What are Elastomeric Coatings?
Elastomeric coatings are fluid-applied roofing membranes with elastic properties that allow it to expand and contract with the substrate.
Elongation in roof coatings typically ranges from 300 - 800%. Without good elongation, a roof coating is no longer considered an elastomeric.
As the membrane thickness goes up, elongation increases while tensile strength decreases. Elongation is important because roofs tend to expand and contract to allow the coating to move with the substrate and not crack or peel off.
ASTM D6083 requires a dry film thickness of 20 dry mils for testing.
Tip: Studies have shown that roof coatings applied at 30 dry mils provided the best performance and longevity. 30 dry mils is approximately the thickness of a credit card.
Oftentimes, contractors will sell a 2 coat system but fail to specify the total dry film thickness of the installed membrane. If in doubt, please ask us for details and clarification. They should strive to put down at least 30 dry mils to ensure they are getting at least 25 dry mils on any thin areas.
Types of Elastomeric Coatings
Water-based, acrylic elastomeric roof coatings are widely used over metal roofs and spray foam roofs by contractors and building owners performing a DIY restoration. They are best used on roofs that don't pond water.
Solvent-based elastomeric coatings have higher ponding water resistance and is more suitable for low slope or flat roofs. Solvent-based roof coatings have much better ponding water resistance than acrylic roof coatings.