Opening Supports
Lintels and Arches
Relieving Arches
The brickwork over all openings may be supported, either by a steel or wood lintel, or by a brick arch. Either the full thickness of the wall or the face brick only may be carried on a steel lintel or an arch. Lintels are rarely used in combination with semi-circular arches. When a steel lintel or an arch supports the face brick, the backing usually rests on a wooden lintel, set higher than the arch or else concealed by the frame. There should be a brick relieving arch above wooden lintels, spanning more than 3 feet, bearing on the wall beyond the ends of the lintel, so that the brickwork will not be weakened should the lintel be destroyed by fire ([Fig. 28]). The space between arch and lintel is filled with brick after the arch is built. Seasoned brickwork will support itself over the smaller spans.
Steel Lintels
For a steel lintel over a small opening, an angle is sufficient. If the interior wall surface is also to be of face brick, the lintel is made by placing two angles back to back, as the usual wood lintel in such a place would be unsightly. For openings up to 4 feet wide, a 4" × 3" or a 3" × 3" angle is sufficient; wider openings up to 5 feet would require a 3" × 5" angle. Over larger openings heavier sections of steel have to be used. Both steel and wood lintels are usually made 8 inches longer than the width of the opening.
Brick Arches
The brick arches generally employed in small buildings are flat, segmental, or full semi-circular ([Figs. 25-29]). The segmental and semi-circular arches are usually best built of rowlock courses, their number depending upon the width of the opening. Flat brick arches over two feet wide should be supported by steel, the brick being usually set soldier fashion. As these brick are slightly inclined from the vertical, their end edges should be clipped to make the joints on the face of the arch come in a horizontal line, as in [Fig. 26]. In [Fig. 25], the appearance of the arch face is not so workmanlike and neat because the brick have not been clipped along the line of the middle joints. For either type of arch, the brickwork both sides of the opening must be beveled in the form of skewbacks, to serve as beds for receiving the thrust of the arch as shown in the figures. If these arches are properly handled both as to design and execution, they add greatly to the appearance of the entire wall surface.