I came across this video on youtube and had to know more about this project.
When and where did you first hear of rammed earth?
I first heard about it in January this year, it was used as an internal feature wall on a "Build an Eco House in 7 days" TV programme here in the UK. The house itself was primarily timber frame and straw bale, but this feature wall was amazing... I had to have a go!
What was the first rammed earth building you ever visited?
The first rammed earth building I visited was my own! I live in the UK, the chances of you being able to visit a rammed earth building are slim... The Eden Project has a rammed earth visitor centre but that's 6 hours drive for me.
What motivated you to build with rammed earth and not another building method?
At first it was the appearance of the finished walls, then when I realised it was dirt cheap it became the cost, now having single handedly rammed the walls I would say it's the connection with the earth as a building material.. it can be quite a humbling experience at times.
Is there rebar ( steel re-inforcement) in the walls?
I looked at how the Indian communities contructed single storey buildings and decided not to bother with any rebars. I have however added an additional "bond beam" between the roof joist to tie the roof joists together from each side of the 5 degree flat roof.
How did you come up with your soil mixture?
I used a "Soil Triangle Diagram" that I found on the internet, analized my own soil from the footing excavation by using a coffee jar full of water, then you add your soil sample, shake for one minute and the leave on a flat surface for 24 hours, you can then see how the soil has settled. I needed more clay silts so I imported 13 tons of sub soil from 6 miles away near the coast. I then used my invention "Sid the Soil Sieve" to grade the earth down to 12mm 0r 1/2 inch Once blended with 5%-8% cement they appeared to make the perfect soil for ramming.
Any idea of your material costs?
This is a 66m2 building with a maximum height of 2.8m, the budget for the raised footings, additional earth, roof structure and the soon to be planted out Green Roof is a mere £2,700.00 and I'm on track to achieve this budget. Notice that I am building a shed, not a dwelling, and so this was a project on a very tight budget... Pound Zero as I call it. I am a Joiner by trade and work within the building industry, so I see a lot of waste and over-engineering, this shed is just a single story building, and so the need to spend a lot of time and money was not required in my opinion... time will tell if it stands the test of time!
How long did it take to ram the walls?
It takes me about 3 hours to ram each section, each coffin former hold 200mm X 2000mm X 500mm of rammed earth so based on that you could say that it would take 15 hours to ram 1 cubic meter by hand.My Eco-shed has 60m2 of walls so it should take me about 180 hours to ram. But you can double that twice over when you add in the sieving and mixing of the earth, setting up the formers and fighting the elements etc.
Is there any insulation?
I didn't bother with the expense and extra work of insulation, the walls are too thin for starters (only 200mm or 8" thick) and this building is mainly going to be used as a garden kitchen and storage area. Also where I am the weather is pretty good, we have the lowest rainfall in the UK and the winters are mild by comparison the the rest of the country.
What would you do differently next time?
After spending three months researching and many hours designing this building to the last detail... even making scale models, I think that I have got this pretty much nailed down, maybe in a year or so I will see some areas of improvement, but so far I am more than happy with the results. I myself have found the whole experience has made me think a lot about rammed earth construction, so much so that I have decided to write an eBook information manual on building Rammed Earth Sheds this winter... watch this space for more info.