*Directly adhering roof membranes to paper-faced polyisocyanurate insulation should be avoided wherever possible. In many of the wind-damaged roofs we’ve investigated, the membranes were applied directly to the insulation and the facer was delaminated from the board, essentially leaving the membrane detached. Loose membranes can be readily lifted, distorted or worse, blown off entirely, in even moderate winds. The use of a proper cover board between the insulation and the roof membrane can help prevent this.
*Warranties should be carefully considered before a system is selected. Manufacturers’ warranties frequently exclude damage from wind above a given speed and that speed is often much less than building code design requirements. As an example, we recently reviewed a warranty that did not cover damage from winds greater than 65 miles per hour, although the roof was installed on an oceanfront building where the design wind speeds are 130 miles per hour. This limitation is roughly half what is to be designed and is well within the “regularly” experienced wind conditions. Therefore, the warranty coverage related to wind in these cases is extremely limited or even non-existent.
*Many roof material manufacturers have added self-adhered membranes to their product lines. While there are advantages with self-adhered products, surface preparation is critical and adhesion is greatly affected by temperature. The use of primers can help with the bond.
It seems that weather is becoming more severe and there’s no reason to think that trend is going to change. Prior to June 2012, few people had ever heard the term “derecho”, much less lived through one. It’s impossible to anticipate every eventuality and no way to practically design for them. However, consulting a roof professional when replacing your roof can help avoid these and other pitfalls.