Durability

The durability of metal cladding is a major factor in the both the design and specification of a system. Durability is influenced by the type of material, exposure of the panel, local environmental factors, corrosion protection systems and detailing.

The durability of a cladding system is often defined in terms of period to first maintenance when repainting is likely to be necessary.

The durability of a cladding system requires careful consideration. It is often associated with manufacturer’s warranties. It therefore must be clearly defined. In the use of metal cladding the life of a system is general defined in terms of its period to first maintenance, the period after which the material may need repainting to maintain its original appearance or original coating system no longer protects the substrate underneath. At this point re-painting is likely to be necessary.

Suppliers of aluminium and protected steel will provide detailed information on the durability of their products correlated against standard weathering tests and experience.

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The durability of claddings is sensitive to the environmental conditions at the location of the building, application, detailing and workmanship. The British Standard BS 5427 identifies three primary location types, coastal, industrial, and rural. The latter being the most benign. Coatings are also affected by the intensity of exposure to ultraviolet radiation and some colours have pigments that are better than others at blocking UV rays. Roofs will experience more prolonged exposure to solar radiation than walls, although south facing walls will also experience prolonged exposure compared with other orientations. For organic coated steels the period of to first maintenance can be as long as 30 years but will reduce depending on the factors considered above. The coatings on aluminium cladding may expect a similar life span although failure to repaint will not affect the overall life of the cladding but will preserve the appearance.

The durability of steel cladding systems may also be affected by workmanship related defects such as scratching the coating during installation. The cut edge at the end-lap of sheets is also sensitive and deterioration is likely to be first noticed here, before general deterioration of the coating. Turning down the end of the cut sheet can improve the durability of this detail, by preventing drips collecting.