Layers of Roofing, How many are allowed on my roof?
I've been asked, "Can we install another layer of roofing over the existing?" The answer varies with every building and project. It is advised that you seek out the local building department for theexact amount of layers that are acceptable in your area. Every city and county vary with their own codes. Steep sloped roof products such as tile, slate, metal and shakes only allow one layer. Asphalt shingles typically can have one more layer added over the top (two roofs total).