Looking at Buildings

closeGlossary Term [1] to the mines. However timber was becoming increasingly restricted by the end of the 18th century and from that date coke and coal were employed in the smelting process, causing the industry to be concentrated in the areas where these materials were available. Once smelted the iron needed to be hammered, while hot, into its final shape. The size of the finished article was therefore limited both by the amount of smelted ore available and the speed with which the smith could achieve his work. Most wrought ironGlossary Term [2] components were therefore modest in size e.g. nails or hinges but once hardened the material was extremely durable.

Although almost all iron had to be wrought by hand, it was also possible to cast the smelted ore into shapes by using moulds. This method offered the possibility of mass production for decorative and other components and eventually entirely superseded small-scale wrought ironGlossary Term [3] production. Cast ironGlossary Term [4] revolutionised building technology from the end of the 18th century, when it was first used in a structural capacity. Its strength made it suitable for load-bearing but its brittle nature meant it was liable to fracture under tension.

Large scale production of wrought ironGlossary Term [5] for structural use was aided by Henry Cort's development of the puddling process in 1784 and the subsequent invention of mills for rolling the iron into bars and other standard components suitable for building. Its flexibility and strength under tension made it suitable for trusses and beams and in particular for wide-span structures such as bridges.

The major innovation in the structural use of metals was the discovery of steel. After c.1880 rolled steel, similar but stronger than wrought ironGlossary Term [6] was used in creating self-supporting framed structures which could be built to great heights.

Since the mid-20th century numerous other metals, such as aluminium, have also played an increasing role in different types of structure.