Old War Office, London – Projects
Hotel & Leisure
- EPR Architects
- 57 Whitehall S.A.R.L.
Elliott Wood were appointed as structural and civil engineers for the ambitious refurbishment of the Grade II* listed Old War Office. This involved the refurbishment and conversion of the existing Ministry of Defence offices into a luxury London hotel and residential apartments with a mix of one to three new storeys constructed above the original roof and four storeys of new basement below the existing two storey basement.
Structural proposals have been developed to take advantage of the opportunities that the site offers without detriment to the historic fabric, introducing new basements beneath the existing courtyards and respecting the loadpaths of the surrounding stone facades. Appraisal works demonstrated that the existing structure could accommodate up to three additional storeys, strategically arranged to ensure that these are unseen from street level.
With the existing building fully captured with a 3D survey, this information is being used and manipulated to create a full model of the existing and proposed structures, clearly communicating the complex structural interventions.
In addition to the traditional civil engineering works packages, Elliott Wood conceived an innovative solution to remove the need for tension piles that would otherwise be required to overcome the uplift created by the long term hydrostatic pressures within the London Clay.
Working closely with geotechnical specialists, a suite of testing was undertaken that provided the parameters that enabled Elliott Wood to design a permeable layer under the basement slab. This permeable layer permanently dewaters the basement slab, removing the hydrostatic pressure.
Geotechnical analysis and testing was used during negotiations with Thames Water to achieve a bespoke agreement to discharge the ground water to their sewer.
The system saved approximately 36 no. 900 diameter tension piles each 30 metres long which would have been either installed as plunge piles from the original basement level or installed at the new basement level which would have been a complex and time consuming operation.