Salt air on the metal
On the Pinellas beaches, in Dunedin, along the bay shore, there is a corrosive agent working on every roof that inland houses simply do not deal with. Salt carried in the air is selective: it barely touches the shingle field, and it steadily destroys everything metal on the same roof.
- 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.
What it attacks, in order
Fasteners first: the nails and screws holding flashing and accessories down, often the thinnest metal on the roof. Then vent collars and pipe boots, whose metal bases corrode while the rubber above them cracks in the sun. Then step and counter-flashing at walls and chimneys. Then drip edge and gutter hardware. The pattern is consistent: the roof fails at its junctions and its edges, while the field in the middle looks reasonable enough to make an owner doubt the diagnosis.
Distance matters more than most people expect. A house six blocks inland ages noticeably differently from one on the water, and the effect drops off quickly, which is why a contractor who works both sides of a coastal city will price the same roof differently by address.
What to specify near the water
Corrosion-resistant materials are the entire answer and they are not expensive relative to the job: aluminum or coated steel flashing rather than plain galvanized, stainless or coated fasteners, and vent components rated for coastal exposure. On a replacement, insist that flashings, vents, drip edge and fasteners are listed as replaced rather than reused, a quote that treats them as incidentals has not accounted for the address. And between replacements, the coastal inspection habit is to look at the metal every few years rather than to look at the shingle when a stain appears.
Want this looked at?
Call (866) 227-2038Say what you have noticed and you will be connected with a provider covering your county.