Paint does more than change the appearance of a building. In some cases, it can contribute to long-term damage, especially when applied to masonry surfaces. While paint might seem like a simple finishing touch, the type of coating used on a brick or stone facade can have serious consequences for the building’s integrity.
One of the common but avoidable issues seen in the field involves coatings that do not allow moisture vapor to pass through effectively. These coatings can trap moisture, prevent proper drying, and accelerate deterioration beneath the surface. However, not all coatings are equally impermeable.
Keep reading to understand why breathability matters, how improper coatings can lead to damage, and what property owners and facility managers should consider when maintaining or restoring masonry facades.
What Is Non-Breathable Paint?
Masonry materials like brick, block, and stone are porous. They naturally absorb and release moisture through vapor diffusion. This breathability is essential for the long-term performance of the wall system, especially in climates with freeze-thaw cycles.
Non-breathable paint refers to coatings that restrict moisture vapor transmission. However, not all acrylic, elastomeric, or solvent-based coatings are inherently non-breathable. Perm ratings, measured using ASTM Standards such as D1653 and E96, indicate a coating’s ability to allow water vapor to pass through. Higher perm ratings indicate greater breathability, while lower perm ratings indicate less permeability.
For example, some acrylic and elastomeric products have tested perm ratings that allow for moisture vapor transmission, reducing the risk of trapped moisture and subsequent damage. Always refer to a product’s technical data sheet to verify its perm rating before application.
7 Symptoms of Paint-Related Masonry Damage
Non-breathable coatings can trap moisture inside masonry walls, leading to potential damage beneath the surface. However, it is important to note that moisture-related issues can also result from failing caulk joints, poorly sealed roof caps, or other building envelope failures. Here are the common signs we see in the field:
1. Surface Cracking or Bubbling in the Paint Layer
Trapped moisture behind the coating may cause blistering, bubbling, or visible cracks. However, these symptoms can also indicate issues such as deteriorating caulk joints or poorly sealed roof caps. Identifying the source of moisture is key to resolving the underlying problem.
2. Chunks of Paint and Surface Material Detaching
As pressure increases, large areas of paint and sometimes outer layers of masonry may peel or shear off. This indicates significant stress behind the surface and may require further investigation to determine the moisture source.
3. Brick or CMU Displacement from Internal Moisture Expansion
Excess moisture trapped within the masonry can expand and shift bricks or blocks out of alignment. This is particularly common in CMU or composite wall systems.
4. Bowing or Bulging Walls
When internal pressure has nowhere to go, it can force wall sections outward. This is a serious structural issue and may require partial or full reconstruction.
5. Facade Cracks and Shifting Joint Lines
As the wall system moves under pressure, cracks may develop along mortar joints or within the masonry itself. Monitoring these areas can help identify potential structural issues before they escalate.
6. Interior Water Intrusion
If moisture cannot escape through the exterior, it may travel inward, resulting in stained drywall, damp insulation, or visible water leaks. However, improper application, caulk failure, or high moisture content prior to painting may also contribute to this issue.
7. Localized Material Failure
Eventually, weak points give way. This can include small wall collapses, partial veneer detachment, or complete failure of individual masonry sections under pressure.
In some cases, the paint layer may appear intact for years before signs of deterioration emerge. The early signs can be subtle, but once underlying issues begin to accelerate, the repair process often becomes more complex and costly.
Appropriate Coatings and Treatments for Masonry
If a coating is required for aesthetic or protective reasons, it is crucial to verify its perm rating and ensure that it meets the required breathability standards for masonry. Common breathable products include:
- Mineral silicate paints
- Limewash or lime-based coatings
- Specialized masonry stains or breathable sealants
Before applying any coating, confirm that the moisture content of the masonry is within acceptable limits. According to AIA Masterspec, the maximum allowable moisture content for concrete, CMU, and masonry surfaces is typically 12% or below. Moisture levels should be measured using an electronic moisture meter prior to application.
When to Call a Professional
Identifying and correcting coating-related damage often requires a comprehensive evaluation of the wall system. This includes assessing the perm rating of existing coatings, inspecting caulk joints, roof caps, and other potential moisture entry points, and measuring moisture content prior to any repair or repainting.
A qualified contractor will also understand how to safely remove coatings without damaging underlying brick, block, or stone and will be able to recommend breathable alternatives when recoating is necessary.
About Building Restoration Corporation
With over 40 years of experience in exterior building repair and restoration, Building Restoration Corporation specializes in historic preservation and masonry restoration including sensitive coating removal, tuckpointing, and facade stabilization.
While we are not a commercial paint contractor, we are a team of skilled professionals who understand the materials we work with and how to preserve them for the long term. From historic buildings to modern commercial properties, we approach every project with a focus on durability, safety, and detail.
Schedule an Evaluation
If your building has been painted and you are noticing signs of deterioration, or if you are planning a restoration project and need expert input or a building evaluation, our team can help.
📞 Call us at (612) 789-2800
📧 Email: info@buildingrestoration.com