The roof is part of the exterior but requires more individual attention. It is designed to protect all the components of the dwelling. Every roof will wear differently relative to its age, the number of its layers, the quality of its material, the method of its application, its exposure to direct sunlight or other prevalent weather conditions, and the regularity of its maintenance. Regardless of its design-life, every roof is only as good as the waterproof membrane beneath it, which is concealed and cannot be examined without removing the roof material, and this is equally true of almost all roofs. In fact, the material on the majority of pitched roofs is not designed to be waterproof only water-resistant. However, what remains true of all roofs is that, whereas their condition can be evaluated, it is virtually impossible for anyone to detect a leak except as it is occurring or by specific water tests, which are beyond the scope of our service. Even water stains on ceilings, or on the framing within attics, could be old and will not necessarily confirm an active leak without some corroborative evidence, and such evidence can be deliberately concealed.
Consequently, only the installers can credibly guarantee that a roof will not leak, and they do. We evaluate every roof conscientiously, and even attempt to approximate its age, but we will not predict its remaining life expectancy, or guarantee that it will not leak. Naturally, the sellers or the occupants of a residence will generally have the most intimate knowledge of the roof and of its history. Therefore, I recommend that you ask the sellers about it, and that you either include comprehensive roof coverage in your home insurance policy, or that you obtain a roof certification from an established local roofing company.