SYSTEMS/MASONRY
Mortar Joints
Given compatibility between the mortar and the masonry unit, the joint must be full and properly
tooled to control water leakage. Construction issues related to joint tooling are discussed below,
but the type of mortar joint is key at the design stage (see NCMA-TEK 85 and the PCA Concrete
Masonry Handbook). Figure 4.2.2 shows acceptable and unacceptable mortar joints for water
leakage control. Concave and vee joints are generally recommended when the joint is exposed to
rain. There is less consensus on beaded and weathered joints, with both reports of their providing
adequate performance and recommendations against their use. Therefore they are labelled as
marginally acceptable. Flush, raked, struck and extruded joints are not suitable unless
weather-tightness is not an issue, such as in interior construction. They should not be used on the
exterior face of the inner wythe of a cavity wall.
MARGINALLY
ACCEPTABLE
ACCEPTABLE
WEATHERED
BEADED
VEE
CONCAVE
UNACCEPTABLE
EXTRUDED
STRUCK
FLUSH
RAKED
Figure 4.2.2 Mortar Joints for Water Leakage Control
(Randall and Panarese)
Drainage and Flashing
Since it is practically impossible to make a watertight masonry wall, one must provide the means for
the drainage of water that penetrates the facade. This design feature is recognized in the design of
cavity walls, but drainage is also necessary in other masonry wall systems. Flashing is necessary
at a variety of locations to direct this water flow to the outdoors through weepholes or some other
such device. Good drainage requires the maintenance of an adequate space behind the facade,
through which water can easily flow downward. Construction technique is important for keeping the
cavity free from mortar droppings and installing the flashing such that it performs effectively, and
these are covered in the section on construction. Many of the design aspects of drainage, flashing
and weepholes are covered in available design guidance documents. Some of the key design
requirements are outlined below, based on material contained in BIA Technical Note No.21 B,
NCMA-TEK No.13A and the PCA Masonry Construction Handbook.
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