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478 Barry’s Advanced Construction of Buildings
Double glazed unit
Frame of glazed
panel
Silicone joint seal
Silicone edge seal
Silicone
adhesive
Spacer
Figure 7.54 Four-sided structural sealant.
Structural glazing systems are designed to give a flush façade of glass with the supporting
mullions and transoms of the carrier frame just visible through a transparent glass façade.
The extent to which the carrier frame is visible will depend on the intensity of light reflected
off the surface of glass. For structural silicone to be most effective in bonding glass to the
supporting framework, it should be applied in conditions where the cleanliness of the
surfaces to be joined, temperature and humidity can be controlled.
Two-sided structural silicone glazing is used for the two vertical edges of single glass
panes which are bonded to a metal frame fixed to mullions of a curtain wall system and
supported at their base and restrained at their top edge by aluminium transoms. The wind
forces acting on the glass are carried by the framing back to the carrier system, and the
weight of the glass by the transoms of the curtain wall. Structural glazing to IG units may
be applied to the inside face of the inner sheet of glass in the form of four-sided glazing
bonded to an aluminium panel frame, as illustrated diagrammatically in Figure 7.54. The
edge seal to the spacer bars between the glass in the IG units is made with silicone sealant
to provide the most effective seal against penetration of water. As there is no means of
bonding the outer glass to the frame, the outer glass is held in place by the silicone edge
seal. The bond of the edge seal will be insufficient to retain the outer glass firmly in place