Metal Roof Buckling

William Donovan
I'm getting different opinions on whether or not to install metal roofing over a single layer of asphalt. Several contractors have told me it's not necessary to remove the shingle because of the light weight of the metal. However one just told me that you did need to remove the Asphalt layer because if you installed metal over asphalt, the metal has the potential of "buckling" in the hot summer weather we're having. I've not heard that buckling is an issue with metal shingle.
David Stermer
William, Thanks for the question. There are certainly benefits to removing the asphalt shingles before installing a metal roof. Primarily, it is possible to completely inspect the sheathing to ensure the panels will be adequately attached. I have not experienced metal shingles buckling. It is difficult to imagine how metal shingles will buckle as a result of the a layer of asphalt shingles underneath. The size of metal shingles limits the amount of thermal movement they experience. If the roof surface has sagging between supports or there has been build-up so that the roof surface is not in-plane, this can cause buckling. From my perspective, the best practice is to remove the shingles, however, there have been plenty of installations over existing shingles that perform well. Regards, David Stermer, PE

If you would like to reply to this thread, please log in. If you do not have an Ask the Experts forum user account, create one here.

Find a Professional

Get Started Today

Take the first step to increasing the value of your home with a great looking, durable, fire resistant and energy efficient metal roof. Browse our list of qualified MRA Member Roofing Professionals in your area for a free consultation and estimate.