FIREPROOF CONSTRUCTION. The sys tematic study of fireproof or fire-resisting build ing construction is a development of comparatively recent years. In 1900 fireproof construction was confined practically to buildings of pub lic or semi-public nature and to factories, stores, warehouses, and office buildings. and only the larger and more expensive of these structures were built with careful attention to the fire resisting qualities of their construction. The ex tension of fireproof construction to include all buildings is a development of the future. The earliest buildings having anything approaching a fireproof construction were those used for pub lic purposes, in the building of which the archi• tests were less hampered by considerations of economy in money and space than was neces saril• the ease in purely eruninercial structures. In these buildings the walls were made of suffi •ient thickness and stability to allow the use of vaulted floor construction, for wide]] brick arches were generally used, giving rise to much ex travagancy in space and dead weight. Partitions were generally brick walls and t he stairways were of stony or iron. The eat ire coast ruet ion was thus massive and heavy, and was, therefore. limited to buildings of small height and considerable area.
Modern fireproof construction began virtually with the use of iron in building construction. At. first attention was confined chiefly to the development of fireproof floor systems. Perhaps the first known example of iron and masonry fireproof flour construction was the cotton-mill of Phillips & Lee, of ;Manchester, England, erect ed in 1801. In this mill cast-iron floor-beams were spaced ten feet apart and brick arches were sprung between them. This construction, the vaulted floor construction previously men tioned, was very heavy, and no great progress could be expected in its extension to commercial and business buildings. In 1353 the rolled I-beam of wrought iron began to be made in Europe, and a yea later its manufacture was bt.gint in Amer ica. In 1885 steel I-beams began to be rolled in was used instead of the former plaster filling, to protect the bottom flanges of the 1-beams. With these innovations the flat-tile arch entered upon its final stage of development. About 1880 at• tention was turned to the design of colunm tection, but it was not until 1886 that such pro.
teetion was generally specified. Next to the hol America. With the rolled 1-beam it became possible to develop an I-beam and brick-arch floor system, in which the :lale* were reduced to such small space that a single thickness of bricks would make an arch of sufficient strength. This brought the weight of the floor down to 75 pounds per square foot. which was a decided im provement over the cast-iron floor-beam and low tile, the most commonly used materials for fireproofing are concrete and plaster compositions. The use of concrete for fireproof floors very pr0b• ably antedates the tile arch, but its active de velopment as a fireproof material has been vim brick-arch construction. The next attempt to improve upon fireproof floor construction was to spring curved sheets of corrugated iron between 1-beams and fill above them with concrete. This construction did not result in any material re duction in the weight of the floor, and it was further objectionable in that the arches them selves were not fireproof. Until 1370 the system of fireproof construction consisted of solid ma sonry walls inclosing a framework consisting of east-iron columns carrying a system of rolled iron floor-beams between which were sprung brick arches or arches of corrugated iron and con crete. The columns were left bare, as were the bottom flanges of the floo•-braces. To-day this is recognized as a faulty construction, but in the early days of the art of fireproofing iron, being incombustible, was also regarded as fireproof.
The next development in the construction of fireproof floor systems was the invention of the hollow tile, 'flat' arch, which was first applied in the Kendall Building in Chicago in 1872. About the same time a similar but heavier con struction was used in the New York Post-Office. For the next ten years the development in tile arches consisted of attempts to design a lighter construction and at the same time to obtain a stronger construction. Until about 1333 all tile arches projected about one-half inch below the bottoms of the floo•-braces, and the incased spaces thus left under the beam flanges were filled with plaster. All tiles were also made without interior webs.