An introduction to Rammed Earth by Michael Thompson Rammed-Earth.Org
When I first stumbled upon rammed earth, I was no eco warrior. The most I ever did to save the planet was recycle my empty beer cans. But building with earth turns out to be a very sustainable thing to do...
The rammed earth building method is a very clean process that produces a smooth finish and avoids the heavy cost to the environment of building with bricks and blocks; but best of all, It's dirt cheap!
Using rammed earth involves a process of compressing a mixture of damp earth that has suitable proportions of sand, gravel and clay into an externally supported former that moulds the shape of a wall section creating a solid block of earth. Traditional stabilisers such as lime or even animal blood can be used to stabilise the material, but cement has been the stabiliser of choice for modern times.
The use of cement is contentious as its manufacture creates ten percent of manmade carbon emissions. However, this may be substantially offset by the partial substitution of cement with alternatives such as ground granulated blast furnace slag or by using hydrated lime.
Formwork is set up to create the desired shape of the section of wall and damp subsoil is placed inside the former to a depth of around 100 to 150mm. A pneumatically powered backfill tamper - something like a hand-held pogo stick with a flat plate on the bottom (or alternatively a manual tamper) is then used to compact the material to around fifty percent of its original volume. Further layers of material are added and the process is repeated until the wall has reached the required height.
A rammed earth wall is so solid that the former can be removed immediately. However it will require a number of warm dry days after construction to dry and harden. The structure can take up to two years to cure completely and the more it cures the stronger the structure becomes. When the process is complete, it is much like constructing a handmade wall of solid rock.
In modern variations of the method, rammed earth walls are constructed on top of conventional footings or a reinforced concrete base. To add interest to the structure, some builders add coloured oxides or items such as bottles or pieces of timber.
Because rammed earth structures utilise locally available materials, they typically have a low embodied energy rating and generate very little waste. Earth used for building is a widely available resource and harvesting it for use in construction has minimal environmental impact.
Insects won't infest rammed earth and if unstabilised the material is reusable and biodegradable.
Rammed earth is not only an economically viable construction technique; it also results in a visually pleasing end product.
To find out more please visit my Web site and browse through all the photos and videos or even buy my recently published DIY Rammed Earth Manual.
Maybe i'll meet you on one of my rammed earth courses one day...
Michael RammedEarthOrg
Oh, and one more thing,
Reduce - Re-use - Recycle, One Planet... TO THE MAX!
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