Brick Water Repellents
DEAR TIM: I have a problem with my brick veneer house. It develops leaks during wind driven rains. I can't seem to locate the source of the leaks. I purchased a brick sealer to solve my problem. I saw water repellents at the store, but the salesperson said they don't work as well. What do you think? B. N.
DEAR B. N.: Slow down! Do you still have the receipt for the sealer? You may need it. The sealer you purchased may actually harm your brick house. A water repellent may be a better choice.
The leaks you are experiencing are normal. Brick walls are by no means waterproof. Unfortunately, many homeowners think just the opposite. Bricks and mortar have a great capacity to absorb water. Both contain tiny passageways that actually suck water into the wall. Water can also enter through tiny cracks between the bricks and mortar.
Water leakage into older homes is rarely noticeable. These houses often were constructed using two or three layers of brick or block behind the face brick. As such, they can often absorb all of the rain water until such time as a storm passes. When the sun appears after the storm, the water is released back into the atmosphere through the tiny passageways. In your case, you only have one layer of brick. Once this layer has been breached, the water finds its way into your house.
Look again for cracks or small holes in the mortar. Pay particular attention to the small vertical (head) joints between each brick. This is the most likely place where water is entering. Rarely are these joints filled solid with mortar. The horizontal joints (bed) in your brick wall are usually filled solid and resist water penetration. If you find small holes or cracks, repair these before applying any coating.
There are two categories of clear brick coatings: film forming sealants and penetrating water repellents. Film forming sealants create a continuous barrier on the surface of the brick and mortar. They block the tiny passageways in the brick and mortar. Not only will they stop water from getting into the brick, but they also stop water from getting out. These compounds frequently contain acrylics, mineral waxes (paraffin), urethanes, and silicone resins.
Water repellents work in a different way. These products are designed to penetrate deeply into the brick and mortar. Some can reach as far as 3/8 inch into the surface. They coat the insides of the tiny passageways in the brick and mortar. However, the passageways remain open allowing the brick and mortar to breathe. These water repellents often contain silanes, siloxanes, or a blend of these chemicals.
Film forming sealants can cloud and haze over. They can contribute to brick spalling (flaking) in colder climates. Water repellents rarely discolor brick. Because they soak into the brick and mortar, sunlight has a tough time breaking them down. Check the label on your product to see what chemicals it contains. If it is a film forming sealant, think long and hard before applying it to your brick.