Page 291 - Construction Waterproofing Handbook

SEALANTS 5.49
Bond breaker tape is installed as shown
in Fig. 5.52 to allow contact area length to
substrate equal to that of frames.
Typically, the contact area length should
1
be 2 in. In curtain wall construction or
storefront perimeters, based on movement
capability of sealant, this length may be
increased to allow larger joints. Figure 5.53
shows glass perimeters sealed with the
use of “quarter-round” premanufactured
FIGURE 5.51 Incorrect metal-frame sealing. backer rod.
Any gap or space between frame and
substrate should first be filled with a
caulking material. This provides a firm
substrate on which to apply bond breaker
tape. The sealant should then be tooled flat
with a straight edge over the caulking.
Table 5.12 summarizes the preferred
installations for the major generic sealant
materials.

GLAZING

Glazing refers to the use of silicone
FIGURE 5.52 Correct metal-frame sealing.
Distance A should equal distance B. sealants to adhere glass, metal, tile, and
other finish materials to the structural
components of a building envelope.
Silicone materials are used for glazing
because of their excellent adhesion quali-
ties, with manufacturers providing war-
ranties for up to 20 years.
Glazing can have structural properties
when it acts as the primary attachment
mechanism of the facade component to the
FIGURE 5.53 Proper application of perimeter structure. Glazing can also function as a
joint using fillet backer rod. (Courtesy of Nomaco) nonstructural application, in which the
glazing is used to seal the glass or other fin-
ishes for a weathertight envelope.
While the primary purpose of glazing is
adhesive attachment, it also provides a secondary purpose of acting as a waterproofing bar-
rier at the joints in the facade materials. For structural applications, high- or medium-high-
modulus materials are used to provide effective adhesion capabilities, since the high
movement capabilities of a low modulus material are of secondary importance. In non-
structural glazing, the low modulus materials are typically acceptable.