It is important to allow unlimited thermal movement in a metal roof system so that the panel can expand and contract without restriction. With continuous panel runs of over 100 feet, which is possible with R-Mer Span, the panel can move up to two inches as the ambient temperature rises and falls. Different metals expand at different rates. Some metal, such as aluminum and zinc expand twice as much as steel. R-Mer Span is available in a number of metals such as steel, aluminum, zinc, copper and stainless steel.
If the panel is restricted by the clip or fasteners when the expansion occurs the panel will buckle and billow. This will increase the oil canning effect that is common with standing seam panels, as well as potentially damage the panel and/or its clips.
A two piece clip design will allow a metal panel to move about an inch, which is usually sufficient for panel lengths of up to 60 feet. The problem with this design is often created during the installation of the clips. Two piece clips consist of a base that is fastened to the deck and a second vertical piece that slides up and down in the base. The ideal position of this second piece when installed is in the center of the track. This allows the clip and the panel to expand and contract up and down throughout temperature changes. When the clip is installed, gravity pulls the sliding piece from the center position to the down-slope position. The panel is installed over the clips that are now in the down-slope position and cannot expand any further toward the eave of the roof when temperatures rise. This will create binding of the clip, which will cause the panel to billow and oil can, or possibly fail entirely. Another risk factor of the two piece clip design is that the sealant creating the water-tight seal between the clip and the panel can be damaged when the clip binds during movement. The damage of this sealant will eventually allow water to penetrate the roof system.
R-Mer Span has a one piece clip design that isolates the clip from the factory applied sealant. This allows the panel to slide freely over the clip for unlimited distances. The one piece clip is yet another factor that sets our panel apart from the majority of the competition. There is no binding of the clips, the panel can move freely over the clip for an unlimited distance, and the factory applied sealant is isolated from the clip so that it will not wear down over time.
R-Mer Span’s unique design allows for truly unlimited thermal expansion and contraction.