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Cladding and Curtain Wall Construction 441
wind pressure. The restraint fixing most used is a non-ferrous or stainless steel angle cleat
that is either fixed to a slotted channel cast in the soffit of beams or slabs or, more usually,
by expanding bolts fitted to holes drilled in the concrete. The cleat is bolted to a cast-in
stud protruding from the horizontal rib of the unit, as illustrated in Figure 7.21. The slotted
hole in the downstand flange of the cleat allows some vertical movement between the frame
and the cladding.
Another system of fixing combines support fixing by dowels with restraint fixing by
non-ferrous flexible straps that are cast into the units and fit over the dowel fixing. Support
and restraint fixing may be provided by casting loops or hooked ends of reinforcement,
protruding from the back of cladding units, into a small part of or the whole of an in situ
cast concrete member of the structural frame. The disadvantage of this method is the site
labour required in making a satisfactory joint, and the rigidity of the fixing that makes no
allowance for differential movements between structure and cladding. At external angles
on elevations, cladding units may be joined by a mitre joint or as a wrap-around corner
unit specially cast for the purpose, as illustrated in Figure 7.22.
The advantage of the wrap-around corner unit is that the open drained joint may be
formed against the solid background of a column, and the disadvantage of this unit is that
Corner unit
to column
Storey height
cladding units with
open drained joints
Corner units with
mitred edges
Figure 7.22 Corner units to concrete cladding.