Responsibility for producing precast concrete arch shells which reproduced the existing masonry arches fell to Northern Ireland-based Macrete.
Preliminary surveys had established that the bridge's presumed symmetry about the centreline of the central span did not really exist. Each arch was slightly, but significantly, different. A detailed laser survey was essential before final design could begin.
Stonemasons from Essex-based Universal Stone took rubbings of all stone elements on the existing facade. In a hired hall these rubbings were then matched up with a profile of each arch, plotted from the laser survey. As Macrete developed templates for its shutters, these were sent over to Kingston and checked against the plots as well.
Arch elements are 1m wide and extend from the springing points to the centre of the arch. Match casting ensures accuracy and cast-in brick slips duplicate the original masonry. The largest unit weighs 13t.