Armed with a rubber band, as kids, you and a friend may have chased each other engaging in combat. Placing it on your index finger, you draw it back and just as you are ready to fire, snap it breaks. Like a gun jamming, your only weapon of defense has left you vulnerable. The rubber band analogy is one that gives a clear understanding of what elastomeric is and how it performs. Like a rubber band, elastomeric expands and contracts. If broken it becomes vulnerable to failures.
I have been asked many times, can I apply elastomeric on one wall? Or does the entire structure need to be painted with elastomeric? Some customers wanting a quick fix on the exterior to sell a house, or a painter trying to fix a cracked wall within a limited budget. Elastomeric needs a complete seal on a structure to help prevent failures. It is more critical for the heavy build, full blown elastomeric, as open areas can cause an entry point for moisture. The heavy build depends on it’s thick film and elongation to hold itself on the structure. If broken, it lessens its adhesion strength. Think of the bridging capability, it’s not adhering to the substrate where the void of the crack is, but yet it appears to be adhering at the void. The elongation strength is holding it on. Elastomerics quality characteristics can actually work against itself. As the coating expands and contracts, it can actually pull itself off the surface where the coating was compromised. Because the elongation strength can be stronger than the adhesion strength, like of a rubber band when it breaks, the elongation strength contracts it back as it can no longer hold onto itself.
Lets talk about a raw substrate on a structure, meaning a substrate that has never been painted. If you were to paint one wall, or half a wall, there are a few things you should consider. As I talked about in my previous article “Elastomeric Paints” elastomeric shields against moisture on the outside and if moisture were to intrude, then trapping it inside. Having an unsealed substrate next to a substrate where elastomeric has been applied, is like having a widow open during a storm. Unlike the sealed area, moisture will absorb where the substrate is raw, making it an entry point for water to get behind the elastomeric coating. In this picture where the bubble occurred, which was partly due to a foam decorative piece that is not sealed at the top of the structure. This created an entry point for water to intrude, resulting in these bubbles.
Hybrid elastomerics have a greater adhesion strength than their elongation, making it not as dependent on it’s elongation to hold itself on the structure. Unlike the heavy build, it is less likely the hybrid elastomeric will pull itself off if broken. Being the elongation is half of the heavy build and having more adhesion strength. With some exceptions, It is possible to paint a wall without wrapping the entire structure, using a product like Glidden Professional Decra Flex. I would not recommend it on smooth stucco as smooth stuccos pores are tighter and have no texture, giving it less holding power. I would recommend the entire structure be coated with a premium 100% Acrylic product like Sherwin Williams Duration or Vista Paints Duratone. Then apply the hybrid elastomeric to the walls that are desired. It is not recommended to apply any coating over elastomeric other than elastomerics. Other coatings may not have the elongation that the elastomeric has, resulting in the top coat cracking and delaminating.
It is best to consult with a professional paint contractor experienced with elastomerics in your demographic area.