Page 259 - Masonry and Concrete

Masonry Veneer

258 CHAPTER SEVEN

designed, and arches may crack because of
LOAD
structural instability.
The most common method of support-
ing the masonry above openings is with
loose steel angle lintels. A length of steel
angle rests on the masonry on either side
of the opening but is not attached to the
backing wall. It should have a minimum
bearing length of 4 in. on each side of the
opening and be positioned so that it sup-
2
ports at least 3 of the masonry thickness.
Loose steel lintels allow the work to pro-
ceed quickly without the need for tempo-
1 /2 LOAD 1 /2 LOAD
REACTION REACTION rary shoring or a curing period. Cast stone
ARCH COMPRESSION and precast concrete lintels also provide
immediate support but require two work-
LOAD
ers or more for lifting the heavy sections
in place. Cast stone lintels are popular
because they add elegant detailing with
greater strength and lower cost than nat-
ural stone. A minimum end bearing of 8
in. is recommended for cast stone, rein-
forced concrete, and CMU lintels.
1 /2 LOAD 1 /2 LOAD
REACTION REACTION When masonry is laid in running bond,
LINTEL FLEXURAL TENSION it creates a natural, corbeled arch (Figure 7-
FIGURE 7-8 10). In fact, before true masonry arches
were invented, corbeled arches, vaults, and
ansfer in arches and lintels.
domes were used to span openings. Lintels
must be designed to carry the weight of the
masonry inside the triangle formed by the line of such arching action.
This triangular area has sides at 45° angles to the lintel, and its height is
therefore one-half the span length (Figure 7-11). Outside this area, the
weight of the masonry is assumed to be carried to the supporting abut-
ments by natural arching. For this assumption to be true, however, the
arching action must be stabilized by 8–16 in. of masonry above the top
of the triangle. If arching action cannot be assumed to occur because of
inadequate height above the load triangle, or because the masonry is not
laid in running bond, the lintel must be sized to carry the full weight of

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