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Sealing and Resealing Concrete and Masonry

The terms “waterproofer” and “sealer” are often used interchangeably when it comes to concrete and masonry coatings, but they are not the same things. Knowing the difference between the two can help contractors and consumers avoid problems down the road.

Waterproofers are generally made from rubber, plastic or a sealing agent. They’re designed to keep moisture both in and out, penetrating the pores of the masonry and expanding as it dries to become a part of the masonry, creating a continuous film.

A water sealer, however, is a repellent designed to cause water to bead up on a surface while allowing moisture vapor to pass through. Sealers are typically applied in such a way as to permeate the substrate, which is usually very porous, ensuring that the substrate is sufficiently covered. Water sealers can be applied with a brush, roller or sprayer. Only one coat is recommended unless the surface is extremely porous.

The idea that water can wreak havoc on masonry or concrete may sound strange, but constant exposure to water — and especially winter freeze/thaw cycles — can damage or destroy masonry surfaces in a surprisingly short amount of time.

For above-grade brick or masonry surfaces exposed to wind-driven rain or other weather elements but not subjected to hydrostatic pressure (the weight of a body of liquid pressing down on a surface), a water sealer fits the bill nicely. A sealer will satisfactorily protect the surface and maintain its original beauty. Waterproofers, on the other hand, are usually pigmented products that tend to change surface appearance.

Different situations, different sealers
The most common types of sealers are silane, siloxane and silane/siloxane blends and are typically available in waterborne and solvent-borne formulas. Several types of sealers are specifically formulated to help protect against water damage. Colorless sealers for vertical surfaces are available as are sealers designed to leave a sheen, add protection, or provide color. There are also sealers that act as moisture vapor barriers, as water-repellent barriers (such as silicones) and as a finish coat.

Most sealers work by penetrating the pores of the masonry and preventing moisture. However, for a vertical surface, it’s important to ensure that moisture is kept out but that water vapors are able to escape, so you don’t create an environment for mold to grow.

Sealers work much like waterproof fabrics such as Gore-Tex®. While Gore-Tex features a proprietary weave that’s fine enough to block big water droplets such as rain from passing through the fabric, the weave is just loose enough to enable smaller water vapor droplets to escape. Sealers work much in the same way, with slight molecular gaps that are too small for moisture droplets to get in, but large enough for vapor to escape.

A word of caution, though. Because sealers can dry clear with no sheen, consumers sometimes think they haven’t applied enough product. If too much product is applied, the surface can become slippery, blotchy and even darken the color of the masonry surface.

There are many different choices when it comes to deciding which concrete or cement sealer is right for your outdoor sealing project. Durability, cost and appearance will all play a part in the decision you make. If your concrete has ever been sealed in the past, you will also need to consider the new sealer’s compatibility with your existing sealer. We offer a full range of sealer options for all types of driveway, patio, sidewalk and outdoor concrete and masonry sealing projects.