Brick Water Repellents
Brick Water Repellent TIPS
- All brick leaks water
- Old brick buildings have soft inner brick
- Brick veneer is death on a stick
- Silane / siloxane water repellent best
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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.
Brick Walls Have Always Leaked
The leaks you're experiencing are normal. Brick walls are by no means waterproof.
Unfortunately, many homeowners think brick walls are waterproof . 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.
You can build a brick wall that does not transfer water to the inside of a home. The way to do this was discovered hundreds of years ago.
Old Builders' & Masons' Secrets
Water leakage into older homes is rarely noticeable. I'm talking about old brick buildings built before 1900.
These houses and commercial buildings often were constructed using two or three layers of brick or block behind the face brick you'd see on the outside of the wall. The brick in each layer was different
The outer brick that was exposed to the weather was fired longer and hotter in the brick kiln. This created a hard brick that had a low water absorption rate.
The inner, hidden, courses of brick in the wall were softer. They were not left in the kiln as long and were not as hard. They soaked up water like a sponge.
When it storms and wind blows rain against the brick wall the water drops are driven into the wall by the weight of the water and the wind pressure. Usually the water passes where the vertical mortar touches the brick.
The soft brick could absorb lots of water.
When the sun appears after the storm, the water is released back into the atmosphere the same way it came into the brick. The breeze and sun pull the water out of the brick like a tow truck pulls a car out of a ditch.
Brick Veneer - King of Leaks
In your case, you only have one layer of brick. Once this layer has been breached, the water finds its way into your house.
If you could look behind a brick wall that's being lashed by a wind-driven rainstorm, you'd see water flowing down the backside of the wall. It's one of the downsides to having only one layer of brick.
Inspect for Cracks
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.
The method most modern bricklayers use to butter the one edge of a brick is to cut off the mortar from the bed joint of the brick they just laid and use this to butter the end of the same brick.
This does not fill the vertical joint completely and the bond between the mortar and brick is very narrow because the moisture has already been sucked from the mortar after it was cut off the bed joint.
IMPORTANT TIP: Rarely are these vertical joints filled solid with mortar. When the bricklayer spreads mortar over the tops of the course of brick to lay the next course the mortar often bridges the vertical head joint below. There's no guarantee the joint fills 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 past the surface of the brick.
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 repellent contain silanes, siloxanes, or a blend of these chemicals.
You want a silane-siloxane water repellent that's soaks into the brick and mortar. CLICK HERE to get a great one.
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's a film-forming sealant, think long and hard before applying it to your brick.
IMPORTANT INSTALLATION TIPS: When you go to apply a silane-siloxane water repellent you'll want a helper and a backpack leaf blower.
Read the label on the water repellent as they often say once they cure you can't put on a second coat. Some can cure in as little as 15 or 20 minutes.
Many of the products recommend two coats of repellent so you can't get too far ahead of yourself. If the first coat dries, or cures, it will not allow the second coat to penetrate into the mortar joint.
You use the backpack leaf blower to simulate what a fierce storm does. The wind pressure forces rain into the brick. Allow the leaf blower to drive the silane-siloxane water repellent deep into the brick wall. As you spray, your helper blows the repellent into the wall right behind you.