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!
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
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.
Maybe i'll meet you on one of my rammed earth courses one day...
Oh, and one more thing,
Reduce - Re-use - Recycle, One Planet... TO THE MAX!
Man has always had a strong nesting instinct and, until relatively recently, the majority of people had to create their own homes. Professional builders only constructed churches, big public buildings, castles and mansions.
We have increasingly bought ready-made, off-the-peg houses, but the growth of the owner-builder movement has led to the rediscovery of the value of the use of natural resources, economic approaches, sustainability and self-help. What greater satisfaction can there be than to create your own nest?
Climate can determine the method most suitable for you. For example, you are unlikely to want to live in a bamboo house in a temperate climate, since big bamboo grows in the tropics and it also has next to no insulation. The most versatile material is strawbale, which can keep you warm in the cool and cool in the hot: its insulation qualities serve both equally well. As for wet weather, as long as your roof has large overhanging eaves and the walls are well-rendered and maintained, all materials will survive indefinitely.
Materials and Methods
A fifth of the world's homes are built from earth, mostly of pise (rammed earth) or adobe (mudbricks). In addition to these, there are several other methods of earth-building, as well as techniques that do not use mud, soil or clay. Most of the methods outlined have been in use for centuries and were precursors to today's bricks and concrete. Just because a building is constructed from natural materials does not mean there are any practical difficulties for the provision of electricity and plumbing. Usually a building permit or warrant from the local council will be required before the build starts. The design plan used to obtain the permit will include design of service provision. All the techniques that are described require solid footings and usually foundations, for which brick or concrete are the best materials.
Rammed earth or pise has been used all over the world in ancient and modern times. The great fortresses of the 10th Century in the Middle East are mostly of rammed earth construction and they stand remarkably unweathered today. Rammed earth is the best way of making walls from sandy soil by means of compression. Damp soil is packed solidly by ramming it into a strong rigid framework, or form, with vertical sides, placed in position over firm footings. It is made in courses: one section of wall at a time.
Some degree of carpentry skills are needed to build the formwork. The ramming itself is time-consuming and hard physical work, although mechanical rammers can be used. However, it is about twice as fast as mudbrick construction, partly because the wall is constructed in situ and partly because the earth is just damp and not sticky. Rammed earth will not shrink and develop cracks, although earth not sufficiently compacted will crumble away. It is possible to repair it, but it is best to avoid the problem in the first place. Ramming requires little water, which can be an important consideration in dry climates. On the other hand, ramming cannot be undertaken in wet weather, unless there is a roof already in place and the stockpile of earth is kept covered.
It is perhaps not surprising in these times of increased awareness of the impact that we have upon the earth, that there is a burgeoning desire and movement to construct our homes from materials that are from the earth; using methods that are simple, non-invasive and self-reliant. There are methods that suit every climate, every aspiration and every purse. They are all ancient methods, modified in the light of modern understanding of mechanics, engineering and safety. And what's more, in most western countries, the state will actually help you to build such a home.
Dream on and then act.