Groundforce Shorco has supplied heavy-duty shoring equipment to specialist contractor S Walsh & Sons for use in a highly-sensitive basement project in London’s Knightsbridge district. S Wash & Sons is carrying out the redevelopment of Amberwood House, formerly the Panamanian Embassy and home of legendary ballerina Dame Margo Fonteyn and her ambassador husband Dr Roberto Emilio Arias. Kam Babaee, CEO of the K10 Group Ltd, London’s leading high end property developers who are behind the development, describes the property as a palatial and unique residence. Once completed the 15,300 sq. ft luxury private mansion, will include a cinema/ clubroom and a grand 12 metre swimming pool room which will be the largest private swimming pool in Knightsbridge. Amberwood House is soon to go on the market for an estimated price of £75m. A major part of the transformation and enlargement of the three-storey building is the addition of a three-storey basement.

Difficult access

Amberwood House is located down a gated drive directly opposite the Victoria & Albert Museum but its secluded location makes access extremely difficult. “All deliveries had to be reliable and on time as there was only room for one wagon at a time for the entire site,” explains Nadir Salim, Groundforce’s major projects sales engineer. “Due to the proximity of the surrounding buildings the site is extremely confined which limited machinery as there wasn’t enough room to physically have large plant.” This meant that all kit had to be lifted and installed with a small digger. “We therefore had to ensure that all components were within lifting capacities of this small digger with nothing weighing more than 2.2 tonnes. This meant splitting the props into small sections where they were assembled at ground level during installation,” explains Nadir. The project has involved the complete re-modelling of the building’s interior. S Walsh therefore used a combination of underpinning and secant piling to create a support for the four facades while excavating the three-level basement below: “We’re working in a deep excavation with a building suspended over our heads!” he says. This created a unique challenge for Groundforce, says Nadir: “We’re very used to working on new, modern commercial large-scale basements in central London where access is not a major issue. “On this project, while the propping itself wasn’t too complicated, it was what we were propping and the lack of space in which to work that were the real challenge. The whole project has a very ‘bespoke’ feel to it due to the one-off nature and the extreme physical confines. Basically, the excavation covers the entire footprint of the site.” Groundforce supplied a combination of its MP125, MP150 and MP250 modular props (125, 150 and 250 tonnes capacity respectively) and its Mega Brace system to support the secant piled retaining walls of the building. The smaller props were equipped with 508mm diameter extension tubes while the MP250s employed the larger 610mm tubes. “Deflection criteria were very strict,” says Nadir. Any significant ground movement was likely not only to cause damage to the retained facades of Amberwood House but potentially also to surrounding buildings. As a specialist in basement projects in London, S Walsh has used Groundforce equipment on numerous projects in the past. “We use them very frequently and on this job we knew exactly what was needed and Groundforce was the obvious choice” said Paul. “We also worked very closely at early design stages with the planning department of the Borough of Kensington & Chelsea to ensure that the restoration and enlargement of this historic building will result in a truly magnificent development, and due to new building restrictions being brought in by the Borough of Kensington & Chelsea for this type of development, it might be the last major project of this type in this part of London.”