Summer rain and valleys
For four months a year, most afternoons end in a downpour. A valley, the channel where two slopes meet, carries the runoff of both at once, which makes it the busiest square foot of any roof here and the least forgiving of anything sitting in it.
- 1 Ridge caps. Full sun, no shade, ever. They cook before anything else on the roof does.
- 2 The field. Shingle, or tile sitting on felt that is doing the actual waterproofing.
- 3 Valleys. Two slopes emptying through one line, every single afternoon.
- 4 Flashing. The metal salt air finds long before it touches the covering.
- 5 The vent boot. Rubber baked brittle by sun, and the bay area’s most ordinary leak.
- 6 Eaves. Where the Florida room ties in, and where the hardware corrodes first.
Volume, and what slows it
Florida rain does not arrive gently. A single afternoon can deliver more water in an hour than some markets see in a week, and every drop from two slopes funnels through one line. A valley that is clear handles it. A valley holding oak leaves, pine needles or the fine debris that accumulates under any canopy becomes a slow, permanently damp channel, and in this humidity, damp is what everything else follows.
What follows specifically: shingles in the valley stay wet and lose their granules early, algae establishes along the edges, the valley metal corrodes from underneath, and in a heavy downpour the slowed water backs up sideways under the courses on either side. None of it is visible from the ground once the debris settles in.
Construction and maintenance
Open valleys with metal in them shed both water and debris far better than woven or closed-cut valleys made of shingle alone, and in a climate with this rainfall that is a durability decision rather than a style preference. On a replacement, ask which is being built and why. Between replacements, the rhythm on any treed lot is simple and effective: clear the valleys and gutters before the rainy season starts, not after it ends.
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