One of the most durable and weathertight roof systems available in the industry, standing seam metal roofs are hailed for their versatility and ability to accommodate thermal contraction and expansion caused by temperature fluctuations.
By: Ken Buchinger and Robert A. Zabcik, PE, LEED AP BD+C, NCI Building Systems with Robyn M. Feller
When a design requires a roofing system that is both aesthetically pleasing and structurally sound, architects are increasingly choosing standing seam metal roof (SSMR) systems for both commercial and residential applications, particularly high-end retrofits and new roof installations. One of the most durable and weathertight roof systems available in the industry, SSMRs are hailed for their versatility and ability to accomodate thermal contraction and expansion caused by temperature fluctuations-that is, of course, when they are installed correctly, accounting for fixity issues and with the aid of specialized accessories to keep things moving in just the right way.
Unlike other types of roofing systems, SSMRs are not attached to the substructure with exposed fasteners. Instead, the raised panel seams are attached to the substructure with exposed fasteners. Instead, the raised panel seams are attached to the substructure with a hidden clip that holds the panels to the substructure. Floating versions of these systems leverage this connection to allow the panels to float as they experience thermal movement. It should be noted that details discussed in this paper are for use with single-skin standing seam roofs, and not for insulated metal panels, which handle temperature differentials in a different way.
One of the main reasons floating standing seam roofs were developed was to accommodate the thermal movement that naturally takes place as metal roofs experience material temperature change. Typically, this is accomplished by using a sliding clip with a top portion that moves along with the roof, and a bottom or base portion that is anchored to the substructure and remains stationary. The roof panels are fastened to the substructure at either the eave or the ridge and can “float” in the direction of the unfastened end.
Installers and sometimes even designers inadvertently float both ends buts this can usually be fixed in the field or mitigated by the inherent friction in the system. For low-slope roofs, friction caused by the imperfections in the system are often enough to make the system perform as intended. Generally speaking, it’s a judgment call, so in that scenario it is wise to consult the manufacturer. However, a more serious mistake is to fasten to the substructure at both ends, preventing the roof from floating and leading to unpleasing aesthetics in the best case and failure of the weather envelope in the worst.
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