Elastomeric coatings were developed in the 1950s to answer the problems of paint cracking and peeling on masonry substrates; concrete, concrete block, cinderblock and stucco. Most substrate materials, particularly masonry, will contract and expand when exposed to heat, weather, moisture in the form of humidity and other climatic conditions. Elastomeric coatings are formulated to handle the expansion and contraction without cracking, often lasting for years longer than regular house paints.
Preparation is the Key to Success
The key to a successful elastomeric coatings project is (to paraphrase the Real Estate industry): preparation, preparation, preparation. The substrate to be coated must be properly prepared to receive the elastomeric coating.
The surface must be cured and have a pH of 9 or less
The surface must be free of any mold-release agents, dirt, grease or other contaminants
Cracks and surface irregularities should be filled with an appropriate caulk or sealant and a surface conditioner (basecoat/block-filler) applied to the entire substrate
Temperature should be between 45 and 100 degrees F
There should be no rain or freezes forecast for 48 hours following the coating
When the conditions are appropriate and the preparation completed, the first coating of the elastomeric may be sprayed or rolled onto the substrate. After a sufficient cure-time, the second coating may be applied. For previously coated surfaces where an elastomeric coating was used, only one coating of a new elastomeric may be required for weather proof protection, but this should be back-rolled to remove any pinholes.
Problems of cracking or peeling of finished coatings projects are most often a problem with the substrate, not the elastomeric coating. The most common cause of peeling is moisture migrating from within the substrate to the surface. The water causes bubbling which breaks and peels. The causes of the water may be from leaks within the building, improperly flashed or sealed eaves or roofing, or inadequately caulked or sealed door and window frames. These should be dealt with by eliminating the source of water penetration and the application of elastomeric caulks.
A high pH is also a common cause of peeling on new masonry surfaces. The alkaline salts migrate to the surface loosening the adhesion of the coating resulting in bubbling and peeling. To check the pH of masonry a “pH pencil” is used. The pH pencil is made from a material that reacts to the alkaline by showing a color range based upon the pH level, when in the presence of water. These pencils may be acquired from a number of sources. The surface to be tested should be clean and dry. Spritz the area to be tested with distilled water, then draw a line with the soft pencil. The pencil line will soon take on a color that represents the pH level and is compared to a color graph to obtain the pH measurement. This test is quite accurate and easy to perform.”
Ask your professional painting contractor if using an elastomeric coating on your home or building will help solve some of these problems.
Article taken from Premiere Painting – Ask the Experts