Jambs of openings and Rebated jambs - Walls.

Friday, February 4, 2011

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.

Rebated jambs.
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 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 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 1/2 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 1/4 B (about 51 mm) or 1/2 B (102.5mm). A 1/4 B rebate is used to protect and mask solid wood frames and the 1/2 B deep rebate to protect and mask the box frames to vertically sliding wood sash windows. The 1/2 B deep rebate virtually covers the external face of cased wood frames  to the extent that a window opening appears to be glass with a narrow surround of wood.

Fig. 87 Rebated jamb.

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