Once you determine a roof coating’s function, you must also consider the type of roof system being coated. Coatings suppliers and manufacturers like Conklin generally offer two types of coatings: all-purpose (suitable for a range of substrates) and application-specific (tailored to one type or a limited range of substrates).
It is important to know that different substrates require different roof coatings. For example, it is more difficult for coatings to adhere to hard, smooth, chemically-inert surfaces and easier on rough, irregular, chemically-active surfaces.
Coating adhesion to a substrate improves when the installer applies a primer or base coat. Manufacturers like Conklin recommend certain primers or base coats to match a specific top coat with a specific substrate. You should use only the base coat or primer specified by the coating manufacturer.
Primers and base coats for built-up roofs offer good examples. Manufacturers have designed products specifically to work on these surfaces - they work well on these often-hot surfaces by bonding to the asphalt and preventing it from bleeding into the white topcoat.
Enhancing a coated roof’s sustainability requires re-coating to extend service life. Most coatings are field-applied, and success depends on real-world conditions and the skill of the installer. To ensure proper curing, an experienced roofing contractor should pay careful attention to consistent application and changing weather conditions.
Please also see the March 2009 facilitiesnet.com article by Reed Hitchcock titled "Different Substrates Require Different Roof Coatings"