$ 15 M
726 Hay Street is a 1920’s 8000 m2 heritage structure affected by a long history of roof leaks. Residual design life was explored by core survey confirming a novel history of past extensions and column augmentation; historical consolidation “boney concrete” issues and fully carbonated slabs.
An innovative materials structural design implemented slabs independent of their predecessors with an encapsulating coating under the old slabs to capture future shedding. This approach, whilst not a classic restoration, halved the remedial construction budget and enabled the project to progress.
This project occurred in 2011 and was implemented by Diploma and Duratec. We report it today as opportunities to renovate such structures is rare owing to the trend towards “facadism” where the interior of the original building is generally removed.This commission involved an existing basement, ground and four floored building which was heritage listed. The floor plan size was 53 m x 35 m.
Construction had been staged with Stage 1 of reinforced concrete upon which an extra floor of steel beams and columns with R/C slab had been added. This was sheltered by a steel framed metal deck roof.
At the time of commissioning only part of the ground floor was occupied with commercial tenancies. For many years the upper floors had been unoccupied and neglected. A consequence of this was that the carbonated concrete had been inundated with water periodically causing structural degradation colloquially called ‘concrete cancer’ to be widespread.
The building was surveyed to define the extent of repair required and then repaired with state of the art methodologies.
To adopt the building structure for its intended purpose being offices on the top floors and merchandising on the basement, ground and part first floor, new lifts were introduced and existing escalator openings in-filled structurally. A new escalator servicing the basement and first floor only was installed with associated structural alteration.