The proposed development comprises the construction of a new seven storey building providing 17 no. large residential apartments with associated underground car parking, gym, and plantrooms. There will be associated landscaping to the front and rear. On plan the proposed basement is approximately 38m x 32m.
The front of site is bounded by public highway and the remaining boundaries by public footpath, residential buildings (Grade II Listed in part) and gardens, and Christ Church.
The site topography presents a fall of approximately eight metres from the North West down to the South East. Therefore whilst the front of the development will be circa 2m below highway level (which also varies), the rear will be circa 10m below rear garden level.
To enable the development an existing 1950’s nurses home of similar bulk and footprint will be demolished. This building includes a limited services undercroft space, but does not have a basement of significance. The footprint of the existing building is entirely impermeable, as is much of the hard landscaped external space.
Reinforced concrete is proposed for the sub and superstructure of the proposed development.
The basement will be formed by bored cast in place secant piling and multiple levels of hydraulically active temporary propping, progressive excavation to formation level, and then bottom up construction of the RC frame in conjunction with removal of temporary props. Additional bearing and tension piles will be installed where necessary to resist gravity and uplift actions.
The sensitivities of the site and the depth of the basement excavation are such that extensive 2D and 3D ground modelling, and early design of temporary works, were needed to demonstrate the project can be built without any significant impact on surrounding buildings.