If I had a dollar for every time I was asked this question I would be rich! In the paragraphs below let's explore if your coating has ponding water resistance and better understand the underlying concept.
First, ASTM D6083, the governing specification for acrylic roof coating, has certain minimum LABORATORY requirements related to ponding water. The first is ASTM D1653, "Test Method for Water Vapor Transmission of Organic Coated Films". In this test, a piece of the roof coating is used as the bottom of a cup and the amount of water that passes through this assembly is measured. Lower values indicate that the coating is more water resistant.
(Above: ASTM D1653 Test)
The second test in determining if your coating has ponding water resistance is ASTM D471, "Test Method for Rubber Property Effects of Liquids". Simply restated, this test determines how "sponge-like" the coating is when submerged in water. Lower numbers indicate the coating will be less prone to swelling when submerged. Less swelling reduces stress at the bond between the coating and the roof substrate.
(Above: ASTM D471 Test)
The third test is ASTM C794,"Test Method for Adhesion-In-Peel of Elastomeric Joint Sealants". This test measures dry and wet peel adhesion. The wet peel adhesion test is conducted immediately after the coating and roofing substrate have been submerged in water for one week.
(ASTM C794 Test Assembly Shown Above)
A caveat here: The test does not specify the roof substrate to be tested. If my roof of interest is sprayed foam and the D6083 test data is for galvanized steel, then these results are meaningless.
Now let's return to the "Real World" of ponding water resistance. If I remove my lab coat and put on my consultant/contractor cap and want to determine if a coating has "Ponding Water Resistance", I go on the roof, walk over to an area where water has ponded, press on the coated roof with my thumb and see if the coating is adhered or has delaminated. The slide below shows two sprayed foam mock-ups designed to hold water. After 2 weeks of continuous immersion, the difference is compelling.
The 2'x3' trays have been sprayed with polyurethane foam and top-coated with two different acrylic coatings. The trays are sloped to create areas where the coated mockup is dry and wet. The coating on the left is badly wrinkled, while the coating on the right is completely adhered. The glossy surfaces are ice, as the ponded areas have frozen.
To conclude: the "Real World" question should not be "Does your coating have ponded water resistance?" but rather "Does it stick when it is wet?"
Check out our AcryShield A502 and AcryShild A503 base coats which offer advanced resistance to poned water on your roof and provide maximum adhesion to Built-Up roofing and Single-Ply membranes without the use of sacrificial or caustic primers.
