283757893275

472 Barry’s Advanced Construction of Buildings
Spigot bolted
to roof
Head bolted
to spigot
Lugs cast
into
floor
Spigot fits in
mullion
Lug bolted
to box
Glass fixed
to wings
with beads
Spigot
fits
mullion
Aluminium mullion
Transom fits
spigot
Spigot fits
mullion
Cill fixed to base
Figure 7.50 Aluminium curtain walling.
that was in vogue in the 1950s and 1960s, and the hollow or open section transoms with
a ready means of jointing and support for glass. Hollow box section mullions, transoms
and cills were generally of extruded aluminium, with the section of the mullion exposed
for appearance’s sake and the transom, cill and head joined to mullions with spigot and
socket joints, as illustrated in Figure 7.50. A range of mullion sections was available to cater
for various spans between supporting floors and various wind loads. The mullions, usually
fixed at about 1–1.5 m centres, were secured to the structure at each floor level and mullion
lengths joined with spigot joints, as illustrated in Figure 7.50. The spigot joints between
mullions and mullions, and between mullions and transoms, head and cill, made allowance
for thermal movement, and the fixing of mullion to frame made allowance for differential
structural, thermal and moisture movements. Screw-on or clip-on beads with mastic or
gasket sealants held the glass in place and acted as a weather seal. This form of curtain
walling with exposed mullions was the fashion during the 1950s, 1960s and early 1970s.