Sun and heat
Most of the country gets a summer. This coast gets ultraviolet exposure twelve months a year, and ultraviolet light is precisely what ages an asphalt shingle: it dries the asphalt, loosens the granules that shield it, and turns a flexible covering brittle. A shingle rated for thirty years in a laboratory rarely gets there here.
- 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.
How the damage reads
The sequence is consistent and readable from the ground if you know it. First the granules go: collecting in the gutters, leaving the surface looking faded and slightly rough. Then the exposed asphalt dries and the edges curl or cup. Finally the material becomes brittle enough that ordinary thermal movement cracks it. On a Florida roof this runs faster on the south and west slopes, which take the afternoon load, so the two halves of one roof can read as different ages.
The second, quieter half of the problem is underneath. A roof surface in direct summer sun here runs far above air temperature, and an attic that cannot exhaust that heat holds it against the underside of the deck. The covering then ages from both sides at once, which is why two identical houses on the same street can retire their roofs years apart based on nothing but ventilation.
What actually helps
Color and reflectivity make a measurable difference on cooling costs and a smaller one on covering life. Balanced ventilation makes the larger difference and costs less. And on the tile roofs common here, the sun is almost irrelevant to the tile itself. It is the underlayment beneath, out of the light entirely, that ages and decides when the roof needs work. Knowing which material you have therefore changes what you should even be looking at.
Want this looked at?
Call (866) 227-2038Say what you have noticed and you will be connected with a provider covering your county.