Joint Sealants
CSI Division 07, Thermal & Moisture Protection
Flexible sealant compounds, such as silicone or polyurethane, installed at building joints, control joints, expansion joints, and the perimeter of windows and doors, engineered to accommodate the specific amount of movement that joint is expected to experience without losing its seal, distinct from a rigid material that would crack under the same movement.
Why it matters
Different sealant chemistries are rated for different amounts of joint movement and different substrates, using a sealant rated for less movement than the joint actually experiences, or one incompatible with the specific substrate, leads to a bond failure well before the sealant's rated service life is up.
On a real project
A glazing contractor seals a curtain wall's expansion joints with a structural silicone sealant specifically rated for the joint's calculated range of movement, confirmed compatible with the specific glass and frame substrates through the manufacturer's adhesion testing.
Who this matters most to
A Glazier or specialty caulking crew installs sealants at window and curtain wall joints. A QA/QC Inspector may require a field adhesion test, a pull test, before a sealant installation is approved for the whole building.
Where this goes wrong
A contractor uses a lower-cost general-purpose sealant at a building's primary expansion joints instead of the higher-movement-rated sealant specified. The joint's actual seasonal movement exceeds what the substituted sealant can accommodate, and the bond fails within two years, well before the original sealant's warranted service life would have ended.
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