I'm often asked how many years a customer may expect to get from a roof systems installed on the home they want to purchase. Estimating, or perhaps a better term would be guesstimating the life of a roof system accurately is nearly impossible and most inspectors won't want to make such a statement. There are far to many variables to make any kind of reliable prediction. For example:
Was the roof system installed incorrectly? How long has it been installed? Are there trees over the roof? What kind of roofing was used? Was a membrane installed under the roofing? Will one side of the roof weather faster than the other? Is there adequate insulation installed in the attic? From what direction do the prevailing winds come from? The list of variables goes on and on. A home inspector is performing a visual inspection of the roof system on the specific day and cannot give a customer a reliable time when the roof will fail. What an inspector can tell a customer is if roof systems defects, leaks and wear are visible to inspection at that time. Now having said that, some conclusions can be be assumed by the customer. Roof system defects, example: (valleys,penetrations,antennas,improper flashing's,sags, inadequate insulation and many more) can all shorten the life of a roof system. Wear indicates that much of the roofs normal life has been used. Leaks indicate that the roof system has failed.