Even in winter, immediate replacement of roof systems could be an absolute necessity, depending on the severity of leaks and the interior environment the roof is supposed to protect. Contingent on the size of the roof, its complexity, and contractor availability, there may be time to squeeze in the replacement before snow falls. While roofing can be performed during the cold, winter months, there are many challenges that must be addressed by designers, contractors, and owners. These difficulties can be amplified when reroofing over an occupied facility.