1. LIQUID STANDARDS:
A: ASTM D-2196: Viscosity as measured in centipoise (cps) or Krebs (KU). The liquid coating must fall between 12,000 and 85,000 cps or 85 to 100 KU.
B: ASTM D-1644: Weight-Solids percent. This measures the solids left after the film is cured. A minimum of 60% solids is required.
2. CURED FILM TESTS:
A: ASTM D-2370: Initial Tensile Strength measures the toughness of the dried coating. The minimum required is 200 psi.
B: ASTM D-2370: Initial Elongation. Along with part A above, this same test measures the limits for stretching of the cured coating. A minimum of 100% is required.
C: ASTM D-1653: Permeance. This is a measurement of how much resistance the coating has to moisture as well as how much water vapor can escape from underneath. A very high number may indicate that a coating does not have sufficient resistance to moisture. A very low value may indicate that a coating will be unable to allow vapor trapped underneath the roof to escape properly. A maximum of 50 perms is allowed in order to pass.
D: ASTM D-471: Water Swelling. This test shows how much the cured coating will swell or increase when subjected to water. A maximum of 20% is allowed.
E: ASTM C-794: Wet Adhesion measures strength and peeling characteristics of the cured coating. A minimum of 2 lbs per linear inch is required.
F: ASTM D-624: Tear Resistance requires that the cured coating must be able to withstand at least 60 foot pounds per inch of force before beginning to tear.
G: ASTM G-21: Fungi Resistance requires that a cured coating must have a zero growth rating against fungi/mold over a given amount of time in order to pass this test.
3. WEATHERING TESTS FOR CURED FILM:
A: ASTM D-522: Low Temperature Flexibility. After 1000 hours of weathering the cured coating is tested at -15 degrees F. for cracking while being bent over a mandrel. If no cracking is observed the coating passes and is considered flexible at low temperature.
B: ASTM D-2370: Elongation After Weathering measures a coatings elasticity after 1000 hours of weathering. A minimum of 100% elongation at 73.4 degrees F. and 40% at 0 degrees F. is required.
C: ASTM D-4798: In the Accelerated Weathering film test the cured coating is weathered for 1000 hours and checked for evidence of cracking. The coating must have zero evidence to pass.
Together, these ASTM tests comprise the ASTM D-6083 standard for elastomeric roof coatings. This is an all or nothing standard for achieving certification. it is an extremely useful tool for establishing a benchmark for roof coating performance.
One should be wary of claims for a roof coating passing a single or several ASTM tests. This is not the same as having passed the D-6083 standard. This is why the standard exists in the first place. It should be the starting point for evaluating different roof coatings.
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