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468 Barry’s Advanced Construction of Buildings
Jointing and fixing
The use of preformed gasket seals in aluminium carrier systems has developed with changes
in curtain wall techniques so that the majority of composite panels are fixed and sealed in
neoprene gaskets fitted to aluminium carrier systems, fixed to the structural frame as illustrated
in Figure 7.43, Figure 7.45 and Figure 7.46, in which the carrier system supports the
panels and the gaskets serve as a weather seal and accommodate differential thermal movements
between the panels and the carrier system. To reduce the effect of the thermal bridges
made by the metal carrier at joints, systems of plastic thermal breaks and insulated cores
to carrier frames are used.
Where open horizontal joints are used to emphasise the individual panels, there is a flat
or sloping horizontal surface at the top edge of each panel from which rain will drain down
the face of panels. In a short time this will cause irregular and unsightly dirt stains, particularly
around the top corners of the panels unless the panels are pre-coated to be selfcleaning.
The advantage of the single-storey-height box panel is in one prefabricated panel
to serve an outer and inner surface around an insulating core that may be fixed either
directly to the structural frame or a carrier system with the least number of complicated
joints. Some composite box panels of aluminium strip are formed with interlocking joints
formed in the edges of panels. The interlocking joints in panel edges, illustrated in Figure
7.47, comprise flanged edges of metal facing, formed to interlock as a male and female
locking joint to all four edges of each panel. The edge of one panel is formed by a pressed
edging piece, welted to the linings and formed around a plastic insert to minimise the cold
bridge effect at the joint. This protruding section fits into the space between the wings of
the linings of the adjacent panel with a neoprene gasket to form a weather seal.
For this joint to be effective, a degree of precision in the fabrication and skill in assembly
is required for the system to be reasonably wind- and weathertight. As with all panel
systems, the junction of horizontal and vertical joints is most vulnerable to rain penetration
and requires precision manufacture and care in assembly. The interlocking joint system,
illustrated in Figure 7.48, is used for flat, strip steel panels, which are used principally as
undercill panels between windows or as flat panels without windows.
The vertical edges of the strip metal are cold roll formed to a somewhat complicated
profile with the edges of the inner and outer linings either welted or pop-riveted together.
The interlocking joint is designed to hide the fixing bolt and clamp, which connect to the
edge of one panel and are bolted back to the carrier or structural frame. A protruding rib
on the edge of one panel is compressed onto a neoprene gasket on the edge of the adjacent
panel. Horizontal joints between panels are made with a polyethylene backing strip and
silicone sealant. These strip steel panels are made in widths of 900 mm, lengths of up to
10 m and thickness of 50 mm. The steel linings are galvanised and finished with coloured
inorganic coatings externally and painted internally.
7.8 Glazed wall systems
With the development of a continuous process of drawing window glass in 1914 and a
process of continuously rolling, grinding and polishing plate glass in the 1920s and 1930s,
there was a plentiful supply of cheap window glass, and rolled and polished plate glass. In
the 1920s and 1930s, window glass was extensively used in large areas of windows framed