The Industrial Revolution gave rise to a new building type: the factory, where a managed workforce could operate machines that were driven by steam power. The advent of machines also created a demand for iron to be produced on a large scale; in addition to being used to build machines, it soon became apparent that iron could be used to construct industrial buildings. The forerunner was the prefabricated cast-iron bridge at Coalbrookdale, England, of 1775–1779. But the factories, especially textile mills, involved problems other than the structural ones. Because they handled large quantities of cotton, flax, and wool, and because their wooden floors were quickly saturated with the oil used to lubricate the machines, they presented a fire hazard. The earliest textile mills had timber floor and roof framing and solid masonry external walls. Cast iron was non-combustible, and it was believed that it offered, as well as greater strength, a measure of fire resistance. Designed in 1795 and built the following year by the
engineer Charles Bage of the milling firm of Bennion, Bage, and Marshall, the Ditherington Flax Mill, in the Shropshire town of Shrewsbury, was the world’s first iron-framed building, the predecessor of most modern factories and even office blocks.
Ditherington was the largest flax mill of its day and one of the largest textile mills of any kind in Britain. The five-story building has conventional load-bearing masonry external walls with very large windows. Internally, it is divided into four bays by three rows of slender, cruciform-section, cast-iron columns, extending for eighteen bays on a north-south axis. Each bay measures about 10 feet (3 meters) square, and the average ceiling height is about 11 feet (3.4 meters). The columns support cast-iron beams spanned by the brick vaults that form the floor above.
The nearby warehouse and cross mill, also iron framed, were built soon after. In 1846 Professor Eaton Hodgkinson published Experimental Researches on the Strength … of Cast Iron, a definitive work that established a design methodology for cast-iron structures; together with Sir William Fairbairn he made a major contribution to the theory of nineteenth-century bridge construction. Cast iron is not fireproof; in fact, it fails structurally and rather dramatically at relatively low temperatures. Consequently, the designers of later iron-framed buildings found ways to protect the columns, often by encasing them in non-load-bearing masonry.
The Ditherington Flax Mill survives, reasonably intact. In 1886 the mill ceased operations, and the building was vacant for ten years. For another century, probably because it had large expanses of open floor space, it was converted to maltings for a brewery. It was empty again from 1987, when the brewery closed down, and has been quite badly vandalized since. In the mid-1990s proposals were put in hand for the refurbishment of all the buildings on the site, with the help of a grant from English Heritage. The project included the creation of shops, restaurants, a heritage information center, leisure facilities and offices, an art gallery, and some housing. In March 2000 Advantage West Midlands announced a £2.8 million (U.S.$4.1 million) grant for the restoration of the mill.