How liquid-applied systems work and what to look for
Roof construction details generally specify tough, thick materials or use reinforcement to spread stress away from the point of movement over a broader area. In these areas, the critical characteristic of crack-bridging is primarily a function of tear strength, more so than the more commonly reported physical properties of tensile strength or elongation. Tear is a test of strength when there is a flaw or irregularity, and this is always the case in actual roofing practice.
In addition to considering tear strength, in order to function properly, detail design must allow for adequate low-temperature flexibility (LTF). If the material hardens severely as temperatures drop, it will no longer spread the stresses at the detail. When reinforced, a cold or stiff material will cause the fabric to shear, because the fibers can no longer move as intended in the composite. Details are stressed the most when materials contract due to cold temperatures, making low-temperature flexibility a key benchmark when comparing liquid-applied systems.
Conclusion
The overall condition and performance expectations of an existing roof provide the basis for what level of protection is needed. Only occasionally can that be satisfied with paint or a thin coating. Much of the time, the roof will need some repairs while the field of the roof is still functional, and can be improved by a coating application. More severely leaking and deteriorated roofs often indicate the need for a membrane system, as well as for extra impact resistance or a longer service life beyond what a coating can provide.
Repairs and retrofit solutions utilizing liquid-applied approaches are available for almost all forms of commercial roofing. These liquid-applied systems are not simple paint jobs, but are roofing installations done by experienced roofing professionals. Not every roof is a good candidate, due to either economic considerations or material properties limitations as a result of age. For most roofs, there a point in the life cycle when a liquid-applied solution is a good option. Given the right materials and methods, most roofs can remain in service longer with the help of liquid-applied roofing products.
Steven Heinje is the technical manager of liquid-applied systems for GAF. He has degrees in biology and chemistry, along with an MBA. Heinje has 30 years of experience in roof coatings, specializing in acrylic elastomers and urethane coatings. He is a vice president and board member of the Roof Coatings Manufacturers Association (RCMA), and leads several task groups in ASTM D08 roofing, as well as maintaining active memberships with American Society for Quality (ASQ), RCI, Reflective Roof Coatings Institute (RRCI), and the American Chemical Society (ACS). Heinje can be reached at sheinje@gaf.com.
