Expansion Location

Pablo Gotay
9/30/2013
I have a metal roof that is varies in length but is generally over 70' long without seams and has a gradual pitch. The installer has placed the expansion joints at the top of the ridge instead of the eave. My concern is that the coefficient of friction plus the weight of the roof itself and weight of snow in the winter will prevent the metal from expanding upward. Is this a real concern or should the install work correctly in regards to expansion?
David Stermer
9/30/2013
Pablo, Thanks for your question! The force that is required to prevent thermal expansion / contraction is incredible. It is tens of thousands of pounds for a typical panel. It is so large that it is very difficult to overcome for long panels. Instead, either the restraining fasteners will fail or the panel will fail in bearing at the restraining fasteners. The dead and snow loads are not sufficient to overcome this force. For a properly designed standing seam roof system, the friction is the system is also not sufficient to overcome this force. From my experience, standing seam roof systems work equally well whether the fixed point is located at the low end (eave) or high end (ridge) of the panel. It is important that the fixed point be rigid enough to resist the in-plane sliding force, also known as drag load, due to gravity loads, such as dead, live and snow loads. Regards, David Stermer

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