Steel Construction Vol 40 No 2 - Tubular Steel Feature | Page 32

SAISC SUBSIDIARIES: SAMCRA

Post construction installations
on roofs and service access
On occasions when we have been invited

support systems that utilize concrete

to inspect a roof over a shopping centre

blocks as ballast which can considerably

we are stunned by the amount of post

increase the loading to the cladding and

construction activity the roof is subjected

supporting steelwork. Fire vents are

to. This can vary from the inappropriate

frequently attached to and supported by

installation of aerials, ventilators, extractor

the cladding in a manner that impedes

ducts, air conditioning units and more
recently alternative energy systems.
Damage from regular foot traffic is another
cause for concern.
by Dennis White, Director, SAMCRA

The vast majority of roof structures are
designed as inaccessible with imposed

the thermal movement of the cladding. In
addition to the increased risk of crevice
corrosion at the interface of the supports
with the cladding plus the accumulation
of debris around the supports there is
an increased risk of flooding of the pans

loading based on access for the installation

during heavy rain. Inadequately designed

of the cladding and thereafter maintenance

back-flashing to fire vents (which are over

of the cladding system and gutters only.

a metre wide) contribute to the flooding of
adjacent pans. The placement of conduits

Occupancy within shopping centres is

and pipes in pans pose similar problems.

transient which gives rise t o changing

Such obstructions can also cause the

demands for services such as extractor

accumulation of hail, resulting in flooding.

fans and ducts for restaurants, fire vents

Whilst cable trays laid transversely across

and auxiliary air conditioning units.

the cladding ribs near gutters may prevent/

Most extractor fans require a 600mm

reduce the flow of hail into unguarded

square opening in the cladding which is

gutters the accumulated hail behind

positioned randomly between purlins,

the tray can exceed the design loading.

often without any additional supporting
steelwork, the fan and duct are supported
by the cladding. Regularly the painted
steel supports with small base plates are
placed directly in the pan of the cladding,
invariably between purlins. Occasionally
raw wooden blocks are used as bearers.

www.samcra.co.za

The loading from foot traffic during
the installation of these items if often
much higher than that associated with
maintenance of the cladding.
Sections of these roofs are subjected

The support frames for solar heaters

to regular high levels of foot traffic for

pose an even greater risk as the loading

maintenance of non-cladding items

is much greater. Some PV panels have

resulting in considerable damage to
the cladding and flashings. Areas most
susceptible to damage are the points of
access onto the roof, jumping from one
level to another, eaves and areas behind
parapets which are used as hoisting points
together with access for cleaning windows,
etc. These areas need to be protected with
suitable designed ladders, platforms and
walkways.
In all cases the protective coating/s to the
cladding system suffers irreparable damage
thereby greatly reducing its durable
working life.

30 Steel Construction Vol. 40 No. 2 2016