[Sidenote: Lintels and Arches]
[Sidenote: 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.
[Sidenote: 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.
[Sidenote: 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.