There is a big cost difference between replacement and re-roofing over your existing roofing system. If the existing roofing system is wet or you have 2 layers of roofing or more we must remove your roofing system. Code then requires us to install a minimum R-20 insulation system with taper if the roof doesn't have a slope in it. It is always preferable to remove the existing system to examine the roof deck (substrate). We understand that economically this isn't always feasible, therefore we offer various overlay systems depending on your financial situation.