As part of the V&A’s Engineering Season Friday Late, we collaborated with The Stonemasonry Company to design and live build a torsional stone floor slab. Assembled by hand, the construction process is fast, clean, requires no temporary formwork and is completely demountable. The prototypical stone slab was developed as a low carbon alternative to a typical reinforced concrete slab, and as a construction methodology to deliver circular economy design solutions.
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 Webb Yates Engineers, we are of course interested in low energy innovation, 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!