Applying Elastomeric Coatings? Here’s What Contractors Need to Know
Who knew the coating industry was so complicated?
At DFW Urethane, we have been installing several types of coatings since 1981. Even now, there are so many hybrid coating systems on the market that it’s hard to keep track of them all.
These coatings all have their strong points when it comes to construction, so it takes an expert to choose the right one. It takes almost an entire career to become a coatings expert!
Contractors often are only approved to install one type (acrylic, silicone, urethane) of elastomeric coating and approved by only one manufacturer with their chemistry, but that doesn’t mean it’s the best coating for your roof’s needs — every building and part of the country has unique aspects that you have to consider.
For example, if you have a building that gets lots of sun during the summer, you might use a different coating than if your building gets more shade.
There are other things to consider as well. For example, how much pressure is needed to make it spray correctly?
A contractor may only have 200 feet of hose on his coating pump, but what if a customer has a very large roof that will require 500 feet?
For many contractors, this becomes more than they can handle, and they need someone with many years of experience like DFW Urethane to teach them how to do it properly. Very few people in the coating industry have the knowledge necessary to advise a contractor on how to make their product and their equipment spray correctly at 500 feet.
If you’re in the coatings industry, you can only learn by experience because most manufacturers can’t give you field advice either — they’ve never actually sprayed the coating on a roof. In most cases, they just test it in a spray booth using a 50-foot hose at 75 degrees Fahrenheit with no wind. This is very different compared to actual working conditions!
Spraying Acrylic Coatings — What to Consider
At DFW Urethane, we use a lot of acrylic elastomeric coatings in the summer months. It’s a relatively easy product to work with if you follow the manufacturer’s installation and storage instructions. Acrylic is a single-component, water-based product that shouldn’t be left out in freezing temperatures.
It should be stored in a climate-controlled environment, but one of the big problems is that, many times, the material has frozen during transit before the contractor even has a chance to open it.
Most contractors are under the impression that this is the easiest type of coating to apply. However, we know from seeing the problems other contractors have had that application in weather under 50 degrees Fahrenheit and falling or when rain is intermittent can result in coating failure.
Another issue is a wash-off, which happens if it rains before the acrylic coating has had sufficient time to dry.
The most challenging part is knowing when to stop spraying for the day, but even trying to figure out what time of day is best to START spraying can be difficult without lots of experience.
Early in the morning, in our area, roofs tend to have dew on the surface. For proper installation, you need to let this moisture dry before you begin the coating process.
The acrylics will stop curing at about 50 degrees Fahrenheit. If you spray late in the day, and there’s no dew overnight, then there’s a good chance the coating may not wash off and will start curing as the temperature rises above 50 degrees the next day. This is the best-case scenario.
The worst-case scenario would be when you finish coating around 4 pm with the temperature around 55 degrees Fahrenheit — except by 6 pm it’s 48 degrees, and then by 2 am it’s 28 degrees, resulting in the coating freezing; the surface will have hundreds of star-shaped cracks.
This is a serious problem as samples will need to be taken and sent back to the coating manufacturer, not to mention the fact that your hoses might be damaged if you didn’t flush all the material out at the end of the workday. Materials left outside are also at risk of freezing.
Acrylic also has some limitations regarding how thick it can be applied. If you’re not careful, you end up with a situation called “mud cracking,” which is where the surface of the coating cures and shrinks faster than the rest of the coating underneath. It then cracks, making it worthless. These areas should be removed and recoated, requiring additional labor and material costs.
However, some of the newer acrylics on the market can be installed at full thickness in one application, so it’s critical that you understand what kind of coating you’re working with and follow the manufacturer’s recommended application rates.
DFW Urethane recommends developing a deep understanding of the limits of your material, so calling your manufacturer and confirming its limits is a great idea. Many of our manufacturers have winter training schools that only last a few days and are well worth the trip.
Aliphatic Urethane Coatings
Aliphatic urethane coating is a high-performing, color-stable elastomeric coating material that is available in either two components or as a single-component moisture-cured coating, which is one of our favorites at DFW Urethane because of its resilience.
If you live in the Hail Belt, this should be your go-to coating. DFW Urethane has a great deal of hail testing data available. The cost is typically twice that of acrylic coatings.
DFW Urethane used this material in 2016 when the historic Lipscomb Elementary School in Dallas needed a new roof.
This product is very strong and is highly recommended, especially for roofs with heavy foot traffic and lots of mechanical features. However, it does require thinning and should be flushed out of your hoses daily.
Aliphatic urethane coatings are temperature sensitive due to their high velocity. The drums need to be stored in a temperature-controlled environment. The material needs to be above 75 degrees to spray correctly. You also need to use a transfer pump when spraying.
This product has an odor, so be careful when you use it; make sure the fresh air vents are covered and workers wear personal protective gear. We have been using this material since 1990 and have had great results.
Silicone Coatings
Silicone coatings are a very popular material these days, and many manufacturers have a highly solid material to sell you. Here at DFW Urethane, silicone represents about 25% of the coating we install yearly.
It’s a very impressive material that does very well in ponding areas, and its resistance to UV rays are unmatched.
The downside is Silicone’s weakness: it’s not designed to withstand heavy foot traffic and is no match for the large, wind-driven hail in the Hail Belt. Granules installed in the wet topcoat are an excellent idea to add if you plan to put silicone coatings over urethane foam.
Silicone coatings do well in cold temperatures and cure quickly; rain after application is normally not a problem.
Other Coatings to Be Aware of
There are several other coatings on the market that are extremely strong and worth considering, including polyurea. However, in most cases, they need to be top-coated with a silicone. This protects the polyurea from UV rays.
We use polyurea for all of our below-grade waterproofing projects — DFW Urethane has never used polyurea on any of our roofs. However, we are evaluating this product carefully and may try it on roofs someday as more data trickles in.
There are so many other types of materials out there that we just don’t have time to go over, including epoxy, which we use on floors. Some contractors are putting it on roofs, but we have not investigated the viability of this just yet as we’re waiting to see if roofs with epoxy will last longer than 10 years.
If you have any questions or need installation of roof coatings, feel free to contact us — we can’t wait to hear from you!