When someone calls about a leak, the shingles are almost never the problem. Shingles in the open field of a roof are doing a simple job — shedding water downhill onto the shingle below. What fails is everywhere the roof stops being a plain slope: valleys, chimneys, vent pipes, skylights, sidewalls, and the edge details at the eave and rake.
A valley is the hardest-working part of a roof because two planes are funnelling their water into one channel. That channel carries several times the volume of the field around it, and in a Mid-Atlantic storm it carries that volume fast. Valleys need to be lined properly and the shingles cut back cleanly off the centre — a valley that has been woven badly or nailed too close to the middle will hold water at exactly the point that most of the roof is draining through.
Penetrations are the other repeat offender. Every pipe, vent and chimney is a hole cut in a waterproof surface, and the only thing making it watertight again is the flashing and the way it laps with the courses around it. Pipe boots are the classic failure: the rubber collar perishes in UV long before the shingles wear out, so a roof with plenty of life left starts leaking around a vent stack. It is a cheap fix if you catch it and an expensive one if the water has been running down the pipe into the ceiling for two winters.
Then there is ice. Freeze-thaw cycling is the thing that separates roofs here from roofs further south. Meltwater runs down a warm roof, hits the cold overhang past the wall line, refreezes, and builds a dam that backs standing water up under the courses. Shingles are designed to shed water flowing downhill, not to hold it sitting still — so water that has been dammed goes wherever gravity and capillary action take it, which is usually sideways under the laps and into the decking.
That is why we get on a roof before quoting it rather than pricing from the driveway. The decking, the flashing and the valleys tell you what the roof actually needs. Call New Generations Services at (240) 375-4853 and we will come out and look at it.