Masonry Magazine April 1982 Page. 17
Technical Notes
on Brick Construction
Brick Institute of America 1750 Old Meadow Road, McLean, Virginia 22102
36A
Revised
Sept/Oct
1981
BRICK MASONRY DETAILS
CAPS AND COPINGS, CORBELS AND RACKING
Abstract: Recommendations are provided for the development of successful details using brick masonry. Detailing of caps, copings, corbels and racking is specifically addressed. Performance, esthetic value and economics are the principal considerations in the development of successful details.
Key Words: bricks, caps, connections, construction, copings, corbels, design, detailing. economics, esthetic values, function, performance, racking, structural stability.
INTRODUCTION
This Technical Notes is the second in a series that discusses brick masonry details. This Technical Notes will address the detailing of caps, copings, corbels and racking. Technical Notes 36 Revised addresses the detailing of sills and soffits.
The recommended approach to detailing is covered in Technical Notes 36 Revised. While that Technical Notes is primarily for sills and soffits, it does provide the general approach applicable to all detailing. The following items should be considered in the development of a successful detail: 1. Functional considerations; 2. Esthetic value; 3. Construction considerations; 4. Economic considerations.
DEFINITIONS
Caps and Copings
The definitions for cap and coping are entirely dependent upon which dictionary or glossary is used as a reference. In addition, there are other terms which are used interchangeably with them, such as water table, canting strip, and offset. For the purpose of this Technical Notes, the word "coping" applies to the covering at the top of a wall, and the term "cap" refers to a covering within the height of the wall, normally where there is a change in wall thickness. The other terms cited will not be used.
Corbels and Racking
A corbel is defined as a shelf or ledge formed by projecting successive courses of masonry out from the face of the wall. Racking is defined as masonry in which successive courses are stepped back from the face of the wall.
CAPS AND COPINGS
# General
The primary function of caps and copings is to channel water away from the building. The cap or coping may be a single unit or multiple units. They may be of several different materials. The tops may slope in one direction or both directions. Additionally, where caps are discontinuous, a minimum slope from the ends of % in. (3 mm) in 12 in. (300 mm) should be provided, as shown in Figures 4 and 6 in Technical Notes 36 Revised.
The esthetic value the designer wishes to achieve may come from the configuration of the element, its color, or its texture. Caps and copings normally do not serve any structural function, and do not present any major problems in their construction.
# Materials
Caps and copings can be constructed of several materials: brick, pre-cast or cast-in-place concrete, stone, terra cotta, or metal. It should be pointed out that because of their location in the structure, caps and copings are exposed to climatic extremes. This severe exposure must be of prime concern to the designer. Because caps and copings are subjected to extreme exposure, brick masonry may not be the best choice of materials. This is because caps and copings of brick require more joints than do those made of other materials. This provides more avenues for possible water penetration into the wall. If brick is the material selected, great care must be taken to provide for the movement to which the element will be subjected and also to make sure all joints are properly filled with mortar. Concrete, stone and metal caps and copings can be installed in relatively long pieces, thus requiring less joints than do those made from brick.
Concrete, stone and terra cotta all have thermal expansion properties similar to those of brick masonry and normally present no extreme problems with differential movement when applied as caps and copings, if properly detailed. Metal has very different thermal expansion properties than brick masonry. Depending upon the metal used, its thermal expansion coefficient may be 3 to 4 times that of brick masonry. The designer should be aware of this and provide for this differential movement in the development of the details. Consid-
Sept/Oct 1981
Brick Institute of America
0000
4d
BRICK
MASONRY
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GENERAL DATA
DESIGN ELEMENTS