membrane system is fully cured, you’ll install a prefabricated dimple membrane drainage system over the applied membrane.
- BACKFILL TIME IS SUBLIME: There’s nothing more satisfying than that moment you start backfilling your foundation, confident in the job you’ve done and that you’ve protected the structure and its future occupants from the damages, health hazards, and heartbreaks caused by moisture penetration. This moment in your arduous waterproofing process is the celebratory end cap to a project well done.
To learn more about how to waterproof your below-grade concrete block foundation, feel free to call our friendly, helpful inside sales team at 1-800-342-5976. For information on W. R. MEADOWS below-grade concrete block waterproofing products, please click here.
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