Why roofs fail
Six things account for most of what gets reported between the bay and the mountains. Very little of it is the shingle simply wearing out in the middle of a slope. It is edges, joints, materials, and decisions taken years earlier.
- 1 Ridge caps. Thin, fully exposed, and the first course to lift.
- 2 The field. Granule loss is the honest measure of how much life is left.
- 3 Valleys. One channel taking the runoff of two slopes, all year round.
- 4 Flashing. At the chimney, and where the garage roof meets the wall of the house.
- 5 The vent boot. Small, rubber, and on a much shorter clock than everything around it.
- 6 Eaves. Where water that has backed up at the edge gets under the courses.
The six
Repair or replace: the honest version
Most of what goes wrong on a roof is local. A boot that has split, a length of flashing that has lifted, a valley that has been holding wet leaves for two autumns: those are repairs, and a roofer who insists otherwise on a covering with years left in it is selling you the wrong job.
What genuinely ends a roof is different, and there are only two versions of it. The covering has run out of service life: granules gone, mats brittle, repairs arriving closer together each year. Or the deck underneath has been wet long enough to go soft, in which case no amount of surface work is going to hold a fastener.
The useful question to put to anyone who comes out is therefore not “how much for a new roof” but “is this the covering, or is this one spot”, and then “what did the deck feel like where you walked it”. Someone who has actually been up there answers the second question without hesitating.
What this region does to a roof
Ice damming at the eaves every winter, which pushes water backwards under the shingles while the rest of the roof still looks sound. Flashing that outlives its sealant at every chimney and vent. And a mature tree canopy over the postwar suburbs that keeps north slopes from drying and fills valleys with leaf litter. Most reported leaks here trace back to one of those three.
None of the three announces itself from the ground. Ice damming shows up as a stain on an upstairs ceiling in February and is invisible in July. Failed flashing produces a leak after ordinary rain rather than heavy rain, which is the tell most owners miss. And leaf litter in a valley does its damage by staying wet against the covering between rains, in the one part of the roof that carries the runoff of two slopes at once.
That is the argument for looking before there is anything to see. The roof age check walks the envelope part by part, and the quote comparison is for when you already have numbers in hand and cannot tell why they differ.