Drops can form under the steel sheet of an open shelter even when it is not raining. This is the result of vapour condensing on cold metal. An anti-condensation layer can retain some of this water and reduce dripping. However, it must dry out afterwards. It is not insulation or a repair for a leaking roof, and its performance depends on the conditions beneath the covering. Air contains water vapour. When its contact with a cold surface leads to condensation conditions being reached, condensate forms on the underside of the metal. In an open shelter this can occur after the covering has cooled overnight. It does not automatically mean a hole or a poorly closed lap.

Before ordering the sheeting, establish the environment the roof will face — the coating should be chosen on that basis, not on colour alone. Check which protective layers the sheet has and whether their intended use suits conditions by the sea, at an industrial site or inside a farm building. During installation, watch the edges, swarf and fixings, since corrosion most often starts there. A single rusty spot does not necessarily mean the steel is damaged, so before any repair it is worth identifying the source and extent of the change.