With little more than a year of bulk earthworks and construction allowed for the phased delivery of the UK’s biggest free school to date, Jonathan Conway embraced prefabrication to close in on the tight programme.
He opted for precast ground beams, lifting their level to the top of the pile caps to eliminate excavation and ground-floor slab-edge shutters alike. Undertaken in winter, these works took the ground floor off the critical path, allowing envelope and frame to progress even in bad weather.
In advance of the main structural frame, he put in a precast lift shaft. Faster than blockwork or plasterboard, it was also safer to construct onsite.
But the biggest offsite-manufactured element of all was the structural frame. Boarded in the factory, it was delivered as panels. Despite the series of meetings needed to iron out the design interfaces and issues, installation was still around a third faster than traditional stud and track. The ability to start the internal fit-out early added to the programme certainty.
Just as well, as right in the preconstruction phase big problems had emerged in the ground of the brownfield site. Although the client had bought a ‘clean’ site, Jonathan rapidly encountered high levels of hydrocarbons in the soil when removing the foundations of a former chemicals factory.
Worse still, he realised that site investigations had failed to identify significant asbestos in the ground. Following a surface asbestos pick under controlled conditions, further trial holes confirmed his fears of extensive contamination. His early works strategy bore fruit here. Instructing no material to be taken offsite, he had the factory foundations grubbed up, crushed and used as aggregate and for the piling mat. He also switched to displacement piling to generate less spoil.
He delivered not merely on time but four weeks early. He didn’t just meet the client’s budget but turned in a company profit on a project that started out as a financial loss. And his use of the BIM 360 digital tool made quality management a practical out-on-site exercise rather than a tickbox procedure. Brimming with compliments, the client awarded BAM a second college scheme.