Neilcott Construction Limited

PRIME HOUSE

Occupied Site

Steel Frame

Network Rail BAPA

Info box:

Client: Tindall Overseas
Architect: Jestico & Whiles              Quantity Surveyor: LG Partnership
Value: £3.6m

Neilcott was responsible for the construction of a new two storey office block built over a Network Rail tunnel, located less than 1500mm below ground level. Strict methods of working set out in a BAPA were imposed by Network Rail which dictated that no load could be imposed upon the tunnel lid during construction.

The existing buildings consisted of a largely five-storey building fronting Finchley Road (The Front Building) and a largely one storey extension (The Rear Building) behind which was the location for the two storey office extension.

The Front Building comprises ground and first floors in use commercial by Alied Irish Bank together with access to residential use over at second to fourth floor levels.

This residential element remained occupied during the Works and due allowance for the continuing proper, safe, secure access and occupation of this residential element was made throughout the course of the works including maintaining all services including all air conditioning, ventilation and cooling systems and maintaining liaison with the residents throughout.

Foundations comprised piles installed alongside the tunnel with capping beam. Insitu concrete ground beam spanning 20m between capping beam were constructed using falsework suspended from pairs of pre-cambered steel sections, prior to post tensioning in the final position. Infill between the beams was formed using an omnia permanent formwork system. The structure for the extension was supported upon specialist bearings inserted between the piled substructure and the superstructure in order to eliminate transfer of noise and vibration from the rail tunnel to the completed building.

With no possibility of intermediate support across the 20m span the first floor structure was suspended from steel trusses at roof level. A glazed atrium area joined the new building to the existing development.