To create the brick exterior of The Hotel Britomart, the team at Cheshire Architects have used an innovative technique that’s a New Zealand first – and an important part of the hotel’s quest for a 5 Green Star rating.
It took a long time for Cheshire Architects to find just the right brick for the exterior of The Hotel Britomart, now under construction in Galway Street. Brick is a fundamental element of Britomart’s landscape, one that has been carefully preserved, restored, repeated and reflected in many ways through the nine blocks of the precinct. So it made sense to incorporate it in the facade of the hotel as a way to honour “the last of Auckland’s rich built heritage in one place,” as Nat Cheshire puts it.
“Any building that went into this site would be foolish to ignore the deep, rich conversation with the buildings around it,” says Nat. To his eye, that meant creating something that would not only relate to both the Buckland and Masonic buildings next door (which are both being refurbished as part of The Hotel Britomart project), but stand in contrast to the glass “curtain wall system after curtain wall system” that Nat says forms the backdrop of the wider city.
Brick is not, however, a material that’s well-suited to building a 10-storey tower; the Cheshire Architects team needed a more earthquake-resistant system. What they chose was a pre-cast concrete panel system with bricks cast into the exterior which would function as both cladding and structure for the building. “It’s a system that’s been used for four or five decades overseas, but never before in New Zealand, mainly because of our high earthquake risk and certainly not at this scale,” says Nat. “We’ve been through some really intensive processes, including putting those test panels under enormous stresses to ensure that we know everything about how they behave.”
For the brick itself, Nat and the Cheshire team first looked to New Zealand, but even the largest brick manufacturers were unable to supply to the sheer scale (more than 150,000 bricks) of the project. One appealing option came from Belgium but, mindful of the environmental impact of shipping from the other side of the world, the team eventually settled on a brick manufactured in Victoria, Australia from the local clay there.
“We originally imagined the colour of the bricks being darker, but the kiln firing process to get them to that depth of colour made them more brittle,” says Nat. “Now we’ve fallen in love with the soft, ochre-grey tone that feels like it better bridges the warmer tones of the existing brick buildings around it and the pale grey natural plaster of the Australis Nathan building where Tiffany & Co are.”
After being manufactured in Australia and cut down to the thickness required for the concrete casting process, each brick is laid face down in an extremely precise grid of CNC rubber moulds – a little like delicate egg crates – at the precast concrete factory in East Tāmaki, and the concrete is cast over the bricks to form the back of the wall panel when lifted into vertical position. In line with The Hotel Britomart’s commitment to sustainable building and goal of achieving a New Zealand Green Building Council 5 Green Star rating, the concrete used is an ‘enviro-crete’.
“Demolition concrete has been crushed and recycled into the concrete mix,” says Campbell Williamson, development director for Britomart. “We also use a significant proportion of recycled water and we have avoided some of the typical concrete mix components, all to give us an environmentally better concrete.”
Over the coming months, new floors of rooms are expected to be added at a rate of about one every three weeks. “It’s kind of magical,” says Nat Cheshire. “What’s going to emerge more and more is the scattering irregularity of the windows rising up with the facade. At the lower levels, the windows are rectangular and tall to match with those of the heritage buildings in Britomart. But as the building rises above the parapets of the heritage buildings, the windows dissolve into a constellation of varying sizes. An environmental benefit of not being a glass curtain-wall building is that we’re choosing where we let the sun in, which means that the stresses on the environmental control systems are much less, and there’s less need for electricity for air-conditioning to cool the rooms down inside.”
The flush glazing system used for the windows means that the panes will sit aligned with the outside face of the bricks.“From the street, you’ll see a very thinly edged panel of glass, very precise and tight against the lumpy texture of the bricks,” Nat explains. “Sleek and modern up against historic and textured – that’s kind of the Britomart story in one.”