Tear-Off   FAQ's Most local roofing codes allow a maximum of two shingle layers because of the difficulty of chopping through in case of fire Manufacturers will not guarantee their products if used to reroof over a worn layer of shingles A tear-off gives you the cleanest flattest look possible Structurally unsound homes may not handle the weight of additional layers Excess heat can reduce the life of new shingles Cupped and curled shingles or wood deck replacement makes a tear off necessary for professional results