For the strength and stability of walling the size of openings in walls is limited by regulations for both solid and cavity walls.
Jambs of openings
The jambs of openings for windows and doors in solid walls may be plain (square) or rebated.
Plain or square jambs are used for small section window or door frames of steel and also for larger section frames where the whole of the external face of frames is to be exposed externally. The bonding of brickwork at square jambs is the same as for stop ends and angles with a closer next to a header in alternate courses to complete the bond.
Window and door frames made of soft wood have to be painted for protection from rain, for if wood becomes saturated it swells and in time may decay. With some styles of architecture it is thought best to solid wail hide as much of the window frame as possible. So either as a partial protection against rain or for appearance sake, or for both reasons, the jambs of openings are rebated.
Figure 87 is a diagram of one rebated jamb on which the terms used are noted.
As one of the purposes of a rebated jamb is to protect the frame from rain the rebate faces into the building and the frame of the threshold window or door is fixed behind the rebate.
The thickness of brickwork that shows at the jamb of openings is described as the reveal. With rebated jambs there is an inner reveal and an outer reveal separated by the rebate.
The outer reveal is usually \ B wide for ease of bonding bricks and may be 1 B wide in thick solid walling. The width of the inner reveal is determined by the relative width of the outer reveal and wall thickness.
The depth of the rebate is either |B (about 51mm) or jB (102.5mm). A |B rebate is used to protect and mask solid wood frames and the \ B deep rebate to protect and mask the box frames to vertically sliding wood sash windows. The jB deep rebate virtually covers the external face of cased wood frames (see Volume 2) to the extent that a window opening appears to be glass with a narrow surround of wood.
Bonding of bricks at rebated jambs
Just as at an angle or quoin in brickwork, bricks specially cut have to be used to complete, or close, the \B overlap caused by bonding, so at jambs special closer bricks \B wide on face have to be used.
Provided that the outer reveal is \ B wide, the following basic rules will apply irrespective of the sort of bond used or the thickness of the wall. If the rebate is \ B deep the bonding at one jamb will be arranged as illustrated in Fig. 88. In every other course of bricks a header face and then a closer of \ B wide face must appear at the jamb or angle of the opening. To do this and at the same time to form the \ B deep rebate and to avoid vertical joints continuously up the wall, two cut bricks have to be used.
These are a bevelled bat (a ‘bat’ is any cut part of a brick), which is shaped as shown in Fig. 88, and a king closer, which is illustrated in Fig. 88. Neither of these bricks is made specially to the shape and size shown, but is cut from whole bricks on the site.
In the course above and below, two other cut bricks, called bevelled closers, should be used behind the stretcher brick. These two bricks are used so as to avoid a vertical joint. Figure 88 shows a view of a bevelled closer.
Where the rebate is 5B deep the bonding is less complicated. An arrangement of half bats as quoin header and two bevelled closers in alternate courses for English bond and half bats and king closers in alternate courses for Flemish bond is used.