To water seal a brick wall, you can apply exterior coatings designed to prevent water penetration while allowing the wall to breathe.
According to referenced information from October 10, 2023, waterproofing old brick can be achieved by coating the exterior masonry with specific materials:
- Silane or Siloxane Penetrating Sealers: These are chemical sealers that penetrate the pores of the brick and mortar, reacting to create a hydrophobic (water-repelling) layer beneath the surface. They typically do not change the appearance of the brick.
- Vapor Permeable Hydrophobic Paint: This type of paint forms a surface barrier that repels liquid water but allows water vapor from inside the wall to escape. This is important for brick walls to prevent moisture buildup behind the coating.
- Traditional Lime-Based Non-Polymer Modified Stucco with a Vapor Open Hydrophobic Coating: This involves applying a specific type of stucco over the brick. The stucco itself is lime-based (traditional, allowing vapor movement), non-polymer modified, and it is then finished with a hydrophobic coating that repels water while remaining vapor open (allowing moisture vapor to pass through).
Methods for Water Sealing Brick Walls
Selecting the right method depends on factors like the age and condition of the brick, desired appearance, and budget. The key is to choose a treatment that prevents liquid water from entering while allowing water vapor to escape, preserving the integrity of the masonry.
Here are the primary methods based on the reference:
1. Penetrating Sealers
- What they are: Liquid chemicals, often based on silane or siloxane, applied to the brick surface.
- How they work: They soak into the pores of the brick and mortar, bonding chemically to create a water-repellent zone just below the surface.
- Benefits:
- Typically do not alter the look or color of the brick.
- Allow the brick to breathe (vapor permeable).
- Can be effective at repelling rain penetration.
2. Vapor Permeable Hydrophobic Paint
- What it is: A specially formulated paint designed to repel water while still allowing moisture vapor to pass through.
- How it works: Forms a protective, water-repellent film on the surface of the brick. The "vapor permeable" characteristic means that humidity or moisture trapped within the wall can slowly evaporate out through the paint layer.
- Benefits:
- Provides a change in appearance (color).
- Offers a surface barrier against water.
- Maintains vapor permeability, crucial for wall health.
3. Traditional Lime-Based Stucco with Coating
- What it is: A plaster-like material (traditional lime-based, non-polymer modified stucco) applied as a render over the brick, finished with a vapor open hydrophobic coating.
- How it works: The stucco layer provides a protective shell. Using traditional lime stucco (rather than modern cement-based) ensures breathability. The final vapor open hydrophobic coating adds water repellency to the stucco surface while maintaining the ability for moisture vapor to escape from the wall structure through both the stucco and the coating.
- Benefits:
- Offers significant weather protection.
- Can drastically change the appearance of the wall.
- Using lime stucco and a vapor open coating helps manage moisture within the wall system.
Choosing a water sealing method that is vapor permeable or vapor open is generally recommended for brick walls. Brick and mortar can hold or absorb moisture from various sources (e.g., rising damp, condensation, wind-driven rain). If this moisture becomes trapped within the wall by an impermeable coating, it can lead to issues like spalling (surface deterioration), efflorescence (salt deposits), mold growth, and reduced insulation value, especially in colder climates due to freeze-thaw cycles.
