Brick sealant is a protective coating applied to exterior brick surfaces, such as chimneys, walls, or patios. Because brick consists primarily of natural clay, it tends to feature a highly-porous surface. As moisture seeps into the brick over time, it can lead to damage due to freezing or temperature changes. Brick sealant keeps water out and prevents cracks and other signs of damage, which not only impact a home's appearance but could potentially impact its structural integrity.
The moisture that contributes to brick damage comes from a variety of sources. Rain may soak into the brick, or the brick could draw natural moisture out of humid air. Air conditioning condensation or leaks may penetrate the brick from inside the home or out. Clogged or faulty gutters may also allow rainwater to run down the walls of the home, exposing the bricks to high levels of moisture.
Once the moisture enters the brick, it may cause the brick to expand and contract due to natural freeze-and-thaw cycles throughout the year. This expansion and contraction puts pressure on the brick that leads to cracks and splitting. Unwanted moisture may also pass through the brick and enter the home's wooden framing structure, leading to rot and mildew. This type of unseen water damage shortens the life of the structure and can contribute to unhealthy mold within the walls of the home.
Installers apply brick sealant using basic painting techniques. The brick coating typically comes with a clear finish, which can be brushed or rolled onto the surface of the brick and mortar. A paint sprayer helps to speed up the brick waterproofing process for larger structures.
Some paints and primers contain brick sealant, while others do not. Homeowners who plan to paint brick should apply a brick sealant first and wait for it to dry before painting or priming. It's also helpful to wear a mask or respirator while applying brick sealant, particularly when using a paint sprayer.
Existing brick surfaces must be cleaned and prepped before brick sealant can be applied successfully. Dirt and grime can be removed by pressure or power washing. Bleach may be required to eliminate mold or mildew, and to keep it from growing back once the sealant has been applied. White streaks of calcium or salt on the brick, known as efflorescence, can be removed by hand scrubbing or using a pressure washer.