FIRE-RESISTING FLOORS.

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FIRE-RESISTING FLOORS.

(Specially written for FIRE AND WATER.) (Concluded.)

ONE very modern type of fire-resisting floor makes use of triangular lintels, which pass from joist to joist and rest on the lower flange, whose under surface they cover. The older type is shown in figs. 14, 15, while the newer is illustrated in fig. 18.

Figs. 16, 17, and 18 show a combination of lintels, all flat, of T section, and corrugated iron permanent centering. Fig. 19 is a floor of solid concrete, with terra cotta casings to flanges —a form of floor which of course, calls for temporary centering. The concrete is absent in fig. 16, but is shown in fig. 18.

FIG. 13.FIG. 14.

In fig. 20 clay shields protect the lower flanges of the joists and support a corrugated permanent centering for the concrete—there bring besides a suspended ceiling of wire lathing and plaster.

FIG. 15.

In figs. 21. 22, and 28 concrete blocks of adamant or other equally fire-resisting cement, with breeze or other aggregate, form the lintels, which are also somewhat reinforced by the insertion of steel laths. A concrete filling is laid on these lintels, which vary slightly in form, ns will be seen from the accompanying illustrations.

FIG. 16. FIG. 16.FIG. 17.

Other floors, as in fig. 24, are made of loose fireclay bricks which inclose the flanges of the joists and form corbels, on which the hollow fireclay lintels rest— these serving as the permanent centering for a slight finish of concrete. Others, again, as in figs. 25, 26, consist of two hollow tubes between each pair of joists, with a concrete filling-in, limited in amour aud forming the key between the tubes, or a systei of cellular tubes between the joists is adopted, who* special feature is the use of gypsum lintels or cellule tubes.

FIG. 18.

In the case of domestic buildings and those in whic the floors are not intended to carry any great weight or are of small spans, concrete slabs, with expanded metal or other lathing or iron rods may be employed. Some architects and builders make use of wood beams set diagonally in such a way as to act as skewbacks, in which are set concrete slabs or arches of the same material.

FIG 19.

Sometimes also a flat floor or (more frequently) one which is arched in section, consists of plain roofing tiles, and in three or four courses laid in cement, and breaking joint with or without a finish of fine concrete on top. This method, however, is out of date, and was chiefly used for corridors and other situations where the span of the floors is inconsiderable.

FiG. 20.FIG. 21.

In England other and cheaper forms of “fire-resisting” floors are often employed. Some are constructed of ordinary wooden joists nailed together—and this practically forming a solid floor; or the space between the floor joists of the common and usual class is blocked in solid with wood at the lower part of the joints, to which is occasionally added a layer of concrete. “Pugging” on fibrous plaster slabs sometimes or laid on metal lathing without rough boarding and nailed to the underside of the wood joists is not uncommon, or the cellular gypsum slabs already alluded to protect the underside of an ordinary woodenjoisted floor,for which purpose also areemployed various combinations of special fli’e-resisting plasters, such as asbestos, fibrous, or silicate cotton plaster, adamant, and other cements, and special lathings, such as the expanded metal already referred to or flat ribbons interlaced in lattice fashion and inserted between their interlacing. One class of metal lathing (“Thimil”) consists of flat sheets of metal cut, and bent up and down to form projecting stripes, w’hereby is left space for keying. In another style woven iron wire is studded with terra cotta at its intersections.

FIG. 22.FIG. 23.FIG. 24.

Of^the concretes specially intended to resist fir more thoroughly than the ordinary concrete are gypsum concrete and one in which Kieselgulir (into which silicate enters extensively) is very commonly employed.

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FIRE-RESISTING FLOORS.

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FIRE-RESISTING FLOORS.

(Specially written for FIRE AND WATER.)

FIRE-RESISTING floors—(that phrase is used in preference to fireproof)—form one of the principal features in a modern “fireproof” building, and new materials and new combinations therefor are constantly being devised. Whether or not the ideal floor has yet been discovered—one which will withstand the onslaught of both fire and water, singly and combined—is the question. Mere non-combustibility is by no means everything; there are other points to be taken into consideration. For instance, such floors must not be liable to melt; they must not be susceptible of warping, distortion, or breakage either under fire or when water is thrown upon them while a fierce fire is raging; and they must resist the influences of the greatest possible extremes of heat or cold in the line of expansion or contraction. Hence floors of metal work are ruled out, and whatever structural metal work is in the neighborhood of the floors must be sheathed wftli some material which is non-conductive of heat.

FIG. 1.Fin. 2.

Hence, it is obvious that girders of cast iron, or joists of rolled iron or steel, supporting brick arches, must also be ruled out, even though wrought iron tierods are inserted, so as to avoid trouble from the thrust of the arches. If iron could be dispensed with altogether in such structures, the possibilities and probabilities of arriving at a solution of tfie problem of how to obtain fire-resisting floors would be much nearer completion. As it is, there are nowadays no fire-resisting floors which do not protect the iron work, somehow or another, if only by a suspended ceiling.

FIG. 3.

Many fire-resisting floors are found, especially in England, where the centering is permanent. These are built with sheets of galvanized iron, corrugated and curved, which rest upon the upper surfaces of the lower flanges of the iron joists. Above this centering is a concrete filling-in. In some cases, the expanded metal lathing is embedded in the lower part of a concrete slab, thereby imparting that tensile strength which is lacking in simple concrete. Sometimes this arrangement is above the joists (as in figure 1)—the latter being themselves embedded in concrete, which, in its turn, is cased round with metal lathing, and is either plastered or protected by a BUB pended ceiling. Sometimes the reverse process is adopted, and the joists are embedded in the concrete slab (as in figure 2) with the metal lathing placed between the joists or below them (as in figure 4). Occasionally also (as in figure 3), arched ribs of “channel ’’ iron (an iron bar or beam having a. section resembling a flat gutter cr channel) and concrete provide additional strength for the slab of concrete. In some cases, a suspended ceiling is present; in others, not. In the example of the hanging arrangement for the suspended ceiling, the wire lathing is attached to the thin bars bj” the clips (as shown in figure 5 with the joist cased).

FIG. 4.no 5.

In some floors flat arches are used between the joists—the under side of the joists, on which the arches rest, being carefully protected. Such arches may be built in fire-clay blocks, the sinkings on the sides being dove-tailed, so as to form a key for the cement, (as in figure G); or perforated blocks, tied together with iron rods passing through the joists (as in figure 7; are employed, or solid fire-clay blocks iriclosing the lower part of the joists and formingthe skewbackof the arches. As to the material of which the hollow bricks are made: Oneof the most common is a mixture of clay with sawdust before burning. This forms a very light and porous brick. Fig. 6 shows a fireproof floor where the steel joists, except* ing the under side of thelower flanges, are altogether embedded in the concrete—these flanges being protected by the suspended ceiling hung from the top of the steel joist. In this figure the floor is shown with the wood centering in position, for whose removal the ceiling-hangers are hinged.

FIF. GFIG. 7.FIG. 8.

Fig. 7 shows the iron work wholly embedded in solid “pumice” concrete, whose constituents are cokebreeze, sand, and Portland cement. In this style interlaced tension rods pass over and under the joists.

FIG. 9.

In fig. 8 the floor is of steel decking, above which is a “ pumice” concrete filling-in. The under surface of the lower flanges of the joists and that of the steel decking have no protection—that is supplied by a suspended ceiling, as is shown in the cut. Such a floor is designed with a view to its capabilities in sustaining a heavy load.

In the case of floors whose const ruction is independent of any temporary centering (figure 8), or where a permanent centering is supplied, and where the joists are completely protected, the lintel, rather than the arcuate principle of construction is adopted (fig. 9) Of such floors there are several types. In one (fig. 10) the arrangement of the hollow tubular earthenware lintels, which form the centering for the concrete filling above, as shown in cut, is diagonal, each diagonal being at right angles to the joist-line. In this way, the lintel forms a more complete covering to the under side of the lower flange of the joist. In another style of floor, each lintel has two tubes, with projections at the side for interlocking purposes. (See figs. 11 and 12.)

FIG. 10.FIG. 11.

Fig. 12 shows an arrangement of flat terra cotta slabs, with grooved edges, fitted to the flanges of small T iron bearers, spanning the distance between the joists. Thelower flanges of the joists an covered with blocks, specially made, whereby is formed a complete permanent centering for the concrete.

FIG. 12.

(To be continued).

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