Location
Royal Borough of Kensington & Chelsea
Main Contractor
Keltbray Ltd
Value
£23.4m
Project Length
Introduction

The K1 Knightsbridge project was a complex façade retention and structural demolition scope which included numerous Grade ll listed elements. The site was bound by the busy Brompton Road, Sloane Street and Basil Street which required many interfaces with London Underground, RBKC, TfL and local stakeholders.

The K1 Knightsbridge project was a complex façade retention and structural demolition scope which included numerous Grade ll listed elements. The site was bound by the busy Brompton Road, Sloane Street and Basil Street which required many interfaces with London Underground, RBKC, TfL and local stakeholders.

Furthermore the site was located directly above the Knightsbridge London Underground Tube Station (the eastern entrance was within the site boundary). To the west of the site were 3 disused London Underground ventilation shafts which were protected throughout the works. The shafts were 8m in diameter and 25m deep. London Underground housed the signal control equipment for the entire Piccadilly Line within these shafts.

The project was carried out in two phases. Phase 1 consisted of the installation of temporary works to neighbouring properties, asbestos removal, soft strip, stonework salvage and enabling demolition to establish a new site entrance for Phase 2.

Phase 2 consisted of the installation of the façade restraint system (FRS), installation of site hoarding, asbestos removal, soft strip, extensive heritage salvage consisting of stonework salvage and façade cleaning, movement monitoring, substantial underpinning and basement propping, structural demolition to the underside of the basement slab, removal of below ground obstructions and installation of the piling platform.

In addition to the aforementioned works, Keltbray Piling was also engaged by Skanska (incumbent Principal Contractor) to undertake the installation of the secant piled wall and all new foundation piles required for the project prior to the commencement of the basement excavation works. Coordinating the commencement of the piling operations with the completion of the demolition activities within the confines of a fully retained façade was challenging but with Keltbray responsible for enabling and piling operations, the interface challenges were managed and the works successfully completed.

All perimeter scaffolding was encapsulated with Monarflex Monaro Sound to minimise noise impact on the local community. During Phase 2 an existing LUL ventilation duct was diverted without any disruption to LUL. The majority of the FRS and hoarding installations were carried out during nights shift to enable the footpaths to be operational during the day. Due to the close proximity of the LUL assets, 3 different methods were used to establish suitable anchorage for the FRS. These included mini piling in the footway of Basil Street and Hoopers Court directly above the LUL disused tunnels, concrete mass filled vaults at basement level and concrete plinths at street level.

Underpinning was completed beneath the retained façade. The underpins were excavated by hand to a depth in excess of 4m and carried out prior to any demolition taking place. The underpinning was further reinforced by installing raking props and thrust blocks that were installed below the proposed basement slab level.