From Factory to Public Building

The first hurdle was the change in building occupancy. The factory had previously been designed to earlier building codes but for a small number of occupants – the new functions demanded very high occupancies to be successful which drove a number of design decisions in many construction disciplines.

The Challenges

The substantial increase in occupancy raised concerns with whether the existing floor slab would hold the increased weight. This was especially important as the existing timber piled structure had experienced decades of degradation due to changing underground water levels and subsequent local ground subsidence. The increase in occupancy demanded a higher fire rating of the building superstructure which from a heritage perspective was not permissible with any cladding or painting of the original columns and trusses. The necessary fire rating upgrade needed to be achieved with a more substantial sprinkler system that not only kept the space fire free but also cooled the building structure. This led to the next problem; weight. The existing structure was very light (essentially only a large minimally insulated canopy) and could not easily accommodate the installation of a new more substantial sprinkler system needed for fire purposes but also the new heating and cooling system required. The increase in occupancy not only increased the demand for heating and cooling but also humidity control. If left uncontrolled the increased humidity in the building would lead to condensation, rusting and hastened aging of the building which was naturally a concern for the design team as well as the city heritage department.

Balancing Building Physics

With a combined team including three different MEP design consultants a balance was struck that provided a high level MEP installation performance with the lowest possible increase to the weight the roof would have to accommodate. Having developed a proposed it was then tested against a number sequential collapse scenarios as the roof structure was now working considerably harder than it had in the past. The roof thermal performance also had to be addressed as it was again of balance of what could be realistically done to improve its performance within the constraints of the heritage protection and safety concerns. If we increased its thermal performance too much snow would build up on the roof surface in the winter causing additional weight concerns. If we didn’t improve the roof performance then the building could not be sustainably operated. The roof was composed of solid flatter areas of roof and stepper single glazed lanterns. The optimal solution proved to be to upgrade the glazed lantern areas minimizing the footprint of the areas with increased load (the new glazing would be double glazed in contrast to the much lighter existing single glazing). Naturally solar heat gain also needed to be factored into the new design. Even though the new lanterns are built with a much higher performance than the original lanterns we were able to design them in such a way that visually the heritage department couldn’t easily differentiate the old from new lanterns and as such approved them for installation.

Acoustic Hot Spots

One of the toughest challenges was acoustics – whilst functioning as a factory many decades earlier with few neighbours this hadn’t been a problem so the acoustic performance of the original factory could be very weak. Now that the building is city centre and changing to functions that could be very noisy this was a large concern. Earlier temporary events in the factory had already proven the building fabric provided virtually no acoustic dampening at all. Unable to acoustically insulate the entire roof a number of local acoustics ‘hot spots’ were proposed where noisier events could take place. Different acoustic solutions were applied in each location depending on their exact location and the type of noise likely to be generated. The noisiest locations had free standing ‘acoustic boxes’ built around them; this worked well for the event/music spaces and the cinema spaces. The roofs of the boxes became usable area compensating for their additional build cost. Any other hotspots that could not be enclosed were positioned optimally within the building footprint so that the acoustic calculations could easily prove that the noise levels outside the factory walls and in the adjacent apartments were well within building code.