In some localities it is the custom to form a ledge to support the floor joist by means of a continuous corbel of three or more courses. This is done to prevent weaking the wall by the ends of the floor timbers, for, of course, wherever wooden timbers are built into a wall they lessen the section or bearing area of the wall by just the amount of space taken up by the timbers, and in partition walls this is very considerable. The Chicago Building Ordinance provides that all walls of warehouses, 16 inches or less in thickness, and all walls of dwellings, 12 inches or less in thickness, shall have ledges 4 inches wide to support the floor joist, and in all cases where ledges are built they are to be carried to the top of the joist, as shown in Fig. 147. When walls are corbeled in this way it requires a plaster or wooden cornice, as shown by the dotted line, to give a proper finish for the angles of the rooms, and for this reason corbeling is not usually done where not required by law.
Corbeling for floor joist should not be attempted with soft or poor bricks.
The walls of a building should be carried up evenly, no part being allowed to be carried up more than 3 feet above the rest, except where it is stopped by an opening. Building one part of a wall up ahead of the rest produces unequal settlement, and, the joints in the higher part setting before the rest is added to it, the work laid last is apt to settle away from the other and weaken the wall, besides marring the appearance of it. Whenever it is necessary to carry one part of a wall higher than the rest the end of the high part should be •stepped or racked back, and not run up vertically, with only toothings left for connecting the rest of the work.
An important feature in the construction of brick buildings is the secure bonding of the front and rear walls to side or partition walls. When practicable both walls should be carried up together, so that each course of brick may be well bonded. If to avoid delay the side wall must be built up ahead of the front wall, the end of the side wall should be built with toothings, as shown in Fig. 148, eight or nine courses high, into which the backing of the front wall should be bonded. In addition to the brick bonding anchors made of 3/8x2-inch wrought iron,with one end turned up 2 inches and the other welded around a 5/8-inch round bar, should be built into the side wall about every 5 feet in height, as shown in the figure. The anchors should be of such length that the rod will be at least 8 inches in from the back of the front wall and extend at least 17 inches into the side wall. The building regulations of most of the larger cities require that all intersecting brick walls shall be tied together in this way.