Corrugated iron

Corrugated galvanised iron or steel (colloquially corrugated iron (near universal), wriggly tin (taken from UK military slang), pailing (in Caribbean English), corrugated sheet metal (in North America) and occasionally abbreviated CGI) is a building material composed of sheets of hot-dip galvanised mild steel, cold-rolled to produce a linear corrugated pattern in them. The corrugations increase the bending strength of the sheet in the direction perpendicular to the corrugations, but not parallel to them. Normally each sheet is manufactured longer in its strong direction.

CGI is lightweight and easily transported. It was and still is widely used especially in rural and military buildings such as sheds and water tanks. Its unique properties were used in the development of countries like Australia from the 1840s, and it is still helping developing countries today.

Corrugated iron is equivalent to tin roof.

CGI was invented in the 1820s in Britain by Henry Robinson Palmer, architect and engineer to the London Dock Company. It was originally made from wrought iron. It proved to be light, strong, corrosion-resistant, and easily transported, and particularly lent itself to prefabricated structures and improvisation by semi-skilled workers. It soon became a common construction material in rural areas in the United States, Chile, New Zealand and Australia and later India, and in Australia and Chile also became (and remains) a common roofing material even in urban areas. In Australia and New Zealand particularly it has become part of the cultural identity, and fashionable architectural use has become common.

For roofing purposes, the sheets are laid somewhat like tiles, with a lateral overlap of one and half corrugations, and a vertical overlap of about 150 millimetres (5.9 in), to provide for waterproofing. CGI is also a common construction material for industrial buildings throughout the world.

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