Cut edge corrosion is the result of a design fault in the manufacture of coated metal cladding sheet types such as Plastisol and Pvf2 amongst others. The cladding is factory coated to protect it from weather damage and corrosion but also for appearance purposes.
In the past, cladding manufacturers would only guarantee their cladding for 15 years but due to more recent developments in technology and much improved coating systems, manufacturers such as Kingspan can offer their cladding with a 25 year warranty.
However, when these sheets are cut to size off the factory roll, prior to a builder using them in construction, this cut exposes a thin line of metal which isn’t coated, thus not protected in the same way as the rest of the sheet. Effectively, the cut edge of the metal cladding sheet is the achilles heel and the area of the roof most likely to succumb to peeling and corrosion.
The metal can also expand which causes the factory coating to lift, exposing the metal further. This can eventually lead to the whole coating delaminating which will make it very easy for the existing corrosion to eat through the metal completely, causing leaks within the premises. If this happens, the affected cladding sheets will need to be replaced.
Weather also plays a major factor in the lifespan of cladding, specifically when it comes to cut edge corrosion. The constant moisture from the cold and wet weather promotes corrosion which is why you would rarely find cut edge corrosion in a hot climate country like Australia.
What is the solution?
The ideal solution would be for the manufacturers of the cladding to coat the cut edge after the cut, so that no metal is exposed at all, or move to Australia. However, that doesn’t really help those with existing metal cladding roofs in England and even if manufacturers did start doing this, it wouldn’t solve the problem completely as there are still millions of square meters of cladding on roofs right now.
The actual workable solution is to apply the repair system to existing roofs and guarantee against corrosion or peeling for the next 10 years.
What does this involve?
The process is actually quite straight forward if you follow the steps on the specification provided by the system manufacturer;
- Inspect and measure the site
- Mechanically remove corrosion
- Feather back the peeling to smooth the surface out and remove any ridges
- Apply the system