If you’ve got a profiled steel roof on a factory, warehouse or industrial unit, look at the bottom edges of the sheets and along the overlaps. If the coating is peeling back and there’s rust creeping in from the edge, that’s cut-edge corrosion — and it’s the most common reason metal roofs start to leak. The good news is that, caught in time, it’s very treatable. You don’t need a new roof. You need the edges dealt with properly.
What causes it
Most profiled metal roof sheets are steel with a protective organic coating on both faces. When the sheets are cut to length at the factory, the cut edge is left with bare steel exposed. For the first few years that’s not a problem. Over time, though, moisture sits at the eaves and in the end laps, the steel starts to corrode at the edge, and the rust gets under the coating and lifts it — the coating delaminates and peels back, and the corrosion spreads up the sheet. Once it reaches the laps and fixings, water starts getting in.
It tends to be worst on the north-facing slopes, at the eaves where water collects, at end laps on long runs, and around anything that holds moisture — gutters, rooflights, and debris left on the roof.
Signs to look out for
- Peeling coating — the paint or plastisol finish lifting at the edges of the sheets.
- Rust staining — orange or brown streaks running from the laps and eaves.
- Leaks at the laps — drips inside along the lines where sheets overlap.
- Corroded fixings — rusty screw heads and failing washers, often at the same time.
- Weeping gutters — the gutters underneath often corrode at the same rate as the sheet edges.
How we treat it
A proper cut-edge treatment isn’t a coat of paint. Done right, it goes like this:
- Survey — we inspect the whole roof, not just the obvious edges, and check whether the sheets themselves are still sound enough to treat. We’ll tell you straight if they’re not.
- Preparation — loose and delaminated coating is removed, corrosion is taken back to sound metal by wire brushing or abrasion, and the area is cleaned and degreased.
- Prime — a rust-inhibiting primer is applied to the prepared steel.
- Seal — a purpose-made cut-edge sealant or liquid coating system is applied across the edges and laps, often with a reinforcing tape or membrane at the end laps, to seal them against water.
- Fixings — corroded fasteners are replaced or capped, and failed washers sorted.
- Finish — a top coat colour-matched to the roof where needed, so the treated areas don’t stand out.
We’ll often pair this with gutter lining and rooflight replacement, because they tend to fail at the same time and it’s cheaper to do them on one set of access.
Why treat rather than replace?
Because it’s typically a fraction of the cost of re-sheeting, with far less disruption. There’s no stripping of the roof, no exposing the building to the weather, and no skips full of old sheets. Most of the work can be done with the building in full use. On a lot of roofs it adds many years of life — and a good number of treatment systems come with manufacturer-backed guarantees when they’re installed correctly.
It isn’t always the answer. If the sheets are corroded right through, or the roof needs insulating to current standards, then over-sheeting or a strip-and-resheet is the better investment — and we’ll show you why rather than just telling you.
Where we work
We carry out cut-edge corrosion treatment on factory, warehouse and industrial unit roofs right across the West Midlands, including:
- Commercial roofing Birmingham
- Commercial roofing Redditch
- Commercial roofing Coventry
- Commercial roofing Walsall
- Commercial roofing West Bromwich
- Commercial roofing Wolverhampton
- Commercial roofing Worcester
- Commercial roofing Solihull
Questions we get asked
How long does cut edge corrosion treatment last?
It depends on the system and the condition of the roof, but properly prepared and applied treatments regularly give many years of extra life — and many come with a manufacturer-backed guarantee. We’ll tell you what to expect for your roof after the survey.
Can you treat the roof while we’re still working inside?
Yes. The work is all done from the outside, so the building stays in use. We plan access, edge protection and any noisy preparation around your operation.
Is cut edge corrosion covered by the original roof guarantee?
Sometimes, on newer roofs — it’s worth checking your paperwork. On older roofs the original guarantee has usually expired, which is when treatment becomes the cost-effective route.
How much does it cost?
It’s priced on the length of edges and laps to be treated, access, and what else needs doing at the same time. After a survey you’ll get a fixed written price. It’s typically a fraction of what re-sheeting would cost.
Rust creeping in from the edges of your roof sheets? Call 0121 592 0293 for a free survey. We’ll tell you honestly whether it can be treated, and give you a fixed price.
