Some roofers may suggest removing the old roof before re-roofing, while others may recommend placing new shingles over the existing roof. This decision depends on several factors, including local codes and how the roof is built. Be sure to discuss this with your roofer so you know what to expect. Some insurance companies have a limit to the number of roofs that can remain on the structure for policy eligibility. Too many layers and your insurer may non-renew your policy.