I have spent time over the last couple of months building a vault out of un-stabilised in-situ rammed earth. Without known precedent, it is believed to be a world first. Although there is a pre-cast example built in Austria by students under the supervision of Martin Rauch, there are significant challenges relating to the in-situ construction process that I was testing. The vault is a 1:5 mock-up of part of my Final Major Project proposal for sustainable Greenbelt Development outside Edinburgh.
The full size vault would be 11 metres wide and 9.5 metres tall at its highest point and extends 20 metres to form an open air hall aimed to encourage a respect for the earth that we rely on to grow food and that can also provide another of our basic needs: shelter. It would also be occasionally used for events relating to the small scale, sustainable farm work that takes place on the rest of the site.
The principle behind the rammed earth vault lies in the structural properties of rammed earth, which has significant compressive strength but cannot withstand tensile stress. When flipped to form an arch, a catenary curve – following the path of a chain as it hangs in tension from two fixed points – creates a structure that is entirely in compression. Whilst the structural principle is ancient and simple, the construction implications of angled ramming and formwork design were unable to be proven possible until the removal of the formwork. The revealing of the finished vault on the 16th of December was witnessed by CAT students from across the REBE, SA and Prof Dip courses.
I would like to put out a huge thank you to the staff and long list of students who helped me and to Rowland Keable, whose advice on the removal of formwork (which can be a risky procedure) was invaluable.
Here is a video showing the formwork being removed:
This blog is by Tasha Aitken, a final year student on the Professional Diploma in Architecture: Advanced Environmental and Energy Studies course; the Part II Architecture course at CAT.