Fireproof buildings were constructed in Britain from the end of the 18th century following several serious fires in large timber-floored factories. Brick arch or slab floors were supported an iron beams and columns, between exterior load-bearing masonry walls. The causes of the collapse or partial collapse of 13 fireproof buildings are discussed, and the causes classified. Virtually all the collapses occurred during or shortly after construction, or in buildings which had suffered from lack of maintenance or had been damaged by fire. Most collapses started at the top, with the lower floors being unable to withstand the mass of material falling on them. 55 refs.