Insulation The roofing insulation must be kept dry at all times and must be dry at the time of installation and at the time of roofing membrane application. No more insulation shall be installed at any one time than can be protected by bitumen and felt in case of sudden weather changes. Edges of insulation shall be brought closely together and shall not be forced into place. Mechanically fastening through 2 or more layers of insulation is not permitted. When more than one (1) layer of insulation is used, joints in each layer shall not coincide. All layers shall be parallel to preceding layers and staggered a minimum of 6".  Return to Application Considerations and Specifications