Solid Foundations
A time-honoured building system in Europe is being utilised to craft homes that embody a heritage-worthy essence.
Words Casey Vassallo
Photos Jahl Marshall
Homes are meant to be sanctuaries of security, comfort and lasting memories, where loved ones gather to create cherished moments to last generations. At least this is the dream Chris and Robyn MacPherson are striving to create for more people with Stellaria, a company dedicated to premium building materials.
Chris, who started out in landscape architecture, established MacPherson Architecture in 2000 and has been designing thoughtful high-end and lifestyle homes for over 25 years. On the other hand, Robyn was studying law when the Great Recession of 2008/09 hit and made the pivotal decision to come into the fold. Together, they form an exceptional team with a passion for alternative building materials.
Along the way, the couple have designed homes using all systems such as concrete, mudblock and rammed earth – but much of it was arduous according to Robyn. That all changed when they discovered Porotherm clay block from Wienerberger, an Austrian-founded company.
“We both looked at it and by the extruded honeycomb nature of the
block, we could just see immediately how it worked,” Robyn says. “We could see that it had the ability to do everything we try so hard to achieve.” From there, they began nurturing a relationship with Wienerberger to become their New Zealand partner, and in late 2014 Stellaria launched.
Porotherm clay blocks are a structural walling system that can be used in place of materials like timber frame with insulation. Imported from France, there’s a main Porotherm clay block, a portal block, and a lintel block, each taking on an intricate honeycomb matrix structure. Only the portals and lintels are filled with steel and concrete to form the structural elements, being a confined masonry construction system. The rest are installed as a typical concrete block, bound using a Dryfix adhesive instead of mortar. The exterior of the home can then be clad in any fashion, to meet the New Zealand Building Code.
“It's such a simple, efficient system. There's very little complexity around
the walls, and the blocks go up really fast,” Robyn says. It’s said to be faster to construct a building from Porotherm, and a site uses less water and produces less waste given it’s a straight-forward and natural product. “This building system actually forms the majority of the buildings in Europe, and it's been around for 150 years in this extruded form,” Robyn claims.
What stands out about the system is its performance in passive heating
and cooling, high acoustic insulation, ventilation and moisture management. “The clayblocks are breathable with interior lime plaster, which is antiseptic, so as the air moves into the building, it's cleaning the air and we've got 100 percent natural indoor air quality,” says Robyn.
She adds most New Zealand homes will fall to around eight to 12 degrees overnight, whereas a Porotherm home retains the heat in winter and keeps cool in the summer. “It takes 12 hours for the heat and cool to move across that block, and it also moves moisture, so the blocks are breathing,” Robyn explains. “Our clients say living in these homes, it just doesn't go below 18 degrees without any heating.”
Clay is also the perfect material to create a quiet shelter – a naturally effective acoustic solution. “When you're inside it, it's quite cave-like. It just has a density around it and a peacefulness that is hard to describe until people get into it.”
By using an all-round material like this, you can reduce the need for all the extras we’ve come to rely on to make a home comfortable, like ventilation systems, dehumidifiers, heaters and air conditioning.
The best way to get a sense of everything Porotherm can do is at Stellaria’s first showhome, which opened this year on Swayne Road in Cambridge. There, they’ve used a mix of Stellaria clay brick cladding and breathable plaster with mineral paints by Resene Construction Systems on the exterior. Lime plaster is used to finish the walls inside, which has a venetian-like finish with an artisanal quality to it and is extremely smooth to touch – almost glass-like.
“The showhome is about all the products we import from Weinerberger and is the first in a medium-density development of duplex and detachable high-performance homes – we call it Swayne Village,” Robyn says. “These buildings will still be standing in 400 years time, which we don't see in New Zealand really.”
That’s what drives Chris and Robyn – the need for design to be backed by materials that will last the distance. “It's about knowing you've got an asset that not only has a better capital value but also is something that can be handed down. It's intergenerational, it's multigenerational. It's not a house, it's a forever home.”
Robyn says that in New Zealand, we should be following in Europe’s footsteps with products like Porotherm to avoid issues such as leaky homes and crying windows, which can lead to serious health issues. Because where you spend your time is as important to your health as what you put into your body. “We talk a lot about eating well, good water, sleeping well, reducing your pharmaceuticals, so [a healthy Porotherm home] is an extension of what people are trying to do with clean living.”
Stellaria is supplying a host of mid- to high-end projects from Mangawhai to Queenstown. But this product is for every home, despite the perception that building with it is going to be more expensive. The fact is, it’s comparable with a 140mm timber-frame build, at roughly $4,500-$5,500 per m2 to build.
“We're delivering something in which people will get much more for their money, and they should. Because it's the biggest emotional and financial investment,” Robyn says. “We not only believe in the integrity of the build, and the honesty in the building materials, we won't design in timber frame anymore.” Weinerberger warrants the design life of the Porotherm block at 150 years but the building will last well beyond that.
The plight to change the game is very much a family affair, too. All four of Chris and Robyn’s sons play a part in the businesses. Jonty heads up marketing for Stellaria, while Thomas lends his IT knowhow wherever it’s needed. Benjamin and Geordie recently finished building Geordie and wife Cassandra’s own Porotherm home in Taupō. Cassandra, of Cassandra Swan Interiors, also covers interior design projects like their showhome.
As with anything new or innovative, it takes time to build momentum and get people on board. Stellaria is in the process of setting up a showroom in the Home Ideas building and design showroom in Auckland, showcasing all eight of their Wienerberger products, including bricks, cladding, roof tiles and paving.
They are also working on an online resource called BlockBuild to connect people considering creating a home using Porotherm with architects, engineers and builders in their area, across New Zealand. Because Robyn and the team see each Porotherm build as its own promise. “The promise of performance, longevity, durability, and of good health,” she says. “That's why we love it, because we know that it's going to work. It's going to keep its promise.”