Introduction
Groundfcore Shorco supplied a complex shoring solution to a three-level basement construction as part of the redevelopment of Amberwood House in Knightsbridge, to transform it into one of London’s most unique and palatial private residences.
The building which was formerly the Panamanian Embassy and home of legendary ballerina Dame Margo Fonteyn and her ambassador husband Dr Roberto Emilio Arias, is being redeveloped by S Walsh and Sons on behalf of the K10 Group, who are transforming the historic property into a magnificent 15,300 sqft private mansion. Once completed the 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. The property is expected 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. Groundforce was appointed by specialist contractor S Walsh & Sons to provide heavy-duty shoring equipment to support the sensitive basement excavation element of the project.
The project required a complete re-modelling of the building’s interior. S Walsh used a combination of underpinning and secant piling to create a support for the four facades while excavating the three-level basement below.
Challenges
Amberwood House is located down a gated drive directly opposite the Victoria & Albert Museum. This secluded location made access extremely difficult and created a unique challenge for Groundforce, explains Nadir Salim, Groundforce’s major projects engineer: “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.”
Solution
Due to the proximity of the surrounding buildings the site was extremely confined which limited what machinery could be used. With not enough room for large plant, all deliveries had to be reliable and on time as there was only room for one wagon at a time for the entire site.
Groundforce’s equipment had to be lifted and installed using a small excavator, which meant that with nothing could weigh more than 2.2 tonnes This meant splitting the props into small sections where they were assembled at ground level during installation.
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.
Paul McGeady, construction operations manager for S Walsh said, “As a specialist in basement projects in London we have 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.”