Pieces of hoop iron are often laid flat in the bed joints of brickwork to increase its longitudinal tenacity and prevent cracks from unequal settlement. The ends of the iron should be turned down about 2 inches and inserted into the vertical joints. Nothing less than No. 18 iron should be used, and the holding power of the ties may be greatly improved by dipping in hot tar and then covering with sand. Hoop iron bond is strongly to be recommended for strengthening brick arches and the walls above, also the walls of towers, etc., and where an interior wall joins an external wall.
Although this belongs more especially in the carpenter work, it is mentioned here as a very important point in securing the stability of the wall and preventing its inclining outward.
Brick walls should be tied to every floor at least once in every 6 lineal feet, either by iron anchors, solidly built into the wall and spiked to the floor joist, or by means of a box anchor or joist hanger.
Fig. 141. - Cross Bond.
The forms of iron anchors most commonly used for this purpose are those shown in Fig. 142, the one shown at a being the most common, and about as good a style as any. The anchor shown at b answers equally as well, but costs a very little more. Anchors like a and b are spiked to the sides of the floor joist and built into the wall, as shown in Fig. 143.
If the wall is a side or rear wall, where the appearance is not of much consequence, it is better to have the anchor pass clear through the wall, with a plate on the outside, as such an anchor gets a much better hold on the wall than is possible when it is built into the middle of the wall. The cheapest form of anchor for this purpose is that shown at c, which has a thin plate of iron doweled and upset on the outer end. This style of anchor may also be used for building into the middle of the wall.
For anchoring the ends of girders, or where a particularly strong anchor is desired, the form shown at d is undoubtedly the best. This anchor is made from a ¾-inch bolt, flattened out for spiking to the joist and provided with a cast iron star washer. It possesses the advantage of having a nut on the outer end, which can be tightened up if desired after the wall is built. All of these anchors should be spiked to the side of the joist or girder, near the bottom, as shown in Fig. 143. The nearer the anchor is placed to the top of the joist, the greater will be the destructive effect on the wall by the falling of the joist, as shown in Fig. 143 A. For anchoring walls that are parallel to the joist the anchor must be spiked to the top of the joist, and should either be long enough to reach over two joist, or a piece of 1¼-inch board should be let into the top of three or four joist and the anchor spiked to it.
Any of these forms of anchors have the objection that in case the beams fall during a severe fire or from any other cause they are apt to pull the wall over with them. To overcome this objection, as well as to secure other advantages, the Duplex Wall Hanger, shown in Fig. 144, and the Goetz Box Anchor, shown in Fig. 145, have been invented These devices hold the timber by means of a rib or lug gained into its lower edge. The anchoring is not as efficient perhaps as is secured by the anchors shown in Fig. 142 but is ample for all ordinary conditions, especially as when these devices are used every joist is anchored.
These devices also offer the additional
Fig. Miadvantages that they do not weaken the wall, while they increase the bearing of the timbers and reduce the possibility of dry rot to a minimum. They also permit of easily replacing the joist after a fire.
Fig. 143 A.
The Duplex Wall Hanger is especially desirable for party and partition walls, as it obviates the necessity of building the beams intothe wall and permits the wall to be as solid at the floor levels as in other portions. (See Fig. 146.)
The importance of anchoring the joist to the walls, and thus pre-venting the walls from being thrown outward either from settlement in the foundation or from pressure exerted against the inside of the wall is very great, and should not be overlooked by the architect. Many walls have either fallen, or had to be rebuilt, that might have been saved by proper anchoring.