Page 404 - Construction Waterproofing Handbook

10.6 CHAPTER TEN
manufacturer. This eliminates unnecessary problems that prohibit envelope components
from acting cohesively together and preventing water infiltration.

Flashings
Because water is likely to pass through masonry facades, cavity wall construction with
dampproofing and flashing systems are necessary to redirect entering water.
Dampproofing materials, usually asphaltic or cementitious compounds, are applied to the
outer faces of interior wythes. This prevents minor amounts of water or moisture vapor
from entering interior spaces. Dampproofing requires flashing to divert accumulated water
and vapor back to the exterior through weep holes.
Envelopes often depend on flashing to maintain watertight integrity. Flashings are used
not only in brick masonry veneer structures but also in the following:
● Poured-in-place concrete
● Precast concrete panel construction
● Stucco or plaster veneer walls
● EIFS systems
● Stone veneers
● Curtain and window wall systems
Flashings are manufactured from a variety of materials, including noncorrosive metals
and synthetic rubber sheet goods. Metal flashings include copper, aluminum, stainless
steel, galvanized steel, zinc, and lead. Sheet-good flashings are usually a neoprene rubber
or a rubber derivative.
Thermal expansion and contraction that occurs in a facade also introduce movement
and stress into flashing systems. If installed flashing has no movement capability, it will
rupture or split, allowing water infiltration. Adequate provisions for thermal movement,
structural settlement, shear movement, and differential movement are provided with all
flashing systems (Fig. 10.5).
Flashing installed in cavity walls typically is the responsibility of masonry contractors,
who often do not realize the importance of properly installing flashings to ensure envelope
effectiveness. Common flashing installation problems include
● Seams not properly spliced or sealed (Fig. 10.6)
● Inside or outside corners not properly molded
● Flashing not meeting at building corners
● Flashing improperly adhered to substrates
● Flashing not properly shedding water
Besides these problems, masons often fill cavities with mortar droppings or allow mor-
tar on flashing surfaces. Additionally, weep holes are filled with mortar, damming water
from exiting.
These examples, and all problems associated with site construction, make it necessary
for all subcontractors to be made aware of their responsibility and of the interaction of all