Flashing failure
A roof almost never gives out in the open field. It gives out at the transitions — where shingle meets chimney, wall or vent — because those joints depend on metal flashing and sealant, and on the Sound they spend eight months of the year wet, under debris, without a real chance to dry.
Why the joints go first here
Sealant ages fastest where it stays damp, and a joint under needle litter or moss edge is damp from October to May. Near the water, salt air adds its own tax: flashings, vent caps and fasteners corrode years ahead of their inland twins, so a shoreline roof can have a healthy covering and failing metal at the same time. And on the region’s remodel-heavy older stock, the joint between an original roof and a later addition is the most failure-prone line on the house — two roof generations, one bead of sealant holding the meeting.
The leak that follows rarely shows up under the failure: water travels along framing before it drips, so the stain appears a room away from the open joint. This is the honest reason “the roof leaks” and “the roof is worn out” are different diagnoses — a failed step flashing on a mid-life roof is a flashing job; the same failure on a moss-eaten, edge-soft covering is the roof telling you its age. Distinguishing the two is most of what a good inspection is for.