316. Under this heading it is proposed to describe some of the methods in use for shoring up buildings and for strutting and timbering excavations.

317. Fig. 95 shows the usual method of shoring up a building that is in danger of giving way, whether from defects in the structure, removal of the adjoining buildings, or excavations in the vicinity tending to affect the foundations.

Fig. 95.

A plank of timber 9 inches wide and 3 inches thick, the length varying with the height of the building, is placed against the upper part of the wall to be supported. In this plank rectangular holes are cut to admit of pieces of timber, called "needles," from 4 inches by 6 inches to 6 inches square and about 12 inches long. The needles are passed through the plank, leaving about 4 1/2 inches projecting on the outside, and penetrating about the same distance into the wall to prevent the plank from slipping, and on the outside to serve as an abutment for the ends of the struts A, A, A. These needles are shown at DD, Fig. 95. A cleat E is usually spiked to the plank on the upper side of each needle for additional strength.

The struts A, A, A, which are called "shores," are from 6 inches by 4 inches for very small buildings, to 12 inches by 9 inches for large buildings: half balks of timber, or about 12 inches by 6 inches, is a usual size. They are fixed at the lower end on a footing block F buried in the ground, and at the upper end against the under-side of the needles D, D. The outer strut is called the "top raker," and the inner one the "bottom shore," the other being called the "middle raker."

To retain the struts in their places pieces of timber, B, about 1 inch thick and from 6 inches to 9 inches wide, are usually nailed on each side of the struts at a short distance from or immediately under the points where the needles enter the plank. In furtherance of the same object, pieces of hoop-iron are nailed around the lower ends of the struts.

Sometimes, to save length, the top raker, instead of resting directly on the footing block F, is made to spring from the back of the strut immediately, under it at a distance of a few feet from the ground, a large cleat being spiked to the back of the strut to assist in supporting it. or a piece of timber is continued to the footing block for the same purpose.

318. In cases of houses where one in a row or terrace is taken down, and the party walls of those adjoining are not sufficiently strong to stand without support, struts are placed between the houses on the opposite sides of the opening, as represented by Fig. 96. D being a plank 9 inches wide and 3 inches thick, similar to that described in the last case, Fig 95, one of which is placed against each wall. Raking struts B, B, are fixed to the upper and lower ends of the plank against the wall, and to the horizontal strut A, which they stiffen The cleats E, E, and the straining piece C are for the purpose of keeping these raking struts in their places.

Fig. 96.

The horizontal strut A may be from 6 inches by 4 inches to 9 inches by 6 inches, and the raking struts B, B, about 6 inches by 4 inches, depending upon the height and distance apart of the buildings.

319 It frequently happens that the upper portion of the wall of a building has to be supported, while the lower portion is being removed, either wholly or partially, for the purpose of renewing the foundation, forming a doorway, or shop front, etc.

The method of shoring employed in such cases, though requiring extreme care on the part of the workmen, is very simple in principle. It consists merely in breaking one or more small openings through the wall, and inserting a beam or balk of timber in each of sufficient scantling to carry the wall above, and projecting at right angles on each side of the wall to admit of a stout prop being placed under each end. The props are made to rest on wedges to admit of the beam being wedged up tightly against the wall which it supports. The wedges are placed on stout foot-blocks of wood or stone solidly bedded in the ground. If the alterations be extensive, and are likely to be attended with risk, struts, as described in Art. 317, should also be applied to the building where required.