October 24, 2018
Standing seam roof (SSR) systems are built to move, designed to account for necessary—and often substantial—expansion and contraction due to thermal conditions. In fact, for many builders, this fact is one of the main reasons SSRs are such an attractive option.
Even with this expectation baked into the mix, many contractors and installers may still make a wrong turn when tying the SSR into adjacent structures and other building edge conditions. By not allowing for that same expansion and contraction on trims and transitions, problems can ensue.
One main consideration in planning for this movement is the clip type used. Standing seam metal panel clips are designed specifically to interact with their corresponding roof panels in order to allow movement (both interior and exterior) caused by thermal changes. The clips, which are part of the concealed fastening system used with SSRs, provide improved aesthetics in addition to durability and protection from the elements.
The two main options are fixed clips (one-piece) and floating/sliding clips (two-piece). Fixed clips are limited by and dependent on the substrate’s ability to expand and contract with the roof system, whereas floating/sliding clips permit the panels to expand and contract within the clip itself. These clips will allow for greater thermal movement of the panel, which is independent of the substrate while still ensuring the panel remains secured. Regardless of which clip is utilized, you are not going to stop the expansion and contraction. You can, however, have some control of the direction of movement, and, therefore, can address or compensate for the degree of this movement when tied into adjacent structures.
Standing seam roofs with floating/sliding clips require one end of the panel run to be “pinned” and the other end to be “moveable” in order to permit expansion and contraction. The “pinned” point of the system is typically the low eave, although it doesn’t have to be. There will be instances when it becomes beneficial to “pin” the roof at the complicated transition or tie-in point and design the roof system to expand/contract outward from this location. This can eliminate potentially “troublesome” areas from the equation on having to deal with the roof movement, and in turn can make them easier to install and have greater weathertightness success.
With all this in mind, it is important to always check with the manufacturer to determine the best clip and design layout to use with any given SSR system and be aware of how much and in what direction the expansion and contraction is going to occur.
Not only does the building move, but anything it ties into has to be able to permit that movement, e.g., the edges or perimeter of the buildings. Manufacturers can provide both longitudinal and transverse transitions that allow for thermal movement so that when they tie into an adjacent structure it doesn’t restrict the panel from moving. Not adequately compensating for or preventing that movement entirely can lead to potential pitfalls, such as oil canning. It could also lead to fasteners backing out and slotting of holes. Bottom line, any time that we try to confine or restrict the roof from doing what it was meant to do (move!), we inevitably run the risk of damaging the panel not just aesthetically but more importantly, from a weathertightness standpoint.
Issues can arise not just when tying panels into adjacent structures. Because of the roof’s size and magnitude of potential movement, you may/will have to implement expansion/contraction capability of various degrees into the perimeter of the roofing system itself. In these cases, this is why manufacturers offer roof accessories as ridge expansions, edge trim expansions, panel expansions, gutter expansions and other details to account for not only the roof movement but the perimeter trims that are secured from the roof system to the wall system.
The key takeaway here is to remember that if you’re considering a standing seam roof for a project, then you need to make sure that the designer looks at every detail from the manufacturer and accounts for movement of the roof panel, such as how it ties into adjacent structures or simply how the edge or perimeter of the building is terminating to make sure they permit that expansion and contraction. Know what you’re buying and understand that if the roof you’re purchasing is meant to expand and contract, everything that ties into it has to be able to expand and contract as well.
To find out more about how to correctly install your standing seam roof, contact your local MBCI representative.