As part of the V&A’s Engineering Season Friday Late, Interrobang collaborated with The Stonemasonry Company to prototype a torsional stone floor slab. By supporting the array of stone slabs along their four sides and holding them down at the four corners, the floor structure is extremely thin. As was demonstrated by the live build at the museum, the construction methodology is fast, clean, requires no formwork, and can be built up from handleable elements.
Unlike vaulted stone structures that work by ensuring the stone is working only in compression, or post-tensioned stone that utilises steel tendons to work in tension in concert with stone in compression, the stone tile floor is both perfectly level and includes no steel reinforcement. This is achieved by clipping very thin stone tiles together at their corners and holding the structure along all four sides, here allowing 3m to be spanned with just 40mm depth, less than half the thickness that would be required by a reinforced concrete slab doing the same job. Compared with reinforced concrete, the stone tile floor is less than half the embodied energy and less than a quarter of the embodied carbon.
At Interrobang, we’re interested in low energy innovation of course, but beyond this we’re keen to demonstrate that not all contemporary innovation is about exploiting digital fabrication or creating wild new forms. Looking forward, as environmental concerns increase and energy prices rise, stone will become a more viable competitor to concrete. More rigorous testing of stone will therefore become more widespread. Timber is currently graded to ascertain the properties of a specific piece of timber. While it is possible to do this with stone (via load testing or x-ray etc) it is not commonly done. This means that we’re not asking stone to work as hard as it can and so over-structuring and wasting material. There’s enormous potential to bring technology to bear to industrialise local stone extraction. As a natural material, the properties of an individual piece of stone vary, and this variability manifests as excessive safety factors. By better automating the way stone is extracted, cut, and graded, we will be able to use it more efficiently and much more broadly. The goal is that in the future, steel and concrete are much less dominant in the construction industry. If stone can step up to become a much more viable alternative, we can dramatically reduce the carbon footprint of construction: back to the stone age for a low carbon future!