What is cut edge corrosion? The common defect.

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What is cut edge corrosion?

Cut edge corrosion is a common defect that affects aging profiled metal roofs and is a defect we regularly find as building surveyors. From the factory, steel roof sheets are finished in a plastic based coating system which protects the steel from corrosion. The sheets are then cut into sizes to be transported and installed on site. This leaves exposed ends to the sheets which are not  protected from the weather. Once the roof sheets are installed, end, mid and side laps of the sheets are susceptible to moisture which is able to track beneath the coating through capillary action, and then begin to corrode the exposed  metal to the sheet ends and laps. This causes the coating to peel, further exposing the unprotected metal to the elements, this then corrodes, and the process repeats itself. If left untreated the condition of the affected roof sheets will continue to deteriorate and can eventually lead to corrosion through the surface, allowing water ingress.

Corrugated Roof with split

How to repair / treat cut edge corrosion?

Cut edge corrosion could be prevented by treating the cut edges with a protective coating system when the roof is installed, however in practice, this rarely happens. Depending on the extent of corrosion, cut edge corrosion can be treated with a liquid coating system. Methodologies and products differ slightly from each manufacturer. However in essence the process involves removing the corrosion and treating with an anti-corrosion primer. For a mid-laps, a gun applied sealant or butyl tape will be applied to seal the joints. The final coating will then be brush or roller applied to protect the cut edges from further corrosion. Most manufacturers offer at least a 10 year guarantee, making it a more cost effective option than re-roofing, particularly where a Tenant may only have a limited term remaining on their Lease.

Corrugated Roof with split and repair

Cut edge corrosion and dilapidations

Cut edge corrosion defects to roof sheets are included in dilapidations claims quite often. A dilapidations claim at Lease end to treat and repair cut edge corrosion can be a costly  item for the Tenant, even if they had a Schedule of Condition in place at the start of the Lease. This is because a Schedule of Condition alone does not protect the Tenant from the further natural deterioration of defects. Therefore, we always recommend that where cut edge corrosion is present at the start of a Lease that a Tenant should ask the Landlord to exclude liability for the further deterioration of the roof. Bradley-Mason LLP has a wealth of experience in dealing with dilapidations matters and producing Schedules of Condition, as well as specifying and project managing roof repair works on commercial buildings.



DISCLAIMER: This article is for general information only and not intended as advice. Each project has its own set of unique circumstances, all potential issues should be investigated by a surveyor on a case by case basis before making any decision.


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