Every contractor knows there’s more to a major wall coating project than simply applying the coating and walking away.
But with spring around the corner and the lead-up to the busy summer season gaining steam, it’s a good time to review the fundamentals.
1. Know your substrate and coverage rates prior to installation
The big thing to consider here is compatibility. Before starting a project, understand what's already there — whether it's an elastomeric or silicone-based coating.
“While each project is unique, as a general rule, if you have an elastomeric coating on your structure, you want to select an elastomeric because of the movement capabilities. As the building heats up and cools down, the flexible coatings will move at similar rates, avoiding the potential for cracking,” says Dave Fuller, Technical Services Lead at BASF in Shakopee, MN.
Conversely, the only thing that's going to bond or stick to silicone is silicone, so it’s crucial to be certain of the existing coating before you start.
There are a couple tricks to identify if a coating is an elastomeric. Take note of the way the nap laid on the wall or if the coating overtop of sealant or caulking hasn’t cracked. That’s a sign of the flexibility inherent in an elastomeric coating. "When in doubt," says Fuller, "take a sample and have a lab check it out."
2. Weather plays a critical role in proper coalescence
Fuller cautions to never apply wall coatings when surface temperatures are less than five degrees of the dew point (The dew Point can be calculated by using the air temperature and the relative humidity, or through most weather applications. The dew point chart in this handy Wall Coatings Troubleshooting Guide, is available for download).
The dew point refers to the temperature at which below water droplets begin to condense on a surface. Applying a coating at this point risks poor coalescence, adhesion issues or runoff, where the moisture actually carries some of the fresh coating down the wall. Some key considerations include:
- Most products should be applied at a minimum surface and ambient temperature of 40°F (4°C). The temperature should not fall below this for 24 hours after application to ensure proper curing.
- Do not apply if rain is expected within 24 hours. Some low-temperature products can be applied as low as 25°F (-4°C). Be sure to check the coating’s technical data before applying.
3. Consider hydrophobic coatings to significantly reduce dirt
This dirt-resistant technology helps reduce the need for pressure washing, keeping maintenance costs in check. "Hydrophobics are an innovative technology with a specific chemistry that repels dirt and water, which results in a greater defense against the elements," says Fuller. MasterProtect C350 takes approximately 30 days of exposure to sunlight to complete the surface phenomenon, after which dirt and water won’t stay on the surface (watch this video for more information).
4. Texture impacts color
Understand your application methods prior to applying your coating. Using medium or coarse texture coatings can be an effective method to hide different surface imperfections in the substrate. It's always best practice to backroll a coating in the same direction to get a uniform finish. “Textured coatings are like mowing your lawn,” says Fuller.
“If you run your lawnmower one direction, and then run it the other direction, you're going to have two different shades of green due to the different directions the grass is rolled.” It's the same thing when applying textured coatings, he says. “If you roll it up in one stroke and pull it in another, depending on the sun’s angle, the color can appear lighter or darker based on the direction of back-rolling.”
5. Always apply a mock-up to establish color, coverage rates and adhesion
They key here is to test several locations on the building. Color is not necessarily going to appear the same on every side, even if it’s out of the same pail.
“I always recommend replicating as many situations as you can, and always perform an adhesion test,” says Fuller, adding that the ASTM D33-59 Standard Test Methods for Measuring Adhesion by Tape--Test Method A, the X-cut method, is the standard.
Looking for more tips or for someone to help you apply these techniques to a specific job? Contact your local BASF for a job-specific recommendation.