Hello from your friends at Pro Mason Supply! We often get questions from customers, both seasoned pros and dedicated homeowners, about the best way to protect their beautiful brick and stone structures from the elements. It’s a great question! Proper moisture management is key to the longevity of any masonry work, especially historic buildings.
However, a common misconception is that all protective coatings are created equal. Many people reach for a "sealer," thinking they're locking water out. Unfortunately, with older masonry, they might actually be locking it in, leading to significant damage. Let's explore the crucial difference between traditional sealers and modern water repellents.
The Problem with Film-Forming Sealers
When most people think of sealing their brick or stone, they're picturing a traditional, film-forming sealer. These products, often acrylic or urethane-based, create a solid, non-porous film on the surface of the masonry. It sounds like a good idea in theory—if water can't get in, the wall is protected, right?
The issue is that masonry, especially historic masonry set with lime-based mortars, needs to breathe. This means that water vapor from inside the structure (or moisture absorbed from the ground) must be able to escape through the surface.
When you apply a film-forming sealer, you essentially wrap your building in a plastic bag. While it might block some rain from getting in, it also traps any moisture that is already inside or finds another way in (through cracks, failed flashing, etc.). This trapped moisture is where the trouble begins:
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Spalling and Flaking: In colder climates, trapped water will freeze and expand, causing the face of the brick or stone to pop off or flake away. This is called spalling, and it causes irreversible damage.
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Efflorescence: As trapped water dissolves natural salts within the masonry and then evaporates, it leaves behind ugly white, powdery deposits on the surface called efflorescence. A film-forming sealer can trap these salts behind the film, causing them to build up and push the sealer off the wall.
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Accelerated Mortar Decay: Mortar joints are designed to be the "release valve" for moisture. When the entire wall is sealed, the mortar remains saturated for longer periods, leading to rapid deterioration and decay.
For these reasons, we almost never recommend a film-forming sealer for historic or traditional masonry. It's often a counterintuitive step that can cause more harm than good.
A Better Way: Penetrating Water Repellents
So, how do we protect vulnerable masonry without trapping moisture? The answer lies in modern, penetrating water repellents that utilize silane/siloxane technology.
Unlike a sealer that sits on the surface, a penetrating water repellent soaks into the pores of the brick and mortar. It then chemically bonds with the substrate to create a hydrophobic (water-repelling) lining within those pores.
The key difference is that this process does not seal the pores. It leaves them open to water vapor, allowing the wall to breathe naturally. Liquid water from rain is repelled due to surface tension—the water beads up and rolls off—but water vapor from inside can still pass right through.
Our Pro Mason Responder Water Repellent is a perfect example of this advanced technology. It provides excellent protection against water intrusion without compromising the essential breathability of your masonry.
When to Use a Water Repellent
While not every masonry wall needs a water repellent, they are incredibly effective for areas that take a constant beating from the weather. Think about parts of your building that are highly exposed and lack protection:
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Chimneys: Often the most exposed part of a building, chimneys are battered by wind and rain from all sides.
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Parapet Walls: Low walls extending above the roofline are highly susceptible to saturation.
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Walls with No Overhang: Any masonry surface that doesn't have the protection of a roof or eaves will absorb more water during a storm.
In these high-exposure situations, an application of a quality water repellent like Pro Mason Responder Water Repellent can drastically reduce weather-related damage and extend the life of your masonry and mortar joints.
Easy to Use, Powerful Protection
One of the best parts about modern water repellents is how user-friendly they are. You don't need complicated or expensive equipment for a successful application. Our Pro Mason Responder Water Repellent is a low-odor, water-based product that is easy and safe to apply.
For most projects, all you need is a simple, low-pressure garden sprayer (like a "pump-up" sprayer). You apply the repellent in a gentle flood coat, starting from the bottom and working your way up, ensuring the surface looks wet for a few minutes. For smaller areas or detail work, a simple brush or roller will also do the trick.
Protecting your masonry project doesn't have to be complicated. By understanding the difference between harmful sealers and breathable water repellents, you can make the right choice to preserve your beautiful brick and stonework for generations to come.
If you have any questions about your specific project, don't hesitate to reach out to us here at Pro Mason Supply. We're always here to help you build and restore with confidence!
