Canham Consulting was appointed by Hadley Homes to undertake structural and civil engineering services for the conversion and internal extension of Hadley House, former home of Thetford bus station.
The Grade II listed building had stood empty for some time and proposals involved retaining the existing structural fabric and constructing an internal structure over four storeys to accommodate micro-flats.
Thetford is known to have a rich geological history and before work could commence an exhaustive geotechnical assessment was carried out, which revealed several further issues during the construction process. To address these Canham Construction designed the substructure as an augured piling system, which also helped to avoid significant excavation and disturbance to the original fabric of the building.
The piles required careful positioning to avoid known features under the ground, to mitigate damage to the original structure and to accommodate the geometry and arrangement of the superstructure. A network of cantilevered ground beams were cast over the installed piles to support the superstructure and due to the arrangement of the overall structure, we decided that a steel frame would be utilised for the upper section.
The floor structure utilised a rib-deck system and cast in-situ concrete. Due to limited access and working space made a traditional precast concrete plank floor system unfeasible, likewise, a timber floor was not practical due to the loads, spans, and fire and sound transmission requirements. At ground floor level, the design called for a car park, which necessitated a grillage of columns to co-ordinate with practical car park spaces.
Finally, the roof structure involved a complicated 'gull-wing' effect, which was achieved with the combination of steel frame and timber frame carpentry.
The challenges we overcame at Thetford Bus Station throughout the design and construction periods demonstrated a considered and planned design together with, where necessary, a reactive approach and response.