CGI was invented in the 1820s in Britain by Henry Palmer, architect and engineer to the London Dock Company. It was originally made (as the

name suggests) 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) the most 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 two or three corrugations, and a vertical overlap of about 150mm, to provide for waterproofing. CGI

is also a common construction material for industrial buildings throughout the world.

Wrought iron CGI was gradually replaced by mild steel from around the 1890s, and iron CGI is no longer obtainable - however, the common name

has not been changed. Galvanized sheets with simple corrugations are also being gradually displaced by 55% Al-Zn coated steel or coil-painted

sheets with complex profiles. However CGI remains common.