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Invasive Weed & Mayonnaise Strawbale Render The render applied to strawbale walls can make all the difference between a finish that looks good and keeps water out, and failure. Ben and Lena share some innovative techniques originally developed in Denmark. Mylor, South Australia
We’ve been interested in strawbale building for almost a decade now, and have been living in our tiny house, which we call ‘The Hut’ since 2005, even though we’re still building it (sound familiar owner-builders?). When we met Tom Rijven and his partner, Sophie Guyot, through mutual friends in Denmark (the international strawbale community is amazing), we immediately started talking about the virtues of strawbale building — ideal climate control due to its fantastic insulating properties and walls that breathe, very low embodied energy, ease of construction and so on and so on. We also realised that while we know a lot about our way of strawbale construction, Tom has a very different approach, one we wanted to try out. Together we decided to hold a rendering workshop to finish the outside of The Hut. These 12 photographs will give you a taste of the final two coats in Tom’s three-coat rendering system (we had already partially rendered our exterior walls before we met Tom, and had to adapt his system). First we made some body coat, then we prepared render stops, applied the body coat, and made and applied a finish coat to a small section of wall we had body coated prior to the workshop. 1: The body coat Tom’s recipe for the body coat is surprisingly clay rich, and ideally needs to be made one to two days (depending on the climate) prior to use to allow it to ferment. Fermentation is crucial as the resulting lengthening of glucose molecules makes it stronger and more waterproof. Our most invasive weed, Montpellier Broom, said ‘ideal body coat material’ to Tom, as once mulched it has millions of micro-fibres and ferments quickly. Due to the existing sandy render on our walls, we adjusted the sand to subsoil ratio in our body coat in order to get it to adhere properly. Body coat recipe
A word of warning: in earth building, materials are unique, not standardised like cement, so it’s crucial that you do your own tests and personalise any recipes. Also make sure your supplier doesn’t change sand types mid-construction (like ours did!). 2: Render stops and protection from water These standard concrete pavers have been glued to the existing foundations (old car tyres rammed with earth) using a very dry clay slip. They provide a good render stop that’s well above finished ground level, an exterior ‘skirting board’, and a clean edge to pave to (anyone want to run a paving workshop for us?!) 3 & 4: Before and after some window detailing. To create the desired form, Tom’s keen eye could see that the existing form needed reshaping, which we did with a claw hammer used like a pick-axe. Then the whole area was thoroughly wet down, a clay slip glue was applied, followed by the body coat (in places up to 15 cm thick) to achieve an elegant form (our existing render can still be seen in photo 4). Ben and Lena go on to discuss the following steps in the rendering system:
The English version of ‘Between Earth and Straw’, published by Goutte DE Sables, is due in June this year. top | FAQ | Resources | Strawbale home | Back to EG |
