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Cladding and Curtain Wall Construction 443
Column of frame
Web of unit
Undercill rib cleat fixed
to face of column
Support rib
bears on floor
Beam
Hole for
fixing
Horizontal rib to
head of window
Figure 7.24 Under window concrete cladding unit.
or may be in situ cast to provide support and fixing specifically for the undercill ribs of the
units, with restraint fixing through a rib to the floor. The purpose of this arrangement is
where structural columns are widely spaced and it is convenient for casting, transport and
handling to use several units between columns. With the system of under window cladding,
the horizontal windows are framed for fixing to the underside and top of the spandrel
cladding units. The junction of the window framing is usually weathered with gunned-in
mastic as a weather seal. In this construction, it is probably more practical to use a sealed
vertical joint between cladding units than an open drained joint, to avoid the difficulty of
making a watertight seal at the junction of an open joint and window framing.
At the junction of a flat roof and a system of precast cladding units, it is necessary to
form an upstand parapet either in the structural frame or in purpose cast parapet panels.
For a parapet of any appreciable depth, an upstand beam or a concrete upstand to a beam
is formed and clad with purpose cast panels, as illustrated in Figure 7.25. A non-ferrous
metal capping weathers the top of the parapet. In any event, some form of upstand parapet
is formed to avoid a run-off of water from the roof down the face of the cladding, which
would cause irregular, unsightly staining. Where a system of parapet height cladding panels
is used, the panels are cast to provide a top rib that bears on and is secured to the parapet,
as illustrated in Figure 7.25, and restrained by angle cleats between the soffit of the beam
and the panels. A non-ferrous capping weathers the top of the parapet and cladding panels.
As an alternative, a system of special storey height cladding panels designed to extend
over the face of, and be fixed to, the parapet may be used, as illustrated in Figure 7.26. It