Page 162 - Masonry and Concrete

Masonry Construction Techniques
161
MASONRY CONSTRUCTION TECHNIQUES

weather resistant. Other, more specialized effects can be achieved with
tools to bead or groove a mortar joint. The most moisture-resistant
joints are tooled concave and V-shaped joints. Mortar squeezes out of
the joints as the masonry units are set in place, and the excess is struck
off with a trowel. After the mortar has become “thumbprint” hard (i.e.,
when a clear thumbprint can be impressed and the cement paste does
not stick to the thumb), joints are finished with a jointing tool slightly
wider than the joint itself. As the mortar hardens, it has a tendency to
shrink slightly and separate from the edge of the masonry unit. Proper
tooling compresses the mortar against the unit and compacts the sur-
face, making it more dense and more resistant to moisture penetration.
Concave or V-tooled joints are recommended for use in areas subject to
heavy rains and high winds. However, full head and bed joints and
good mortar bond are more critical to moisture resistance than tooling.
Less moisture-resistant joint treatments may be used in mild to moder-
ate exposures if the workmanship is good, the bond between units and
mortar is complete and intimate, and the flashing and weeps are prop-
erly designed and installed.
Horizontal joints should be tooled before vertical joints, using a
long jointer sometimes called a slicker that is upturned on one end to

CONCAVE* RAKED V–JOINT* BEADED STRUCK

* MOST
MOISTURE
RESISTANT

WEATHERED FLUSH SQUEEZED, GRAPEVINE
EXTRUDED,
OR WEEPING
FIGURE 5-23

Masonry joint profiles.

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