Page 49 - Construction Waterproofing Handbook

BELOW-GRADE WATERPROOFING 2.13
Waterstops are premanufactured joint fillers of numerous types, sizes, and shapes.
Waterstops are available in a variety of compositions including
● Polyvinyl chloride (PVC)
● Neoprene rubber
● Thermoplastic rubber
● Hydrophilic (modified chlorophene)
● Bentonite clay
● Asphalt plastic

The first three, PVC and rubber types, are manufactured exclusively for use in poured-
in-placed concrete structural elements. The remaining three, while mainly used for con-
crete installations, can be used with other building materials such as concrete block and
are also excellent where installations involve metal protrusions in or adjacent to the con-
struction joint. Manufacturers also make waterstops that are resistant to chemicals and
adverse groundwater conditions. A summary of the properties of the various type water-
stop is shown in Table 2.1. As with many products, manufacturers have begun making
systems that approach “idiot-proof” installations.
PVC waterstops have long been the standard within the construction industry. They are
provided in a variety of shapes and sizes for every situation to be encountered, as shown
in Fig. 2.16.
PVC waterstops with the dumbbell shape in the middle are used for installation where
actual movement is expected in the substrate, typically not thermal movement but structural
movement. Figure 2.17 shows an expansion joint installation with the bulb portion of the
waterstop left exposed to permit movement. However, waterproofing applications require
the joint to be filled with a properly designed sealant joint to permit a waterproofing below-
grade membrane to run continuously over the joint.
The problem with PVC waterstops is their susceptibility to improper installation (99%
principle) or damage during the concrete placement. The waterstop must be held in place
properly during the first half of the concrete placement. This is accomplished by a variety of
methods as shown in Figs. 2.18 and 2.19. This situation is not idiot-proof and must be care-
fully monitored for quality control to ensure that the waterstop remains positioned during both
halves of the concrete placement activities. Far too often, the PVC waterstop ends up folded
over, preventing it from functioning properly. In addition, workers installing the reinforcing
bars will often burn, puncture, or cut the waterstop.

TABLE 2.1 Comparison of Various Waterstop Types

Waterstop Type Advantages Disadvantages
PVC Neoprene Rubber ● Rugged and durable material ● Installation can be difficult
Thermoplastic Rubber ● Numerous manufactured shapes ● Tendency to fold over during concrete
placement
Hydrophilic ● Ease of installation ● Subject to damage by rain or other wetting
Bentonite ● No requirement for first half
of concrete placement ● No expansion joint installation
Asphalt Plastic ● Ease of installation ● No expansion joint installation
● Not subject to swelling by rainfall ● Substrate prep required