New Houghton office block:77 foundation piles installed

Gauteng Piling was entrusted with the provision of foundation piling for a new luxury office block development in Eighth Street, Houghton (fronting onto Oxford Road), currently being built and developed by the Barrow Group.

Ivan Schlapobersky of M/Architects in Illovo, who designed the building which will feature close to 2,900 m2 of office space, says the site on which the new upmarket office block will be located was previously a residential property. “The house was demolished and had been vacant for some time. Great care is being taken to preserve existing trees on the periphery of the site,” Schlapobersky stated.

Kobus Geyer, site manager for Gauteng Piling, says the foundations for the four-storeyed office block (with double parking basement levels) on a site of over 1000 square metres, called for 77 auger cast in-situ piles, varying between 14 to 18 m in depth. The diameter of the piles varied: 27 are 500 mm in diameter, 11 are 600 mm, 19 are 750 mm, and four are 1100 mm in diameter.

Auger cast in-situ piles are formed by drilling holes into the ground, placing steel reinforcement into the holes, then filling the holes with concrete. In built-up residential areas, such as Houghton, auger cast piles cause minimal disturbance and are generally favoured for environmentally sensitive sites.

Steel reinforcement employed for the piles consisted of seven high tensile strength steel bars (7Y32), 32 mm in diameter; and spirals of mild steel, 8 mm in diameter with a 200-mm pitch. The rebar cages inserted into the piles were 950 mm in diameter and 4.33 m in length.

“In addition to the 77 foundation piles, in November 2014 – prior to site excavation and earthworks in January this year – Gauteng Piling provided 13 earlier piles to provide lateral support for a retaining wall against the site’s neighbouring property to the north,” Geyer added. “The piles will eventually form part of a retaining wall, sprayed with Gunite, a mixture of cement, sand, and water, through a pressure hose to produce the strong ‘lining’ of the retaining wall.

“Such a specially-designed bored pile retaining wall system makes it possible for developers and contractors to make maximum use of available space in excavated structures with underground levels. The bored pile solutions minimise the need for additional support measures and maximise the available excavation.”

Gauteng Piling employed two rigs for the piling project for the Eighth Street site (which is adjacent to Oxford Road): a Williams LDH digger with 5,5t-m torque, and a Soilmec hydraulic drilling rig.

Two prominent Gauteng Master Builders are closely linked with Gauteng Piling. The company was established in 1996 by former MBSA and MBA North president, Nico Maas (current chairman of GP), and is now run by MD, Hennie Bester, who has served as president of MBA North for an unprecedented three-year spell from 2011 to 2013.

Gauteng Piling has in the past 18 years completed over 1,500 projects to become one of the major players in the piling industry in Gauteng. The company now has a fleet of 20 auger drilling machines, two cranes, two bore rigs, four Grundo hammers, and two lateral support machines.

More information from Hennie Bester, Tel: +27(0)11 465 7751 / www.gautengpiling.co.za