We have a long history with this site in Hampstead. Following several earlier schemes by previous clients, the site finally gained planning permission, on appeal, in 2015 for the construction of a new build private home. The new house has seven bedrooms over three-storeys, with living areas at lower ground floor and pool, plant and recreational areas in the basement. Varying levels across the site mean the ground floor is the only storey fully above ground, with the lower ground floor below ground on three sides, and the basement fully below ground. This was a conscious decision – the building form aims to make use of the various change in levels in the site as a means for integrating the architecture and landscape and minimising the building mass for surrounding neighbours who have rejected all previous attempts to replace the neglected and abandoned house that was on the site.
Our initial scope of works was to support the planning application. The London Borough of Camden require detailed engineering input to produce a Basement Impact Assessment (BIA) for all subterranean development, no matter how insignificant, for submission with the planning application. We also commission and coordinate the geotechnical and hydrological specialist input required for this Assessment. Alongside this work we produce a Construction Method Statement, as well as construction sequence and logistics drawings to accompany the structural design of the final building.
After planning was granted by the Council we were obliged to submit a Detailed Basement Construction Plan (DBCP) as part of the Section 106 agreement. The DBCP is an enhancement of the BIA. Detailed and final design is undertaken for the temporary and permanent works, monitoring is agreed and surveys are carried out to the neighbouring properties prior to any works starting on site. This plan was also independently checked by a third-party engineer before it was submitted to the Council.
Additionally, in conjunction with the planning requirements, we had to undertake a diversion of the Thames Water sewer that runs through the site. The diversion became the first works to be carried out on site and as such became the critical path for the construction programme. The basement was then constructed by completing the piling at high level and following a traditional bottom-up sequence for the basement, propping the secant wall as the soil was excavated.
The project was a Design & Build contract and during construction we were maintained by the client team to monitor the works by the contractor in the shell and core phase.