Wet winters, steel roofs and a predictable failure point
Devon catches some of the wettest weather in England, and profiled steel roofs around Exeter feel it at their weakest detail first. Steel roof sheets are cut to length when they are made, and the cut exposes bare metal at every sheet end and overlap. The factory coating protects the face of the sheet for years; the cut edge was never protected at all. Rust starts there, then burrows back under the coating, peeling it away as it advances.
That is cut edge corrosion, and on the trading estates around the city and the farm buildings across the county it is one of the most common reasons coated steel roofs leak before their time.
How a stained edge becomes a holed sheet
The defect feeds on moisture, and Atlantic weather supplies it for months at a stretch. Side and end laps draw rainwater in by capillary action and hold it against the bare steel, so the joint stays wet long after the roof surface has dried. As the rust expands it delaminates the coating, the curled edge traps more water, and the corrosion front climbs the sheet. Left to run, the steel thins until it perforates, usually at the eaves or an end lap, and usually first over whatever you least want rained on.
The case for treating it this year, not next
Early treatment is a contained, surface-level job: mechanical preparation of the corroded edges, a corrosion-inhibiting primer, sealed laps and a flexible coating band over the edge zone. It addresses the cause, and the building stays open while it is done.
Every season of delay moves some of the roof closer to the point where treatment stops working. Replacement sheets, access equipment and disruption cost many times more than an edge repair, and the difference between the two outcomes is usually just timing. With this defect, early really is cheaper, and not by a small margin.
When we will not recommend coating
Our surveys sometimes find roofs near Exeter that are past treatment: sheets already holed, laps with serious metal loss, or corrosion eating the underside where no coating can reach. We will not quote a treatment for steel that is no longer there. In those cases we set out what we found, with photographs, and the realistic options: replace the failed sheets and treat the rest, or move to an overlay or full re-sheet. A coating company that says yes to everything is not one you should trust on a roof.
Edge treatment as part of a bigger answer
Cut edge corrosion usually shows up on roofs whose coating is ageing everywhere, not just at the edges. If the sheet faces are chalking, fading or cracking, treating the edges alone leaves the next failure in place. A full roof coating with cut edge treatment built in protects the whole surface in one programme and is often the better long-term spend.
- Rust staining at the eaves or in the gutters
- Coating lifting or curling at the overlaps
- Rust rings spreading around fixings
- Damp patches inside the building below sheet ends
Any of those is a reason to book a survey rather than wait for a leak. We are based in the South-East and work England-wide, covering Exeter and the wider South West, with every recommendation grounded in what the survey actually finds.
