FAQs

some basics

 
   
 
 
 
   
         
Does rammed earth last?
Is rammed earth different from mud construction?
How energy efficient is rammed earth?
What about rain?
What does rammed earth cost?
What's the problem with cement?
Why rammed earth?

Does rammed earth last?

The oldest earth building remains are around 8,000 years old, but rammed earth has some notable long lasting examples. Most of the Great Wall of China is either rammed earth or has a large component of rammed earth as its basis. The Chinese found 2,000 years ago that in labour creation and resource management, earth could not be bettered. Also the Alhambra in Grenada in southern Spain is largely built using rammed earth, a mere 1,200 years old! But in terms of normal domestic use and in Northern European climate conditions, there are thousands of examples in England, France and Germany of at least 200 year old buildings, as much as 7 stories high.

Is rammed earth different from mud construction?

There are many forms of earth building, some which need more water than others. More water makes mud, and mud must dry before it can be used to build higher structures. Rammed earth is built using little water, so 3m to 4m high walls can be built in one day, that may be an important consideration where speed of building is an issue.

How energy efficient is rammed earth?

Rammed earth walls are about the same as brick or block in insulation value, i.e. not very good. But earth walls are thicker than conventional masonry, and so they can store more heat or more coolth which makes changes from day to night temperatures less dramatic. Thermal mass temperature storage means less active heating and cooling, which means less energy, and lower bills.

What about rain?

Like all other masonry rammed earth building lasts longer and better if it is kept dry. That means a damp proof course and a decent roof or cover. Earth can be sealed, painted, rendered, plastered, dry lined or sheathed just like any other masonry. Depending on the severity of the local conditions choices can be made to the level of finish. Often earth can be left without a covering layer, its colour and texture pleasant both indoors and out. Regulation will also mean that earth like other masonry products may need to be insulated, but it will always provide thermal mass, and that means comfortable levels of heat and cold.

What does rammed earth cost?

Rammed earth is comparable to conventional masonry, but there are key areas which can make a big difference to the cost. If soil is available on site then both material and transport costs are reduced. There are also economies of scale, bigger works have smaller set up costs. Costs for industrial materials are markedly reduced, leading to significant savings where foreign currency is short, i.e. developing economies.

What's the problem with cement?

To make a tonne of cement you have to produce a tonne and a quarter of carbon dioxide, the biggest greenhouse gas. ‘Rammed earth’ with cement in therefore has high levels of carbon dioxide emissions embedded in it. With 10% cement content its effectively concrete, and with all the clay taken out because its bad for the cement, IT IS CONCRETE.

Why rammed earth?

Earth building has the lowest amount of embodied energy of any masonry material. Cement production accounts for 10% of global CO2 emissions in the world! So finding other more environmental and sustainable ways of meeting ever increasing demand for roofs over our heads is vital. Earth can carry large loads, but cannot make sky scrapers, so keep cement for sky scrapers and earth for other housing, schools, clinic or business uses.

 

 

Here rammed earth made from the waste products of brick production retains soil brought in for the next batch of brick making at the Fambidzanai Permaculture Centre close to Harare, Zimbabwe

Rammed earth is earth which is moist when put into a mould and then compacted or rammed in place. Here a mechanical rammer is being used.

 
 

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