How to Seal Brick and Other Masonry Buildings

December 11, 2012

Water entering a masonry substrate can cause your home to have interior leaks or exterior staining, spalling and efflorescence. Usually the masonry substrate can absorb the liquid water and release it again when it stops raining. However, the masonry could still have staining and efflorescence.

In modern home construction, masonry is used as a veneer. That is, homes and buildings that have brick, stone, stucco or some other masonry exterior are traditional wood or steel buildings on the inside. The veneer is just a cosmetic look. Therefore, improper building practices can cause leaks into the house or around windows and doors. At the more extreme circumstance, improper building practices can cause the structure of the building to become damaged due to water.


Efflorescence is the whitish staining that is seen on the surface of brick and masonry. This is actually the accumulation of salts from the brick itself. What happens is that the water inside of the brick dissolves the natural salts that are present from the manufacturing of the brick. Then the water evaporates to the surrounding air, leaving the salts on the surface to be seen.


Spalling is when the brick or masonry substrate flakes. This can be caused by water freezing inside of the brick and expanding. The expansion causes the brick to break and flake.

Now, to waterproof brick or masonry it must be sealed against water penetration. But be careful. A surface sealer such as acrylics, silicones or epoxies can actually trap water vapor from the inside of the building from getting out. As mentioned before, this can cause spalling.

Brick pavers and concrete sidewalks or driveways come under attack from deicing salts. These salts do extensive damage to the substrate. By sealing the surface, the salts will not be able to do damage to the substrates.

The best way to waterproof and seal a brick or other masonry substrate is with a penetrating siloxane based sealer. The siloxane actually penetrates into the masonry substrate and chemically bonds to it. This fills the pores and prevents liquid water from penetrating. However, siloxanes are 100% breathable. So water vapor from the interior can still escape from the brick. This will reduce spalling.

Siloxanes have the added benefit of not coloring or darkening the substrate. They are clear and do not leave a glossy sheen. Since siloxanes penetrate the masonry and are not on the surface, the original texture of the surface is maintained. And the penetration into the masonry substrate actually protects them from the elements. They will be long lived and give years of maintenance free performance.


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