Page 400 - Construction Waterproofing Handbook

10.2 CHAPTER TEN
To offset this situation, brick joints should be expertly crafted, including properly mix-
ing mortar, using full bed joints and proper tooling of joints, Joint toolers compress mor-
tar against both sides of attached brick, compacting the material, which assists in
preventing water from passing directly through joints.
Water that passes through joints carries salts extracted from cement content in mortar.
The whitish film often occurring on exposed masonry walls is referred to as efflorescence.
It is formed by salt crystallization after water carrying the salts is drawn by the sun to the
surface. This water then evaporates, leaving behind the salt film.
When salts crystallize within masonry pores, the process is called cryptoflorescence.
Formation of these crystals can entrap moisture into masonry pores that cause spalling dur-
ing freeze–thaw cycles. Additionally, if cryptoflorescence is severe enough, it will prevent
the natural breathing properties of a masonry wall. Both forms of salt can attack and cor-
rode reinforcing and supporting steel, including shelf angles. This corrosion often leads to
structural damage.
An effective joint tooling method is a weathered joint finishing. In this tooling installa-
tion, a diagonal is formed with mortar, with the recess at top, allowing it to shed water.
Recessed joints, including struck and raked joints, can accumulate water on horizontal por-
tions of the recess and exposed brick lip. This water may find its way into a structure
through mortar cracks and voids. Commonly used joint types appear in Fig. 10.1. All
masonry mortar joints as well as all building envelope components should be designed to
shed water as quickly as possible. Figures 10.2, 10.3, and 10.4 provide proper sloping
details of envelope components.
Once major envelope components are selected and designed, transition systems are cho-
sen to detail junctures and terminations of the major components. Transition materials and
systems ensure the watertight integrity of an envelope where changes in facade compo-
nents occur, or at terminations of these components.

TRANSITION MATERIALS

There are two basic cladding details for above-grade envelope facades used to prevent
water infiltration. The first type is a solid, single-barrier wall system with no backups or
secondary means of protection (e.g., single-wythe block walls, stucco over metal lath, and
exterior insulated finish systems). The second type is a multicomponent system, or diver-
tor system, providing at least two waterproofing methods. These include the cladding
itself, and backup systems consisting of flashing and weeps that redirect water passing
through first-line barriers (e.g., brick cavity wall, metal and glass curtain walls with inte-
gral gutters, flashing, and weeps).
Multicomponent systems often provide better resistance to water infiltration by providing
systems that redirect water bypassing the initial barrier back out to the exterior (e.g., EIFS sys-
tems with drainage capability). These systems are most effective when this redirecting is chan-
neled immediately out to the exterior and not allowed to drain into other interior systems. The
latter allows an envelope to become susceptible to leakage into interior areas.
As previously emphasized, however, it is typically not the primary waterproofing bar-
riers themselves that directly cause water leakage, but rather the transitions between these