Masonry Magazine April 1982 Page. 18
The selection of materials for caps and copings is dependent on the architectural requirements of the structure. Consideration must also be given to the drying shrinkage of the element if cast-in-place concrete is the material selected.
If brick is the material chosen for the coping, it may be desireable in some applications to use a special shape to get a positive slope in two directions. In most applications, the slope should be only in one direction, with drainage onto the roof and not down the wall face. In such case, the coping can be built using regular shapes.
Design
The prime consideration in the design of caps and copings is the performance of the element in service. The designer must take into consideration the movement of the element, differential movement between the element and the wall, joint configuration and material, connection of the element to the wall, and type and location of flashings.
The esthetic value of the detail should be evaluated. As with details of other elements, selection of material, color, texture and configuration will effect the esthetic value of the detail. The designer has a wide range from which to choose, but he must keep in mind that the performance should not be compromised to achieve esthetic value.
The economic considerations are seldom a major consideration in the development of details for caps and copings. The material selected may have a minor effect on the economics of the detail. It affects the economics not only by its own costs, but also by the economics of installation. The economic considerations should not have a deleterious effect on the performance of the detail in service.
Details
General. The function of caps and copings is to prevent the entry of water into the wall where the wall becomes partially or totally discontinuous vertically. Caps should have the top surface sloping downward, away from the face of the wall above. Copings may slope in one or both directions. In all cases, the slope should be a minimum of 15 deg from horizontal.
The caps should overhang the wall face on the exposed side. Copings should overhang the wall on both sides. The overhang should be of sufficient dimension so that the inner lip of the drip is at least 1 in. (25 mm) from the face of the wall. Since the function of caps and copings is to prevent moisture penetration, the fewer the number of joints, the more assurance that the detail will perform its function.
Flashing and Weepholes. Flashings for caps and copings generally serve a different function from flashings used elsewhere in the structure. Flashing used with caps and copings has as its prime function the prevention of the entry of moisture into the wall. The collection and diversion of the water from the wall becomes a secondary, although important function.
PRECAST CONCRETE
OR STONE COPING
SEALANT AND
BACKING ROD
FLASHING
METAL
TIES
AIRSPACE
DOVETAIL
TIES
DOVETAIL SLOT
1 IN. (25 mm) MIN
DOVETAIL TIES
REINFORCEMENT,
BOTH HORIZONTAL
AND VERTICAL
SOLIDLY FILLED
WITH GROUT
FLASHING AND
COUNTER-FLASHING
RIGID
INSULATION
Precast Concrete or Stone Coping on Cavity Wall Parapet
FIG. 1
In order to properly anchor caps and copings to the wall, it may become necessary to penetrate the flashing with the anchor, see Figs. 1. 3. and 4. To prevent moisture from entering the wall, at these points, it is absolutely necessary that the penetrations be adequately sealed, or the flashing will fail to function as intended.
Flashings should be extended beyond the face of the wall and bent downward ¼ in. (6 mm) to form a drip, as shown in Figs. 2, 5, and 6. Metal copings may also serve as flashings. It should be recognized that exterior flashings not contained within the wall serve the same functions as do interior flashing. Information on flashing materials is provided in Technical Notes 7A.
METAL
SNAP-ON
COPING
MASONRY
NAIL
SEALANT
METAL
TIE
DOVETAIL
TIE
Coping for Cavity Wall Parapet
FIG. 2
MASONRY
NAIL
SEALANT
RIGID
INSULATION
2