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Elastomeric Coatings and Hairline Cracks
Understanding Elastomeric Coatings
Elastomeric coatings are specialized types of liquid applied membranes designed to provide a thick, flexible layer of protection over exterior surfaces. Unlike standard latex paint, which dries into a relatively thin and rigid film, an elastomeric coating maintains a high degree of elasticity. This flexibility allows the coating to stretch and contract alongside the substrate. This characteristic is particularly useful for managing the movement that occurs in building materials due to temperature fluctuations or moisture changes. When applied correctly, these coatings create a seamless barrier that can bridge small gaps and imperfections in a surface.
The primary purpose of an elastomeric coating is to prevent water from penetrating the building envelope. Because these coatings are applied at a much greater thickness than traditional paint, they offer a level of waterproofing that standard coatings cannot match. This makes them a popular choice for masonry, stucco, and concrete surfaces. However, the thickness and the nature of the film introduce specific considerations regarding how the coating interacts with the underlying structure.
The Relationship Between Coatings and Hairline Cracks
Hairline cracks are small, superficial fissures that often appear in stucco, brick, or concrete. These cracks are frequently the result of settling, thermal expansion, or drying shrinkage during the initial curing of the material. While they may appear minor, they can serve as entry points for moisture. If water enters these cracks and then freezes, the expansion of the ice can widen the fissure, leading to more significant structural issues over time.
Elastomeric coatings are often selected specifically to address these hairline cracks. Because the film is elastic, it can bridge the gap of a small crack without breaking. Instead of the coating cracking along with the substrate, the membrane stretches over the opening, maintaining a continuous waterproof seal. This ability to bridge gaps is the defining functional advantage of the product. However, it is important to note that elastomeric coatings are not a cure for structural movement. If a crack is caused by an active foundation shift or a deep structural failure, the coating may eventually stretch to its limit and fail. It is best suited for static, hairline imperfections that do not indicate ongoing movement.
Preparation and Application Requirements
Successful application of an elastomeric coating depends heavily on the preparation of the surface. Because the coating is thick, any debris, loose particles, or previous failing coatings must be removed to ensure proper adhesion. A common first step in preparing an exterior wall is pressure washing. This process removes dirt, mildew, and chalky residues that could prevent the coating from bonding to the substrate. If the surface is not thoroughly cleaned and dried, the elastomeric film may peel or blister shortly after application.
For many surfaces, a primer is a necessary component of the application process. A primer helps to seal the substrate and provides a uniform surface for the thick coating to grip. This is especially important on highly porous materials like stucco or old masonry. Without a proper primer, the substrate might absorb the moisture from the coating too quickly, leading to poor adhesion or uneven thickness. Once the primer is set, the elastomeric coating can be applied through various methods. Spray painting is a common technique for large exterior areas, as it allows for a quick and even distribution of the thick material. However, careful attention must be paid to the application rate to ensure the coating reaches the required thickness specified by the manufacturer.
Thickness and Breathability Concerns
The thickness of an elastomeric coating is one of its greatest strengths and one of its most complex challenges. To achieve the desired waterproofing effect, the coating must be applied much thicker than standard paint. If the coating is applied too thin, it will not have the elasticity required to bridge hairline cracks. If it is applied too thick, it may take an excessive amount of time to dry, or it may crack due to internal stresses during the curing process.
Another critical factor is breathability. All building materials undergo a cycle of absorbing and releasing moisture. In a well designed building, moisture from the interior moves through the walls and evaporates on the exterior. This is often referred to as vapor permeability. Because elastomeric coatings create such a dense and thick barrier, there is a risk that they may trap moisture behind the film. If moisture becomes trapped within the stucco or masonry, it can lead to several problems. The pressure from the trapped water can cause the coating to bubble or delaminate from the wall. In colder climates, this trapped moisture can freeze, causing the coating to crack or even damaging the underlying masonry.
To mitigate these risks, it is important to select coatings that are designed to be breathable. Breathable elastomeric coatings allow water vapor to escape from the substrate while still preventing liquid water from entering. This balance is essential for maintaining the long term integrity of both the coating and the wall system. Homeowners should be aware that applying a non breathable, thick coating over a surface that requires moisture evaporation can lead to significant damage over time.
Safety and Environmental Considerations
When working with heavy duty coatings, it is important to consider the chemical composition of the products. Many modern coatings are formulated to have low levels of volatile organic compounds, commonly known as VOCs. VOCs are chemicals that can evaporate into the air during the drying process. Using products with lower VOC levels is generally better for the air quality around the home and for the health of the person applying the coating. This is particularly relevant when working in confined spaces or during periods of poor ventilation.
In older homes, there is an additional layer of complexity regarding lead paint. If a home was built several decades ago, the existing layers of paint may contain lead. When preparing a surface through sanding or pressure washing, there is a risk of disturbing lead based dust or particles. In such cases, specialized safety protocols must be followed to prevent environmental contamination. It is vital to identify the presence of lead before beginning any heavy preparation work on an older exterior.
When to Use Alternative Methods
While elastomeric coatings are excellent for large surface areas with minor cracks, they are not a universal solution for every repair. There are many instances where other methods are more appropriate. For example, if a crack is wider than a hairline, it usually requires a different approach. Filling the crack with a high quality caulk or a specialized masonry filler is often necessary before any coating is applied. The caulk provides a structural fill that the elastomeric coating can then cover and seal. Applying an elastomeric coating directly over a wide, open crack will likely result in failure.
Other decorative or functional elements of a home require different materials entirely. For instance, an accent wall might be better served by a different texture or color application that does not require the heavy waterproofing of an elastomeric film. Similarly, interior elements like popcorn ceilings or wood stain applications rely on different chemical properties and thicknesses. Elastomeric coatings are strictly an exterior waterproofing tool and should not be used where decorative texture or interior moisture management is the primary goal.
Navigating Rules and Regulations
Homeowners should be aware that applying thick coatings to the exterior of a home can sometimes be subject to local regulations. Some homeowner associations have specific rules regarding the texture and sheen of exterior walls. Because elastomeric coatings can significantly change the appearance of a surface, it is wise to check any existing guidelines before starting a project. Additionally, local building codes may have general requirements regarding how moisture management systems are maintained on a property. While codes vary by location, the general principle is to ensure that the building envelope remains intact and that moisture does not cause damage to the structure or neighboring properties.
Maintaining a home involves a constant balance between protection and breathability. Elastomeric coatings offer a powerful way to seal hairline cracks and protect masonry from the elements. By understanding the importance of surface preparation, the necessity of a primer, and the delicate balance of thickness and breathability, a homeowner can make informed decisions about protecting their property. Proper application and the selection of the right type of coating can extend the life of stucco and concrete surfaces for many years.