What is the difference between GALVALUME roof systems that use concealed and exposed fasteners?
There are several variations of concealed fastener systems. For low slope structural systems, panels are overlapped and lockformed or snapped together at the seams and held down with clips, one end of which is overlapped in the seam and the other end fastened to the structural member of the roof. The clips have a sliding feature that permits the roof panels to “float” during expansion and contraction from ambient temperature changes.
Exposed fastener systems use fasteners that are driven through the top side of the roof panel into a deck. These systems are designed for high slope applications for both bare and prepainted GALVALUME roofs. Panel lengths are typically short on these systems because they do not provide for expansion and contraction from temperature changes. These systems also require many overlapping joints which must be properly sealed to avoid crevice corrosion.