Cut Edge Corrosion: The Warning Signs on Your Roof
What cut edge corrosion looks like in its early stages, and why catching it before perforation is the cheapest roof decision you can make.
Of all the ways an industrial metal roof fails, cut edge corrosion is the most predictable, and the most preventable. It follows the same pattern on almost every roof, which means if you know what to look for, you can catch it years before it starts letting water in.
Where it starts
When profiled metal sheets are manufactured and cut to length, the cut edges are left exposed, the protective coating does not wrap around them. Those exposed edges are at the eaves (the bottom of each sheet) and at every overlap between sheets. Weather attacks the bare metal there first.
The warning signs, in order
Cut edge corrosion progresses in stages:
- Rust staining streaking down from the sheet ends and laps
- Flaking and lifting of the coating along the exposed edges
- Surface rust spreading up the sheet from the cut edge
- Perforation, at which point the roof is leaking and the sheet may need replacing
The cheap, easy intervention is at stages one and two. By stage four you are into sheet replacement rather than treatment.
Why early treatment pays
Cut edge corrosion treatment, cleaning back the affected edges and sealing them with a specialist coating, is inexpensive compared with replacing perforated sheets, and it can add years to a roof’s life. The whole economic argument rests on catching it early.
When to look
If your metal roof is more than 10 to 15 years old and has never had its cut edges treated, it is worth an inspection, ideally before the wet season, when treatment is preventative rather than a response to a leak. Get in touch and we will take a look.