Annually thousands of square metres of metal roof cladding and flashings are damaged (often irreparably) on buildings by tradesmen indiscriminately using the roof cladding as a working platform. Such damage is not exclusive to new builds. Damage ranges from destruction of the protective coatings through to mechanical damage of the profile and flashings.
On new builds the roofs of shopping centres and commercial buildings are particularly prone to damage from wet trades, glazers and installers of ancillary plant such as extractors, signage and antennas. The wet trades are the worst offenders. They habitually stack building materials without any regard to the position of supporting steelwork or to crushing the ribs of the cladding and have a total disregard for the decorative and protective coatings on the cladding. Aluminium cladding is most susceptible to mechanical damage under these conditions. Wet cement products are particularly damaging to aluminium, aluminium-zinc and painted coatings. Brick fragments and other building debris are equally damaging to all coatings. The use of duckboards and waterproof covers will help to eliminate this problem. Scaffolding components are regularly dragged across roofs and thereby inflicting mechanical damage. The bases of scaffolding towers need to be located directly over supporting steelwork or provided with load distributing pads.
It must be remembered that all roofing systems, are in terms of SANS 10160 Part-2, designed as inaccessible i.e. to support the loading imposed during installation and maintenance only. Flashings are not intended to be used as walkways.
With all buildings the placement of components or plant on timber dunnage, be it temporarily under damp conditions or permanently, can greatly accelerate the rate of corrosion of the cladding. Another problem is swarf, the fragments produced when components are drilled or cut, as well as discarded metal objects such as screws, rivet mandrills, etc. which if not removed on a daily basis can lead to accelerated corrosion of metal coatings and staining of painted coatings. Hot swarf from cutting with friction saws or abrasive disks damages both metallic and painted coatings. This form of cutting should not be used over unprotected cladding.
Loading from the placement of air conditioning units, solar heaters and PV panels on metal clad roofs needs to be supported on a proprietary support system approved by the manufacturer of the cladding system or by a sub-assembly, preferably directly beneath the cladding, attached to the structural supporting steelwork. This will also apply to the anchoring of supporting guys to antennas.