Both ends of the joists will sink somewhat, on account of the shrinkage of the timber in seasoning, and the only way to make sure that the shrinkage at the two ends will be the same is to see that there is the same amount of horizontal timber at each end between the top of the floor and the solid masonry. This is be cause timber shrinks very much across the grain, but almost not at all along the grain. If the joists are framed properly into the sill, so that they are flush on the bottom with the sill, we have at the outer end of the joist a depth of horizontal timber equal to the depth of the joist itself, as shown in Fig. 13S; and in order to have the same depth of timber at the inside, the bottom of the joist must be flush with the bottom of the girder, which usually rests on brick piers. Of course the top of the girder must not in any case come above the top of the floor joists; therefore, in general, the girder must be equal in depth to the floor joists and flush with these joists on top and bottom, as shown in Fig. 150. This method is not always followed, however, in spite of its evident superiority; and the girder is often sunk several inches below the tops of the floor joists, as shown in Fig. 138, or even in some eases very much below, as shown in Fig. 151. Both of these methods cause an unsightly projection below the ceiling of the cellar. Where the joists are brought flush with the girder top and bottom, they may be framed into it with a and-tusk joint, as are the girders, as shown in Fig. 139, and a hole bored through the tenon to receive a pin to hold the joist in place.
Other methods of framing tenon-and-tusk joints are shown in Figs. 47, 4S, 49, and also a double-tenon joint in Fig. 50, which might be used in this case, although it is much inferior to the tenon-and tusk joint. Two joists framing into a girder from opposite sides should be fastened strongly together on top either by an iron strap passing over the top of the girder and secured to each joist, as shown in Fig. 152, or by means of a"dog" of round bar iron, which is bent at the ends and sharpened so that it may be driven down into the abutting ends of the joists, as shown in Fig. 153. These bars should be used at every fifth or sixth joist, to form a series of continuous lines across the building from sill to sill.
If the girder is sunk a little below the tops of the joists these may be gained into it in the same way as they are gained into the sill.
In this case joists should be arranged as shown in Fig. 154, so that they will not conflict with one another; and the two adjacent joists may be spiked together, thus giving additional stiffness to the floor. If the tenon-and-tusk connection is used, the joists may be arranged exactly opposite each other, provided that the girder is sufficiently wide, but it is always much better to arrange them as shown in Fig. 155, even in this case. The tenon may then be carried clear through the girder and fastened by a dowel as shown. Very rarely a simple
double-tenon joint, such as that shown in Fig. 50, might be used, but it is much inferior to either the gaining or the tenon-and-tusk joint. If the girder is sunk very much below the tops of the joists, as in Fig. 151, these will usually rest on top of it and be fastened by spikes only, or will be "sized down" upon it about 1 inch, as shown. There is no mortising of the girder in either case. Joists are also thus sized down upon the girts and partition caps, and are notched over the ledger boards as shown in Fig. 105. In cutting the joists for sizing and notching, the measurements should be taken in every case from the top of the joists, since they may not be all of exactly the same depth, and the tops must be all on a level after they are in place. This is really the only reason why the joists should be sized down at all, because otherwise they might simply rest upon the top of the girder, or girt, and be fastened by nailing.
With Brick Wall. When a joist or girder is supported at either end on a brick wall, there will either be a hole left in the wall to receive it, or the wall will be corbeled out to form a seat for the beam. If the beam enters the wall the end should be cut as shown in Fig. 156, so that in ease of the failure of the beam from overload ing or from fire, it may fall out without injuring the wall. Every fifth or sixth joist is held in place by an anchor, as shown in Fig. 157, of which there are several kinds on the market. Fig. 15S shows the result when a beam which is cut off square on the end, falls out of the wall.
There must always be left around the end of a beam which is in the wall, a sufficient space to allow for proper ventilation to prevent dry rot, and the end should always be well painted to keep out the moisture. Patent wall-hangers and box anchors arc often used to support the ends of joists in brick buildings, but only in case of heavy floors.
The floor framing in a brick building is the same as that in a building of wood except that there is no girt to receive the ends of the floor boards, so that a joist must be placed close against the inside of the wall all around the building to give a firm nailing for the flooring.