Construction & Engineering The considerable challenge for the main contractor , WBHO , was to construct a 21 storey building on a relatively small site of ± 45m by 83m with various restrictions due to the three neighbouring buildings and a
busy Grayston Drive in central Sandton on the fourth boundary . Due to the restricted site access and the variable rock on site the tight program deadlines was always going to be challenging , even though the main contractor managed to erect three tower cranes on the small site .
The lateral support for the five level deep basement was constructed using 600mm diameter piles with 200mm gunite arches that extended 17m in depth at the South face into the typical Sandton soil profile . This soil profile was a combination of soft sand and soft weathered granite rock with a hard Diabase intrusion requiring blasting lower down slowing down the program . Due to the variable nature of the founding conditions a combination of piles and pad footings were chosen for the foundations and these could only be finally determined as the excavation depth was near completion allowing piling contractor , Franki Africa , to probe the rock level .
The main structure has five basements and six levels of parking above ground with ten levels of office space above that on a grid of 8.4m by 7.6m . The parking slabs were constructed with 230mm post-tensioned slabs and the office slabs were 270mm post- Tensioned . The main stability elements were the central core and two smaller stair shafts at either end providing lateral stability to the long building .
On the north side of the building the floor plates from office level 3 upwards to level 9 project out gradually in increments of 1.48m into the Atrium space with raking columns as supports . One of the many structural challenges was to carefully model the future
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