Varieties Of Floors. The most striking, and indeed the only variety of floor which comes under our notice here, is what is known as the "fire-proof floor," of which there are several kinds now to be briefly noticed. The principle of a fire-proof floor may be briefly stated. Wood, of which ordinary floors are constructed, being highly inflammable, it must either be combined with other material not easily, or altogether, incapable of being consumed by fire; or the timber may be altogether dispensed with, and the floor made wholly of incombustible material. The incombustible materials hitherto employed have been mortar, plaster of Paris, and various kinds of concrete, these being supported by either a combination of timber, or of iron and timber together, or of iron wholly. The oldest combination forming a fire-proof

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Fig. 204.

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Fig. 205.

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Fig. 205a.

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Fig. 206.

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Fig. 207.

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Fig. 208.

The floor may be made fire-proof if concrete, as described in connection with fig. 205. In fig. 208 we give side elevation of this floor. In figs. 209 to 213 we borrow from the "Engineer" illustrations and the preceding paragraphs, a description of a simple modification of the above.

"The system illustrated by the accompanying drawing has been adopted in Paris for a house of cheap construction, its advantages being that it does not require any forged work, such as braces or cramps, nothing but the joists and iron cut in lengths, so that it is applicable in situations where special workmen are not available.

" In the case illustrated the joists of double T iron are 32 inches apart, from area to area, every other one being anchored in the walls; the iron laths, or lattice work, being composed of 2/5 inch square iron, and resting on the lower shore of the joists. The laths are nearly 32 inches in length, and rather less than 7 inches distant from each other, and are slightly curved, as shown in fig. 210, thus leaving a space beneath of about half an inch in the centre for the parget work.

" The end laths are nearly 44 inches long, curved like the others, the end being bent down to the extent of 2 inches to form a cramp, as shown in fig. 211.

SCALE 15 IN 1000

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Fig. 209,

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Fig. 210.

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Fig. 211.

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Fig. 212.

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Fig. 213.

" The plaster pugging is placed upon the laths up to the height of the joist at the sides, but not more than 4 inches thick in the centre.

" The floor represented in the engraving measures 26 feet by 16 feet 3 inches, and its total weight is under one ton, or about fifty pounds to the square yard; the total cost of the iron work was under 14. This gives the new system the advantages over that in common of sixty pounds less weight, and 16 shillings in cost, or 5 per cent.

"The advantages claimed for this method are that it presents great resistance, while the superincumbent weight is better distributed than usual on account of the proximity of the laths to each other. In cases, however, where larger materials have to be used the laths may be set eight or ten inches apart, and under these circumstances the economy would be increased to about 10 per cent. The main point is, however, that all the iron work may be ordered of the required lengths, so that any ordinary workman can put it together."

A system extensively used in this country for forming fireproof floors is that known as " Fox and Barret's " from the names of the patentees who introduced it to notice. This is illustrated in cross section in fig. 214, and in side elevation in fig. 215; and is made up of wrought-iron rolled beams a a, resting at their ends upon the walls. These support on their lower flanges or shores the wood battens b b, upon which rests the mortar c c. On the upper surface of this a layer of concrete, as d d rests, in which rests the wood boards e e, these being nailed in fillets //, embedded in the concrete d d. In fig. 216 we give the cross section of the form of fire-proof floor introduced by the Messrs. Burnett of Deptford, in which the concrete floor surface - a floor formed as in the illustration already given - is supported upon hollow brick, or upon bricks made light by being punched with apertures as shown, these are placed together so as to form an arch with a gentle rise; the outside ones resting upon or butting against cast-iron boxes b b, and the whole being further secured by the wrought-iron tie rod c c. The arches of hollow bricks a a, may carry wrought-iron bars d d, upon which rests the concrete e e, f being the battens.

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Fig. 214.

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Fig. 215.

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