ENVELOPE SYSTEMS/ElFS
Sealant Failure Due to Delamination
It is common practice to install sealants in panel joints for air and water tightness, with the sealant
applied to the finish coat. However, when the finish coat is exposed to water for an extended length
of time, it will soften. The potential then exists for delamination, in which the finish coat pulls away
from the system. As shown in Figure 4.7.2, from Williams and Williams, such delamination breaks
the air and water seal at the joint. Rather than sealing to the finish coat, Williams and Williams
suggest stopping the finish coat at the panel edge, wrapping the base coat and reinforcing mesh
around the insulation board, and applying the sealant to the base coat. It is also recommended that
low modulus sealants be employed since they will apply less stress to the base coat bond.
UNACCEPTABLE
ACCEPTABLE
Terminate
finish coat at
panel edge
from base coat
Apply sealant to
Substrate
base coat around
insulation board
IONS OF
VERTlCAL JOINTS
Figure 4.7.2 Sealant Joint Delamination (Williams and Williams)
Thermal Bridge at Joint
Because the wall insulation is outside of the structural frame, EIFS have the potential of reducing
thermal bridging of the building envelope. However, the insulation system continuity can break
down at uninsulated panel joints. This can easily be remedied with the addition of insulation behind
the panel seal, as shown in Figure 4.7.3.
UNACCEPTABLE
ACCEPTABLE
Compressible
Break in thermal
insulation at joint
insulation at joint
Figure 4.7.3 Thermal Bridging at Panel Joint
PAGE 4.7-3
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