Abstract:
The paper describes the innovative foundation reuse and strengthening works for two buildings in Central
London. A 1950s building on piled foundations (65 Whitfield St) and a 1930s building (67-69 Whitfield St)
on 3m deep pad foundations were both extended upwards by two new stories. The Client for the project is
Derwent London, with Make as their architect, Main Contractor Multiplex and Engineer Arup. Little was
known about the foundations of either building at the start of the scheme. Extensive investigations of the
existing foundations and ground conditions were carried out in both buildings. At 65 Whitfield St,
investigations identified piled foundations, but found that pile lengths were short and variable. As a result,
strengthening works solutions were adopted whereby the increase in column load was shed into new mini
piles constructed around the existing pile caps. At 67-69 Whitfield St, deep pits were used to investigate the
foundations and reuse was justified based on understanding of the pad dimensions, concrete strength, and
strength and stiffness of the underlying geology. For both buildings the residual risk was closed out through
monitoring during construction. The combined reuse of the structural frame and foundations of both
buildings facilitated a sustainable solution, breathing a new lease of life into outdated buildings.