Architect and Builder Magazine South Africa July/August 2014 | Page 22

With Portside being
located in arguably the
most prominent position
in terms of arrival to the
city it was important that
its appearance be as light,
transparent, harmonious
and unobtrusive as
possible, despite its bulk

The 9th to 19th floors are all open plan
rentable office space belonging to Old
Mutual, and the 29th to 31st Floors are
dedicated to service plant.
In order to access these levels, whilst
addressing
vehicular
and
pedestrian
approach, corporate security and dual
entrance addresses, the core of Portside
accommodates a complex array of lifts. Both
owners have dedicated shuttle lifts which link
their respective parking floors to their foyers,
and the office floors are then serviced via six
dedicated lifts each. Portside has a total of
22 lifts altogether, including a service lift and
fireman’s lift.
Although both FirstRand and Old Mutual
specified 2,700mm clear floor to ceiling heights
on their respective floors as well as 800mm
deep ceiling voids for service reticulation,
FirstRand further stipulated that their portion
of the building be fitted with 250mm deep
raised access flooring for additional electrical
and data reticulation, whilst the rentable floor
plates of Old Mutual received only a cement
screed finish. The effect of this is that the
floor to floor height of the tower changes
from 3,850mm to 4,050mm from the 20th
floor upwards. The additional height is taken
up in the spandrel panels of the curtain wall,
between the floors. Interestingly, this is not
perceptible in the external elevations.
Façade
From the outset, Portside was intended to be
clad with a fully glazed curtain wall façade. As
a contemporary material with almost limitless

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scope, glass typifies the nature of the building
as a AAA grade office environment and as
a corporate head office. With Portside also
being located in arguably the most prominent
position in terms of arrival to the city as well as
it being intended to be the tallest building in
the city, it was important that its appearance
be as light, transparent, harmonious and
unobtrusive as possible, despite its bulk.
The initial proposals for Portside depicted
a light grey, silvery metallic hue to the glazed
façade. However, on viewing full-scale samples under various weather conditions it was
noted that the grey body tint appeared at
times far darker than anticipated. Considering
the sheer volume of Portside, an Azure glass
was proposed by the architects as a more
appropriate solution that would appear less
harsh and imposing.
The fenestration requirements for Portside
were to both capitalize on the spectacular 360
degree views of the city, particularly when
viewed from a height, as well as to maintain an
optimally comfortable working environment
through an efficient integration of the façade
with the HVAC and lighting systems.
Although architecturally conceived as a
fully transparent curtain wall, the initial façade
concepts struggled to comply with the thermal
mass that would be required in relation to
the mechanical requirements, which placed
limitations on the extent of vision glazing
achievable. A portion of the northern and
western façade therefore needed to be glass
cladding over an inner thermal skin. Through
an extended design development process,

Portside