Compound shores are stiffened and braced either by rough boarding nailed across them or hound with bands of hoop iron (figs. i and 2). For further strength braces of 1-in. boards, 6 to 9 in. wide, are used to bind the shores and plate together. The wall-plate is usually a "deal" 9 in. wide by 2 in. thick, secured against the wall with wrought-iron wall hooks, forming a good abutment and serving to spread the pressure from the shores over a large area of the wall supported by them. Holes are cut through this plate to receive the needles, which are pieces of wood about I ft. long and 4 in. square in section, cut with a shoulder to butt against the wall-plate. A portion of a brick or stone is removed from the wall and the end of the needle is passed through the hole in the wall-plate into the recess in the wall. The head of the needle projects about 41 in. beyond the face of the wall-plate and forms an abutment for the notched head of the shore ; the notching prevents side movement. A cleat is housed and spiked above the needle to obtain a firm bearing.
Horizontal shores, or flying shores, may be employed for spans up to about 35 ft. They are used to support the party walls of buildings which adjoin premises being rebuilt. They are erected in stages during the pull ing down operations and removed as the new building is raised. A system of flying shores consists of one or more horizontal timbers, sometimes known as dog shores, cut in tightly between wall-plates similar to those employed in rak ing shores (fig. 3). These horizontal members are supported at each end by cleats and needles fixed in the wall-plate and the shores are supported in their length by inclined struts springing from needles fixed near the lower ends of the wall-plates and serving to strut the shore at a point about a third of its length from the wall. Corresponding braces are carried from the upper surface of the shore and abut against needles at the upper ends of the plates. Straining pieces are se cured to the upper and lower faces of the horizontal mem ber to serve as abutments for the ends of the struts. The best angle for these struts is about
but a smaller inclina tion has frequently to be adopted. Wedges are inserted, usually at the end of the flyer and sometimes between the struts and the straining piece, and gently driven to cause each tim ber to find a close bearing. If the adjoining premises are of considerable height and especially if it is proposed to undertake extensive excavations, the systems of flying shores may be com plicated, each consisting of several horizontal members spaced from so to 13 ft. apart, placed opposite floors or other solid masses
and well strutted one to another and to the wall-plate (fig. 4).
The members should be securely dogged and spiked together to form a rigid framework able to resist the attacks of a strong wind.
Horizontal shores are preferable to raking shores. Besides being more economical, they are more convenient and more efficient than rakers springing from the ground, especially if the height of the building is considerable and the span not much over 3o ft. They present a direct resistance to the thrust and are well out of the way of building operations that may be carried on below them, so that there is little risk of their being accidentally dis turbed ; raking shores may be disturbed by accident or loosened by digging and other operations.
is also known as vertical shoring or needle shor ing, and is adopted to support the upper portion of a building when necessary to reconstruct foundations or to make large open ings in the lower parts of the wall, as, for example, when put ting a shop front in an existing building. This form of shoring consists of horizontal members of balk timber or steel I-sections termed needles (very different from the needles used in raking and flying shoring), which are passed through holes in the wall to be supported, at a sufficient height to allow of the insertion of any arch or lintels that may be necessary above the proposed opening. The needles are supported at each end by an upright timber or dead shore, one on each side of the wall to each needle. These should not be allowed to rest upon any floor or vault but be carried down to a solid foundation and set upon and securely dogged to a timber sleeper running parallel to the wall. If it is not practicable to take the inner dead shore through inter vening floors down to the solid ground in one piece, and it is necessary for its base to rest upon the floor or upon sleepers placed on the floor, the shores must be continued in a direct line below it until a firm foundation is obtained. Between the needle and the head (or base) of the dead shores folding wedges are inserted to force the horizontal supporting balk firmly up to the underside of the masonry. Fixings between dead shores, needles and sleepers are made with wrought iron dogs. The spacing of dead shores depends upon the material of the wall ; for brickwork the intervals should not be greater than 6 ft. With this form of shoring it is often necessary to adopt supports auxiliary to the main shoring.