Framed And Double Floors. In this kind of floor there is an additional member called a " binder," or " binding joist," as 6 6 in fig. 197, a a being the "flooring joists," c the "ceiling joists," and dd the "flooring boards." The thickness of the binding joist varies with the bearing; as a rule, they are made half as thick again as the flooring joists of the corresponding floor; the bearing on the wall will be ample if at six inches. The distance between the binders, measured from centre to centre, is generally from five to six feet.
12. "Double Framed Floors" - Floors have an additional member, this being called a " girder," or sometimes simply a " bearer." Floors of this kind are used with large bearings, or where heavy weights have to be supported; a a, fig. 198, the "girder," ee the "binding joists," f f the "flooring joists," h h the "ceiling joists." The ends of the "girder" are carried by the walls, and are, or should be, placed in the parts where there is no opening, as that of a window or door, below; that is, on the part of the wall which is solid from bearing of girder to the ground or footing. And in order to allow of the pressure on the wall being distributed as much as possible, the girder a a a, fig. 199, rests upon a "plate," or "template" b b, which will be better if of stone than of wood. This plate should have a considerable projection on each side of the bearer; a stone cap cc, and backpiece d, are usually added, thus enclosing the end of the girder a a in an open box, so to call it, thus freely exposing the timber to the air. Girders are sometimes placed in castiron boxes, called " girder boxes," as a a, fig. 200, or as in fig. 201, which is a form sometimes used where a "set off" occurs, that is, where the thickness of the wall a a is reduced to that at b b. The box c c is sometimes secured to the wall by a screw-bolt and nut, as d d, passing through a bearing plate e e, which having a wider bearing, tends to strengthen the opposite walls. Where cast-iron or wrought-iron beams are used as girders, as in fig. 202, the wood-binding joist bearer rests either upon the upper flange, as at a, or upon the lower flange of the beam, as at b, or upon a projecting part c, to which the beam d is bolted. The first of these two methods is the strongest. In place of inserting the ends of "girders" into apertures in the walls, as illustrated, or into cast-iron boxes, they are sometimes made to rest at, or bear upon the upper surfaces of stone corbels, as at a, fig. 203, or on cast-iron boxes or brackets as at b, which project from the wall, thus keeping them free from it, and quite exposed to the air. The girder a a, fig. 198, carries the "binding joists" e e, which are framed, or jointed, to the sides of the girders, and the "binding joists" e e, carry the "flooring, or bridging joists "f f , upon which the "flooring boards " g g, are placed. The "ceiling joists" h h, are carried by the binders, and to these are secured the laths and plaster ceiling. The
floor, and which is yet in some places still used, is that illustrated in figs. 205 and 205a, which is taken from our article in "The Field," alluded to in the vol. on Brickwork and Masonry, when treating of Concrete Construction generally. In this, a a are the joists, to the under and upper edge of which fillets or battens of wood are nailed, the upper edges being placed at a distance of two or three inches from the upper surface of joist. On these fillets are placed laths c c, on which is laid the mortar d d. In this, while soft, the battens e e are imbedded, these carrying the flooring-board f f, or if concrete be used, then the battening and boards may be dispensed with, and the floor surface formed with concrete alone. The ceiling may be formed in the ordinary way, but to make it fire-proof, fillets, as g g, may be nailed across the lower sides of the joists a a, and mortar or concrete h h forced between the interstices which may be left an inch wide. The surface below the fillets, as g g, being either left plain as at i, or corrugated as at i, this last being done by means of a boarded platform placed beneath the fillets g g, while the concrete or mortar is being forced between the fillets g g. The drawing, fig. 205a, shows a cross section at upper, and, fig. 205, plan at lower, parts. A fire-proof floor and ceiling may be formed, as in fig. 206, by a series of small arches, these being formed by the timber moulds b b placed between the joists a a, and resting upon fillets c c, nailed to the inside of the joists, which may be removed when the concrete filling up, as at e e, is set. The ceiling being finished in the usual way, or as illustrated and described in connection with last figure given. Fig. 207 illustrates, on side elevation, a floor formed by a combination of iron with timber and concrete, which is much used abroad. Wrought-iron rolled beams a a are placed so as to rest at their ends upon the walls, being placed about thirty to thirty-two inches apart, these beams carry saddles b b of wrought or cast iron, which again carry wrought-iron laths c c, and on the upper surface of which rests square iron bars d d, and above the whole the concrete e e. The floor is formed by wood-battens f f resting upon, and notched into, the upper flange of the beam a a, the flooring joists g g resting upon the battens.
Fig. 20a distance apart of the "girders," a a, fig. 198, is usually ten feet from centre to centre, the bearing on the wall nine to twelve inches. Floors are, in the better class of floors, provided with what is called " deadening" or "deafening." This is made as follows: - To the sides of the flooring joists f f, fig. 204, small "fillets," or "firring pieces," k k, are inserted, which carry the "sounding boards" 11, on which is laid the " pugging," made of coarse plaster or mortar.