Understanding the Concept of Ponding Water
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.
The second test 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.
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.
Now let's return to the "Real World" of ponding water resistance. If we remove our lab coats and put on our consultant/contractor cap and want to determine if a coating has "Ponding Water Resistance", we would go on the roof, walk over to an area where water has ponded, press on the coated roof with our thumb and see if the coating is adhered or if it has delaminated. A good roof coating with superior protection against ponded water would look no different under water as it does above water. The adhesion would be the same and there would be no peeling or delamination occurring. (Check out NCC’s base coats, which provide excellent waterproofing, superior adhesion, and resistance to ponded water!)
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?"
Call National Coatings 800-423-9557 or go to our Contact Us page if you have questions or concerns regarding ponded water. We are here to help you!