An aging roof
A roof rarely fails on a single day. It gets close over several years, and then one long wet season finds the weakest point. On the Puget Sound the aging runs on water rather than sun — a covering that never quite dries wears out from the edges and the shaded slopes inward — and it announces itself, to anyone who knows where to look.
The signs, roughly in order
The moss line comes first: growth establishing along the north slopes and shaded sections, a sign the surface is staying wet longer than it should. Granules follow — collecting in gutters as the mineral armour leaves, fastest under moss and along the eaves. The small rubber boots around plumbing vents crack in their second decade regardless of climate, and a cracked boot is often a roof’s first actual leak. Then the edges soften, ridge caps — the thinnest, most exposed pieces on the roof — begin working loose, and the covering starts reading a different age on each slope.
The useful question near the end is not “can it be patched” but “what does this year’s decision cost versus next year’s.” Replacing early forfeits a little remaining life; replacing late buys deck repair and interior work on top of the same roof. On plat-era streets where every covering went on the same season, the neighbours’ roofs are data — when the street starts turning over, an evaluation of your own is due.