Page 307 - Construction Waterproofing Handbook

EXPANSION JOINTS 6.11
Due to adhesion characteristics, foam material adheres to itself, providing seamless
joint applications. It is recommended that joining ends of material be mitered for addi-
tional adhesion. These materials allow for 90° turns with changes in plane, intersections,
and terminations easily and effectively detailed. They are compatible with most building
materials comprising the building envelope. (See Table 6.3.)
Expanding foam sealant systems also make excellent choices for remedial applications.
Existing joints that have failed using generic sealants can usually be easily prepared to
receive a new foam sealant. The joint is prepared by removing the failed sealant, includ-
ing any grinding or solvent wiping necessary to remove traces of old material that remains
on the sides of the joint.
The new foam sealant is then applied into the existing joint per manufacturer recom-
mendations. Applying a sealant over the foam sealant, as described in the Chap. 5 secondary
sealant section, can provide additional protection at the joint.
Figure 6.8 details the use of an expanding foam system involving the addition of a new
wall adjacent to an existing structure. Such locations require allowance for differential as
well as thermal movement. In this detail, a cover is provided as the primary barrier system
with the foam joint acting as a secondary barrier or double-seal protection.

Hydrophobic expansion systems
Combining hydrophobic resins with synthetic rubber produces hydrophobic expansion
seals. Hydrophobic refers to materials that swell in the presence of water. Thus, these mate-
rials require active water pressure to become effective water barriers. They are similar to
below-grade clay waterproofing systems and therefore are limited to below-grade applica-
tions. As with foam sealants, materials are provided in rolls in preexpanded form. Due to
their reactivity with water, materials must not encounter water until after installation.
The use of hydrophobic expansion systems in expansion joints is extremely limited.
Typically, they are used in conjunction with waterproofing membranes to fill expansion,
control, or cold joints in below-grade construction. They are also used as waterstop mate-
rials in concrete substrates.
These materials swell from 2 to 10 times their initial volume. They have low tensile
strength, but their elongation is similar to fluid-applied sealants, with some materials
exceeding 500 percent elongation. As with foam, they should only be used in a compres-
sion mode. (See Table 6.4.)

Sheet systems
Sheet materials are manufactured from neoprene or hypalon rubber goods. They range
from 40 to 60 mil in thickness, and width ranges from 4 to 12 in. Joint expansion and

TABLE 6.3 Foam Expansion Joint Properties
Advantages Disadvantages
Factory manufactured Cost
Seamless application Poor elongation
Ease of terminations Low tensile strength