Wolverhampton’s industrial buildings range from the old factory units, built when the Black Country still made everything Britain bolted together, right up to the modern distribution sheds near the motorway junctions. Most of them have profiled metal roofs, and on roofs of a certain age, one fault always shows up: rust at the cut edges of the sheets.
Rust at the sheet ends: the mechanics
Coated steel sheets get their protective finish at the factory, but that happens before they’re cut to length. Every cut exposes bare steel at the sheet ends and along the side laps. Water gets into those overlaps and just sits there. The unprotected edge starts to rust, and that corrosion then works its way under the factory coating, lifting it off the metal. It’s a built-in problem, not a sign of a bad roof, and it shows up eventually on most coated sheet roofs after twenty or more winters.
Why it never stays where it starts
The real danger with cut edge corrosion is how it spreads. Surface rust on the face of a sheet tends to stay put. Rust under the coating keeps moving, because the lifted finish traps moisture against fresh steel. A lap showing a centimetre of staining this year can be delaminating across a hand’s width in just a few seasons. Once any part of the sheet perforates, water’s straight into your building. Around Wolverhampton, we often find perfectly sound-looking sheets with serious corrosion hidden inside the laps, especially on roofs that have been patched and re-fixed over the years. That’s exactly why we survey first, every time, before we even think about pricing. The visible edge only tells part of the story.
What treating it early looks like
Catch it before the steel is properly damaged, and treatment is a methodical job, not a huge project:
- We clean the affected edges and laps right back to sound, stable material.
- Then we treat and stabilise any remaining rust, so it can’t spread.
- We seal the lap joints properly, stopping water from sitting against bare steel.
- A flexible, purpose-made coating goes over the sheet ends.
- Finally, we photograph and record the work for your maintenance file.
It pays to get in early. Edge treatment on a stained but solid roof costs a fraction of what you’d pay for sheet replacement once it starts perforating. Replacement also means disruption: scaffolding, downtime, and making good whatever the water got to inside. Two identical buildings can be just a few years apart on this curve and face very different bills.
Where we draw the line
We won’t sell you edge treatment if your roof won’t benefit from it. If the sheets are holed, if the coating is coming off across large areas of the sheet face (not just at the laps), or if the steel has visibly thinned, then treatment is just money spent delaying the inevitable. In those cases, replacing the damaged sheets is the right answer, and we’ll say so plainly in our survey report, even if that work goes to someone else. More often, it’s a mixed bag: most of the roof is treatable, but a few sheets are past saving. An honest scope reflects that split, rather than rounding it up or down.
While the access is up: the whole-roof question
If cut edge corrosion has taken hold, the rest of the roof finish is usually weathered too. It’ll be faded, chalking, and nearing the end of its protective and decorative life. Treating the edges and then coating the entire roof as one system tackles both problems in a single programme. It also spreads the cost of your access equipment across the whole job, instead of paying for it twice. We’re a survey-led coating contractor, based in the South East but working across the UK. Wolverhampton and the wider Black Country are well within our normal patch. If your roof is showing cut edge corrosion, our survey will tell you honestly which side of the line it sits on.
