Masonry Magazine March 1971 Page. 33
NCMA-TEK
An Information series from National Concrete Masonry Association
Concrete Masonry Lintels
25
General
Lintels are horizontal members spanning openings in walls. They function as beams in supporting the weight of the wall and other loads over the openings, and transmit these loads to the adjacent masonry. They may be of reinforced concrete masonry construction, of precast or cast-in-place concrete, or of structural steel. Cast-in-place lintels have the disadvantage of possessing shrinkage characteristics and surface textures which are not compatible with adjoining masonry.
Reinforced concrete masonry lintels are made up of specially formed lintel masonry units, of bond beam masonry units or of standard units with depressed, cut out, or grooved webs. The units are laid end to end to form a channel in which reinforcing steel, and concrete or grout are placed. They are easy to construct and in addition do not require any special hoisting equipment. Also the bond pattern and the surface texture matching that of the surrounding masonry may be maintained. Masonry lintels may also be prefabricated prior to installation in the wall, and then installed as a precast lintel. Typical sections for masonry lintels are shown in Figure 1: reinforcing details are shown in Figure 2.
Precast lintels are advantageous in some respects as they are delivered ready for use, do not require shoring, and can carry load as soon as they are in place. These lintels can be produced with a surface texture closely matching that of masonry units, and can be scored vertically to simulate mortar joints 16 inches on center. Precast lintels may be one-piece or split (two thinner sections). Split lintels are relatively light in weight, easy to handle and the air space between the sections provides some added insulation value. Split lintels are not recommended to support combined wall and floor loads because of the difficulty in designing the heavier-loaded inner section to have the same deflection as the outer section which may be carrying wall load only. Differences in deflection of the two sections could result in undesirable stress concentrations in the masonry wall.
FIGURE 1. Concrete Masonry Lintel Sections
A. For metal or wood sash installed after wall is erected. These units make an efficient and weathertight joint.
B. For metal sash only installed as wall is erected.
C. For finished masonry openings where no windows or doors occur. These units may be employed to form continuous lintel and bond beam course.
KNOCKOUT
BOND BEAM
BOND BEAM
BOND BEAM
DOUBLE CORE
Concrete Units
TEK 25 1971 National Concrete Masonry Association