How To Treat Overlapping Roof Sheets When Treating Cut Edge Corrosion

As everybody who has used Liquasil systems, or attended a Liquasil CPD session on this subject knows, we are not advocates of sealing gaps on overlapping metal roof sheets, when treating cut edge corrosion.

It is our strong belief (with much evidence to support), that sealing gaps with a silicone sealant creates more problems than it solves.

That is because when trafficked, the roof sheets move and the silicone splits in the middle. 

This creates a capillary action. where water is sucked in through the split (which is barely visible to the human eye) and becomes trapped behind the silicone seal, where it causes rusting from underneath the sheets - something that wouldn't normally happen if it wasn't sealed, because water entering the gap is allowed to run off.

But sometimes, we do recommend that gaps are sealed. 

For example, removing an old cut edge corrosion system where trapped water has rotted the edges of the sheets.

But we still don't recommend using silicone sealants. 

Instead, we embed a very thin, perforated, polyester fleece into our vapour permeable Flexlap coating, to bridge the gap and create an incredibly strong and permanent seal across the joint.

Water cannot penetrate the gap, but vapour can escape.

This is a particularly useful approach when the cut edge corrosion is being treated as part of a full roof coating, because the fleece hides the untidy, rotted elements of the sheet ends.

Liquasil's cut edge corrosion treatment and metal roof coating systems are BBA Approved and are the only such systems to have BBA certification for this purpose.

Liquasil's cut edge corrosion treatment includes SWT Primer, a rust treatment primer that has been extensively tested and proven over 15 years in harsh marine environments.

SWT primer is Surface and Wet Tolerant. This means it can be applied directly to red rust, even in wet conditions.

Once applied, the treated surface cannot rust.

SWT Primer dries rock hard and cannot be removed or broken without significant grinding. It is stronger than the metal to which it is applied.

When treating cut edge corrosion, you have only a small number of choices.

Only one is BBA Approved. Only one actively treats the rust. Only one can seal joints effectively.