Cambridge House, Piccadilly - Staircase Support
About the Project
The Former Lord Palmerston residence, and subsequent Naval and Military “In & Out” Club, together with surrounding buildings are being converted into a Luxury Hotel and Private Residences. Deconstruct (UK) Ltd.’s £37m redevelopment package involves the demolition of the existing structures, retention of the Listed façades and staircase structure, with piled excavation of4 levels of basements, and subsequent building reconstruction.
The main staircase to 90-93 Piccadilly is a Listed stone cantilevering staircase and needed to be protected and supported during the basement excavation works, whilst allowing space for the construction of a secant piled wall beneath.The propping of the adjacent façade on to the support structure added to the complexity of the project.
The scheme required the use of 14nr 508/450mm diameter piles up to 26.2m depth, with both compression, horizontal and tension loading, and full length 6B32 cage coupled together in short sections and a 5.4m long 203
x 203 x 86kg/m UC plunged in the top. Piles were installed using a Soilmech SM4 restricted access piling rig which was sized to access the corridors and available working space.
The bearing piles were highly loaded (687kN max / -280kN min Combination 1 design action) and had to be designed from a low formation level, as the area beneath the stairs were being excavated to a depth of 17m. Reinforcement materials had to be provided in short sections and manually-handled through the building before being lifted in to place and lowered down the pile with a 2t hoist. Due to the access and working space being minimal, the piles were installed in narrow corridors and doorways, and working access needed to be considered and provided for each discreet pile position by making local modifications to the existing structure.