Martin Freney and his wife Zoe have embarked on the adventure of building an Earthship on their piece of land in the adelaide hills, to run as a B&B. This is to give people the experience of living in an Earthship, be it for a short time, and also for Martin to continue his Phd research on constant temperatures inside earth buildings.
This building has reached lock up stage, and finishing touches will happen in spring. Resently I was there for a month to help run a crew and interns on renders, bottle walls, hemp work and building the planter.
Martin and Zoe chose to have natural renders inside their Earthship, which which are both earth and lime renders.
Earth renders are a mix of clay, sand and straw (final layers can use wheat paste or casein instead of straw). To prepeare, this, we soaked onsite clay (which was very rich, orange beautiful subsoil, we were extremely lucky there!) in barrels mixed with an electric mixer (left).
For cob work (pack out of tires or bottle walls) this is mixed 1:3 with sand and 1 part straw. It is then foot stomped on a tarp as its heavy and sticky, pulling the ends of the tarp into the centre to help roll the mix over and over. Cob can be left in this form until needed, it doesnt harden or go off, but may need a little added water to suit.
Layers on the wall: The tires need to be packed out in stages, to bring the walls flat. Between each layer we wet the wall, and also brushed on a clay slip (very watered down clay slurry) for best adhesion. The next layer is only applied when the previous is dry. Then we started using trawls to apply the render, wood or steel, and we used a rough float or scratcher to keep the surface textured for the next coat. For the render we added clay 1:3 with fine blond plasterers sand, and half part fine chopped straw (run over with a lawn mower). Coats get thinner as you get toward your final layer, usually 3 coats are needed.
Niches can also be made with cob (right).
Lime render is a mixture of slaked lime (powered hydrated lime, soaked in water for 3 months or more), sand, and option of straw.
Mixing render: we used 1:2.5 lime to fine plasters sand. It needs to be mixed well, with an electric mixer and needs to be thick enough it sticks to your trowel if turned upside down. Skin and eyes need to be protected well at all times!
Application: We did one layer of render, on top of cement plaster (underside of vault, arch beam and bottle walls). We sprayed lime water on the wall first – this is the water sitting ontop of the slaking lime, or lime putty mixed 1:60 with water. We applied the render with steel trowls and floated with a sponge to blend the lines as it was setting fast. Strait lime plaster gave us a beautiful light shade, which we used on the ceiling and we will use sandstone colored oxide in other interior finishes where humidity will be a factor.
Lime can easily colored by oxides – Test patches on the buttress (above)
Thanks to everyone involved in this project, a wonderful example of a permitted ‘simple survival’ model Earthship in Australasia, and showing the possibility of an ‘owner builder’ designing and running the project on their own land. Pioneering work is very important, though often more time consuming and expensive, where we are all learning what to do and what not to, smoothing out design complications, testing materials and seeing just how many man hours go into the building. Thanks Martin and Zoe for hosting the community of builders and interns and sharing your project with us!
Part two, three and four will be on bottle wall construction, working with hemp as insulation, and building a grey water cell.
Words and images by Rosa Henderson. All questions and comments email email@example.com