Bristol Green House 2007	Gabion Foundations
• blog • plans • links • home To express an interest or book your place, email: build@bristol greenhouse.co.uk • Foundations • Tyre walls • Straw bale walls • I-beam roof • Living roof • Clay/Lime render • Insulation • Earthbags • Map	The ruins of a green house dating from the early 20th century on the site of the new 'green house'. These bricks will be reused in the foundations.
	Gabion foundations. This small building will be very heavy. The rammed earth wall and living roof will weigh over 50 tonnes between them. Solid foundations are therefore essential. Almost all buildings built since the early 20th century have concrete foundations. In the history of building this is a very short time. The making, transportation and mixing of concrete is highly energy dependent. Reducing the energy required to make this building is an underlying design parameter. Many straw bale buildings use car tyre pier foundations, a very simple method, but for this build, because it is cut into the hillside, that method was not appropriate. Instead I've opted for steel cages filled with the bricks from semi-derelict former greenhouses on the site and you can't get more locally sourced than that. Using what you have to hand is naturally the soundest method for eco-build. People tend to want off the peg solutions, but adapting to local conditions is the best eco-policy.
	I sourced them from Intermesh in Cheltenham. The life span is roughly a hundred years.
	I lined the cages with filter fabric so that any smaller pieces wouldn't fall out, but I certainly don't think this is essential as you are only supposed to use rubble or stones larger than the mesh.
	The cages tend to swell and bow as they are loaded. Filling neatly caused less buckling of the cages than roughly chucking chunks in. They are fairly imprecise building blocks. I used a thin layer of concrete on top of the gabions to even out the height differences so that the wall plate would be horizontal.