Down to earth
How do you protect a priceless collection of irreplaceable items?
To preserve 1.4 million botanical specimens at the National Herbarium NSW, a high-performance material was needed. The final design, six rammed earth vaults that appear to rise from the very ground below them, used one of the world’s most ancient construction techniques as an innovative solution to a strict and fascinating brief.
The Herbarium is the first public building in Australia to feature rammed earth walls as a certified fire rated, structural wall system.
The six bespoke vaults, designed for 100 years of life, had to meet strict compliance standards to protect the priceless collection from bushfires, extreme weather events and to maintain strict climatic conditions.
In keeping with the scope of the collection, an immense 2,100 tonnes of rammed earth was compacted into the towering vaults, all protected by a hovering fly roof.
The sweeping fly roof hovers over the six vaults.
The result is a timeless design, deeply rooted to the site around it and paying tribute to the land’s historical significance as the meeting place Yandel’ora or ‘land of peace between peoples’. Once in a generation, the site hosted hundreds of thousands of First Nations people from south eastern Australia, who left their weapons behind in order to settle disputes peacefully.
The earth used for the build, sourced just 34 kilometres from the site, is a nod to the site’s geographical importance as well as a sustainable solution, requiring little to no carbon to produce and mixed with minimal cement.
Rammed earth was chosen for its character and its protective properties.
The rammed earth was sourced locally, exuding a profound sense of belonging to the land.
The largest collection of its kind in the southern hemisphere, the Herbarium includes specimens from New Zealand dating back to 1769, plus 800 specimens collected during Captain Cook’s voyage in 1770. This is a time capsule of pre-colonised landscapes, and not all pretty: poisonous plants used by Indigenous people to cause pain and even muteness are featured, as a are mind-altering substances and an ancient variant of nicotine, although source locations are kept a strict secret to prevent poaching.
Strict temperature requirements were a major element of the brief, put in place to protect the vast collection and to stop the collection from expanding.
To prevent insects from breeding, the temperature inside the vaults was required to be kept at 16° Celsius and 50 percent humidity.
Fire resistance was another major requirement for vaults, with a four-hour fire rating an incredibly stringent condition in the brief. The earth was subjected to four hours of flame exposure and passed the test with flying colours.
The material being tested for fire resistance.
Lead designer Luke Johnson also highlights the unquantifiable qualities of a material that has been used for millennia.
“The rammed earth is textured and stratified like geological formations. It exudes a truly timeless quality,” he says.
