How to choose the best elastomeric roof coating

May 16, 2017

An elastomeric roof coating is a coating applied to a variety of roof types to protect the underlying roofing material, help stop and prevent leaks, and limit future weathering.  Some also cool the building. The coating stretches and moves, giving it an elastic quality. Elastomeric roof coatings can be used on many industrial and commercial roof types such as metal roofs, concrete roofs, bitumen, modified bitumen or BUR roofs, EPDM roofs, or as a sealant over new PUF roofs.

The best value from a roof coating comes when you apply it at the first sign of aging. By making needed repairs early, installing a full protective barrier at the same time, you create your “stitch in time that saves nine.” Wait too long and it is likely to cost you more. Too often, it costs you a new roof, at three or four times the expense of a roof coating, which could have been avoided by paying attention to early signals.

After reviewing all of the many elastomeric roof coatings on the market, how do you select the best quality and value roof coating for your needs?

Physical Properties to Consider in Elastomeric Roof Coating Purchases

When determining the best elastomeric roof coating to use on your roof, there are many physical properties that need to be taken into consideration. Every roof is different in terms of construction, location, weather, sunlight, etc. It is impossible to ever know which physical characteristic will prove most important to the durability of your roof system, so we highly recommend you compare every one of them when you are reviewing the available roof coating products. The best roof coatings should perform well for you on every count.

Here are the properties to evaluate:

  • Elasticity/Elongation: Elasticity is the ability of a material to stretch and recover. The ability to stretch and recover means that a roof coating can move with the expansion and contraction of the roof as the temperature changes without cracking. The better the elasticity, the more likely the product will endure.
  • Tensile Strength (new): Tensile strength measures the ability of the product to hold together and avoid breaking. Roof coating companies typically report tensile strength when the product is new and in the lab.
  • Tensile Strength (aged): The tensile strength of a roof coating can deteriorate rapidly over time with exposure to the weather. We highly recommend that you select a manufacturer that can provide you with written, third-party tensile strength measurements of their coatings when they are aged and have been exposed to the elements. It provides you an added level of comparison. The aged measurements of the best roof coatings often beat the competitors’ new product measurements. That signifies a serious difference in coating quality and value over time.
  • Perm Factor: The perm factor is the coating’s resistance to moisture passing through it. A lower number shows greater moisture resistance. Lower is better, as moisture is the enemy of any roof.
  • Moisture Gain by Weight: Moisture gain by weight is the ability to absorb water vs repel water and protect the roof beneath. You want a roof coating that repels water away from the roof, rather than absorbing into the roofing material which can accelerate aging and deterioration of the roof itself.
  • Peel Adhesion: Peel adhesion measures the ability of the coating system to remain adhered to the roof surface under adverse conditions. If your roof coating doesn’t stay firmly attached, then it can’t properly protect your roof.
  • Tear Resistance: The tear resistance of a coating is, just as it sounds, the resistance to tearing which can happen due to foot traffic, from roof movement, or from other shifts in the environment.
  • Reflectivity: Reflectivity measures how much heat and light is reflected away from the roof by the coating. A cool, reflective roof surface allows all building components to work more efficiently and reduces maintenance needs and premature roof failure caused by UV damage and thermal shock.

Roof Coating Standards Provide a Necessary Point of Reference

The American Society for Testing Materials (ASTM) supplies national standards for testing procedures of elastomeric roof coatings. This allows purchasers to have a reliable set of standards when evaluating the best elastomeric roof coating for a roof. This is an excellent starting point for asking questions of what you want used for your project.

The ASTM includes testing standards for elasticity, tensile strength, perm factor, moisture gain by weight, peel adhesion, and tear resistance. They stress that ALL of these characteristics hold equal importance when evaluating a roof coating, having good results on just one element is not enough to use for selection criteria.

Selecting the best roof coating can have serious long-term implications, so at Topps, we actually recommend that you take your questions a few steps further than simply the ASTM standards, and focus on the entire package. You can risk everything by not choosing the right feature to focus on.

Consider real physical properties over fancy advertising copy. Only one will provide you with maximum benefits. Make certain that the product you choose is the most desirable option for your climate. Selecting a coating that can withstand any climate, likely has applicability to you. Climates often involve various extremes during different seasons. Physical properties aside, your conditions may be quite different from others in more respects that matter.

Third-party independent testing, beyond those used only for marketing purposes, can be valuable without costing you more.

Because Miami-Dade County Florida has what most consider the gold standard set of requirements for roof coating characteristics, where passage is required for legal use in those areas, it can be an excellent starting criteria. Miami Dade has an incredibly complex set of potential weather conditions (think heat, high humidity, hurricanes, etc.) and thus, needs very high standards for performance in building materials.

In addition to having requirements for performance when new in the lab, they also require roof coatings to be tested when they are aged. After a coating is aged, you can get a much better understanding of the rate at which it ages and deteriorates. This will tell you much more about its value than initial lab testing on a new product. Their reporting shows you how it compares.

Ask your vendor about the use of their products across various conditions, but also Miami Dade standards. Are they approved for Miami Dade county? Can they provide you with the results of tests conducted on their aged products after exposure to the weather? This information is critical to finding the very best roof coating product available. Your location may not be exactly the same, but its likely it can involve a variety of conditions including these.

Last, but not least, the ability of your roof coating to provide a cool roof is incredibly important. UV rays and thermal shock can cause serious damage and deterioration to a roof. A white elastomeric roof coating, having proven solar effective properties, provides protection against heat and therefore can also help to dramatically reduce energy required to cool your building. We recommend seeking out products that hold the ENERGY STAR® recognition to ensure that the roof coating product you are purchasing is providing you with these important cooling benefits.

Again, this is one component among a number that can be valuable to you. So consider the entire package. If your white roof coating degrades quickly over time it can lose the energy and cooling benefits it initially offered. Consider those instead who also use CRRC for third-party verification on cool roof considerations over time if this is important to you. Here again, coatings which diminish more quickly in cooling qualities typically are shorter in value in the other important physical factors above. You don’t want it to be the weak link in your “value chain”.

Selecting an elastomeric roof coating is an important decision that can have a significant impact on the longevity of your roofing project and on the roof itself. Be sure when you select a product that you ask questions about all of the physical characteristics of the product and how it is rated by third-parties like ASTM and CRRC.

Go in wise. Know that comparing literature reports of a product new and in the lab are good as a starting point.  Be sure to dig deeper to ensure the that you select the best roof coating for all of your needs. The coatings that perform better on more areas are more likely to meet your needs over time.

Have questions? Feel free to contact Topps for information on roof coating standards and how our products stack up.

Reduce Your Energy Bill with Elastomeric Roof Coatings

Reduce Your Energy Bill with Elastomeric Roof Coatings

Topps white roof coatings reflect the sun and keep your roof much cooler. See how our client saved over 24% on their AC bill.

See Case Study