- If there is phenolic foam insulation next to a metal deck. This rusts the deck out. There may be money from lawsuits available. Contact a national company called Roof Options (877)460-7663 www.roofoptions.com if you find yourself in this situation.
- If the interior of the building generates moisture (pool, sauna, etc.) and there is no vapor barrier.
- If the height of adding a new roofing system on top of an existing one causes problems at the roof edge, with roof top penetrations or units and it would cost more to raise them than to rip the existing roofing.
- If there are structural issues within the roofing system such as bad blistering or buckling insulation, or ponding water. In some cases buckling insulation can be mitigated by fastening the buckling areas (as long as no moisture is present).
- If the additional weight of another roofing system will cause excess load on the structure (a licensed engineer should determine this).
- If there is expanded polystyrene insulation (like foam coolers from a grocery store) installed next to the roof deck (which during a fire melts at low temperatures and can cause the flame to spread).
- If the manufacturer of the roofing system being installed requires the existing roof to be removed. This is a requirement of some manufacturers to obtain a long term warranty (25-30 years).