National Coatings Blog

Roof Coatings - Different Classes of Coatings

Posted by Nicole Gale on Thu, Jul 24, 2014 @ 11:34 AM

roof coatingsClasses of Coatings
Roof coatings can be classified into three types:  solvent, water-based, and 100 percent solids.  Solvent systems are those containing an organic solvent as carrier for the coating.  In this case, solvent evaporation causes the coating to form the membrane on the roof.  Water-based coatings employ water as this carrier.  The third class, albeit less common, is the solvent-free coating where two liquid components are premixed in a specially designed airless spray unit; a chemical reaction causes some of these two-part coatings to dry almost immediately.  Each of these three coating classes has specific advantages and disadvantages relating to the type and presence or absence of solvent.

Solvent Coatings
Coatings which employ organic solvents can be applied over a wide range of temperatures, including cold or marginal weather conditions.  Moreover, they will dry quickly under conditions of high humidity since the rate of solvent evaporation is not related to relative humidity.  These advantages are offset to some degree, however, because they contain large percentages of usually flammable, and sometimes highly toxic, organic solvents.

Additionally, many of these coatings are required to carry the D.O.T. classified "red label" associated with low flammability flash point.  This means the applicator must exercise care and prudent handling procedures when transporting, storing, and applying such coatings.  Also, since these systems contain organic solvents which may soften certain asphalt and other conventional roofing materials, they may cause "bleed through" problems or, even worse, permanent damage to the old roofing substrate.  Rooftop air intakes must be masked to prevent vapors from entering the HVAC and ventilation systems.

Finally, when using these materials, additional solvent is required to clean the application equipment after use.

Water-Based Coatings
In contrast, water-based coatings eliminate the flammability and potential toxicity hazards associated with solvent systems since they use water-rather than solvent-as the carrier.  Additionally, the equipment used can be easily cleaned with soap and water, and their potential for "bleed through" is significantly lower because they do not contain solvents.  Since water is an inexpensive solvent, cost is usually lower than solvent-based coatings.

The chief limitation of water-based coatings is the range of atmospheric conditions conducive to application.  First, they should not be applied at temperatures too close to freezing because the rate of water evaporation becomes so slow they may not dry properly.  Normal low cut-off point for application of these coatings is 50 degrees F.  Second, they should not be applied when rain or inclement weather is imminent.

Considerable progress in narrowing this application conditions gap between solvent- and water-based coatings has been made with a recent introduction to the marketplace of systems with "quick set" properties.  National Coatings AcryShield A600 and A640 have this property and can adequately withstand heavy dew or light rain shortly after application.

100 Percent Solids Coatings
The third, less common type of roof coating consists of 100 percent solids.  Since these coatings contain virtually no solvents, they do not possess the limitations of the water- or solvent-based coatings.  However, they do require special application equipment and are extremely sensitive to changes in application temperature as their ability to form a durable, long-lasting membrane is dependent on proper mixing ratios of the two components and reaction temperature.  If incorrect, the coating may not adequately cure or may, possibly, gel prematurely, thus preventing the protective membrane from forming properly.

Acrylic Coatings
Acrylic roof coatings take advantage of the inherent durability of acrylics, and can be designed to be very elastic and flexible over a wide temperature range for a relatively modest cost.  In addition, they are supplied as either water- or solvent-based products, although specialized acrylic coatings are available for roofs experiencing ponded water conditions.

For more information on roof coatings – download our FREE Brochure!
Looking for specific information on restoring a roofing substrate? Download one of our specific brochures:

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Tags: Roof Coating Membranes, Roof Coating Systems, Roof Coating, Single-Ply Roof Coatings, SPF Roof Coatings, Asphalt Coatings, Hypalon Roof Coating, Roof Coatings for EPDM, TPO Roof Coating

AcryShield A502 Roof Coating...Often Imitated, Never Duplicated

Posted by Nicole Gale on Thu, Jun 12, 2014 @ 11:00 AM

roof coatingAcryShield A502 was introduced by National Coatings Corporation in 2006 after three years of intensive research, including both laboratory and actual in-service field testing.  The coating was designed to provide a primer/base coat to be applied to thermoplastic and thermoset single ply membranes, such as PVC, PIB, CPE, TPO and EPDM.  Previously, the only primers used for coating these membranes were solvent borne, which required warning labels, had very high VOC (volatile organic content) and required extreme care when applying to prevent fumes from entering the building.  The only other option for coating EPDM was a "prewash" or "rinseable primer" that had a very high, corrosive  pH, so high that it would react with human skin oils, causing chemical burns. 

AcryShield A502 has three inherent advantages over the previously used primers:

  • It is water borne, so there is no concern about flammable solvents or fumes entering buildings.
  • It replaces both specialty primers for the thermoplastic membranes and the corrosive rinseable primer for EPDM.  Thus there is no need for separate primer/basecoats for different types of roofing membranes.

The next time a project calls for coating single-ply roofing membranes, the roofing contractor, consultant or specifier should demand National Coatings Corporation AcryShield A502

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Tags: Roof Coating Systems, Coating Systems, Coating System, Reflective Coatings for Roofs, Single-Ply Roof Coatings, Coating directly over TPO, Coating directly over EPDM, Hypalon Roof Coating, Coating EPDM, Roof Coatings for EPDM, Environmentally Friendly Roofing System, TPO Roofing, TPO Roof Coating, TPO Roof, TPO Roofing System, Singleply Roof Coating Systems

Adhesion is Important when Applying an Elastomeric Roof Coating System

Posted by Nicole Gale on Tue, Jun 10, 2014 @ 10:00 AM

elastomeric roof coatingAdhesion is the single most important factor when applying a roof coating to your existing roof membrane. Without excellent adhesion, a roof coating system cannot perform as intended and will likely cause leaks and other damage to the roof substrate and building below.

Proper adhesion is obtained by the subsequent factors:

1.    Is the coating compatible with the roofing substrate?

There are multiple elastomeric roof coatings to choose from but they are not all designed to be applied over every roof substrates. There are roof coatings specifically made for Asphalt, BUR, Mod Bit, and Capsheet roofing, there are coatings for Single-Ply Membranes – TPO, EPDM, Hypalon and PVC, and there are coatings intended for SPF, Metal and Concrete roofing substrates. These coatings are all formulated differently to provide the maximum adhesion possible to each of the substrates.

For instance, Single-Ply membranes are the most difficult roofing membrane to adhere to because of how they physically break down and the residue that remains.  Therefore, most roof coatings require a caustic primer or etching rinse to be done before applying an elastomeric coating. This extra step costs money and time but allows for adequate adhesion. National Coatings fortunately has a quick and easy solution for Single-Ply – the AcryShield A502 elastomeric roof coating.  A502 allows for direct and tenacious adhesion to the Single-Ply membrane without the need for a primer or etching rinse.  It is important to find the ideal roof coating that adheres to your particular roof membrane and gives you a cost effective and timely solution for restoring your roof.

2.    How is the surface of the existing roof membrane?

Surface texture provides a rougher area for the coating to grab onto and adhere to. The contact between the coating and substrate can benefit from a slightly rougher surface as the coatings are typically sprayed over the roof and then they spread to fill in the gaps and little dips/pockets in the membrane. This gives the coating a greater surface to adhere to; however, the texture cannot be too harsh as this can also create air pockets between the coating and the roof substrate. It is very important to pressure wash and clean the substrate before any application begins to insure that there is no dirt, film or other residue that could prohibit the coating from directly adhering to the substrate. You also need to make sure there are no areas on the existing roof that are not 100% adhered to the substrate. If so, you need to remove these areas before applying the roof coating as this can also cause air pockets and defects in the roof coating system. 

3.    Cohesion

Lastly, we will discuss cohesion or the coatings properties that produce the strength and bonding ability to hold itself together as a cured and durable coating. Weather conditions, coating thicknesses and cure times are all factors that can either enhance or diminish the cohesion in the coating.  It is necessary and important to follow the manufacturer’s recommended application guidelines as each manufacturer has different requirements for obtaining ideal cohesion.

To learn more about National Coatings elastomeric roof coatings and restoration systems, download our FREE Benefits Brochure.


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Tags: Roof Coating Membranes, Roof Coating Systems, Coating Systems, Coating System, Roof Coating, Elastomeric Roof Coating, Ultra High Reflectance Roof Coating, Commercial Roofing, Roof Coatings for EPDM