Page 423 - Construction Waterproofing Handbook

THE BUILDING ENVELOPE: PUTTING IT ALL TOGETHER 10.25
placed into a substrate for crack control, such as recessed control joints. These control
joints are later sealed or provided for aesthetic purposes, as in precast panel construction.

Waterstops
Waterstops, although limited to concrete construction, are highly effective for transitions
between separate concrete pours (referred to as cold joints) and terminations between ver-
tical and horizontal concrete placements. Waterstops are now produced in a variety of
designs and materials, including extruded rubber and hydros clay materials.
Remedial waterstop applications are now available. Cold joints with or without failed
waterstops are chipped or sawn out along cracked areas. Manufactured tubing is then
placed into this chipped-out area, and the joint is packed with nonshrink grout and cured.
Then a urethane grout material is pumped into the tubing and filled, forcing expansion of
the tubing and effectively sealing the joint.
Waterstops are effective in preventing lateral movement of water at cold joint areas.
These joints are subject to cracking due to concrete shrinkage, and allow water penetration
if a barrier such as a waterstop is not installed.
Waterstop materials are manufactured with flanges that allow each side of a joint to be
securely anchored to the concrete. A common problem with waterstop usage is that water-
stops are frequently installed by concrete finishers who do not understand their importance
and effect on a building envelope.
Waterstops often end up bent over, cut, or not lapped properly at seams. They are even
completely removed during concrete placement because they get in the way of the concrete
finishing process. Waterstop installations must be carefully inspected by construction man-
agement personnel during concrete placement operations, to ensure that such activities do
not occur. Waterstops are covered in detail in Chap. 2.

Other Transition Systems
A variety of other transition materials and systems frequently are used in construction
practices to provide complete waterproofing of the building envelope. Among these are:

● Pitch pans
● Thresholds
● Integral flashings of curtain and window wall systems
● Expansion joint systems
● Cants

All of these systems ensure envelope watertightness by providing a transition or termi-
nation between dissimilar materials. They also allow for differential movement between
various waterproofing systems, or allow entering water to be redirected to the exterior.
For instance, thresholds placed under doorways prevent rain and wind from entering
interior spaces. They also provide a watertight transition among the exterior surface, door-
way, and interior areas. Pitch pans provide a watertight transition among mechanical
equipment supports, roofing, and structural roofing components.