 Chelsea
South West London
Major re-development of a semi-detached residence in an exclusive part of Chelsea.
Contractors Design Services acted as specialist design consultants to Principal Contractor, Westgreen Construction Ltd for the temporary façade retention, the support of the new basement excavation and the piling designs on this project. In consultation with architects Powell Tuck Associates, works consisted of rebuilding the interior and installing an extensive 6 metre deep basement extending under the front and rear gardens as well as beneath the existing house, providing a total area of 315m2.
 All internal areas were removed from ground floor to roof level. Front, rear and side elevations were retained and temporarily supported during construction. Access was provided through front and rear wall, with sway frames installed, supported with Ischebeck Titan micropiles with reinforced concrete pile caps at the four corners and in the centre. To ensure stability, the piles were temporarily braced at intervals as the basement excavation progressed.
The basement was supported by silent sheet piling, designed by Contractors Design Services and installed by Giken Europe BV. This offered significant savings, both in cost and space, from the contiguous bored pile solution originally envisaged. To maximise the space gained, Giken’s ‘Zero’ piles were installed adjacent to party and boundary walls. These were braced with preloaded steel frames to prevent ground movement and provide temporary support to the retained structure and lateral restraint for the Ischebeck Titan micropiles. Monitoring of adjacent/neighbouring properties indicated movements in line with initial predictions.
In what was the first use of a bayonet coupling in the UK, the Ischebeck Titan micropiles were installed using the CDS design from the original ground level, some 6 metres above the intended finished depth of the basement. Reversing the drill’s direction uncouples the pile and enables the drill string to be reused. This method delivered huge cost and safety benefits and Ischebeck Titan received an award for innovation from Construct (Concrete Structures Group) and was a finalist in the 2008 Ground Engineering Awards for Private Sector Project under £1M.
The methods devised by CDS in conjunction with Westgreen Construction Ltd, Giken Europe BV, and Ischebeck Titan allowed the entire project team to successfully realise this ambitious project. |
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