Ancient building technique may help future designs to be more eco-friendly

23:24 June 4, 2009 PDT

Walls made from rammed earth may hold the key to more eco-friendly housing design in the future

Every child learns early on that moist sand is the key to building a sturdy sandcastle. Now researchers at Durham University have studied this principle so it can be better applied to an ancient eco-friendly building technique of using rammed earth.

Rammed earth is a manufactured building material made up of sand, gravel and clay, which are moistened and compacted between two forms – or molds – where the mixture is allowed to set as a wall.

It was developed in ancient China about 2,000 BC, but it has been enjoying a resurgence in popularity as a sustainable building method in recent years, as it reduces the need for lumber and the forms holding the rammed earth in place can be reused.

The researchers, led by experts at Durham's School of Engineering found that the strength of rammed earth was heavily dependent on its water content. They also found that rammed earth walls, in a suitable climate, dried without losing all their water. The small amount of water that remained provided considerable strength over time.

The team believes that further study will help reduce the reliance on cement in building materials, which is responsible for 5 percent of man-made carbon output, and in doing so, cut carbon emissions. The environmental impact of rammed earth is further minimized since rammed earth materials are commonly sourced locally, which means it doesn't need to be transported long distances.

According to the researchers, their work may help the future design of buildings using rammed earth, and as the link between strength and water content becomes clearer, conserve ancient rammed earth buildings by putting methods in place to protect them against too much water entering a structure, which weakens rather than strengthens it.

The research from the Durham University team was published in Geotechnique.

Darren Quick

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User Comments (4)

This is called "taipa-de-pilÃ£o" here in Brazil. There are many houses built with rammed earth here, and they last for hundreds of years with low maintenance. I participated in the building of a house using a different technique used by southamerican indians and tried out some other. Unfortunatly, people don't use this anymore and keep on living in shacks when they could have a healthy environment to live in. I'm intending to build a house with various techniques to demonstrate this to less fortunate people and teach them to build their own houses with very low cost.

For example, a finishing can be made with newspaper dissolved in water and mixed with clay in a almost liquid solution. Applying it many times creates a good finishing for interiors, for exterior walls it must be made waterproof. I used this to build a wood stove and it worked very well. For the inside of the stove I used a mixture of wood ashes and clay in the same manner. This creates a fireproof finishing that reflects the heat, improving the efficiency of the stove. It is not very strong, but it's maintenance is easy. Other building material involve straw, horse manure, and so on. We should use such materials, they are green, carbon neutral and won't contaminate the environment. And, best of all, they can be found anywhere.

walther.grube

- June 5, 2009 @ 02:06 pm PDT

I at one time thought it would be nice to build a partially-subturanian house like this but condemned the idea because of one small concern, earthquakes. I have not heard any mention anywhere on how such a building would perform under tremors. My guess is not nearly as well as a concrete block wall with rebar reinforcement.

Matt Fletcher

- June 6, 2009 @ 08:06 am PDT

There is no reason why re enforcement techniques using steel can't be used with rammed earth.

Also geometric design could be employed which would create an extremely strong structure.

Not only that but walls could be pre made on site, and then erected using modular design...

Un re enforced concrete is also subject to earthquake damage. That is why all concrete structures have steel re enforcing.

Having said that, we are at risk of being buried in various forms of plastic which could be utilised for dwelling structures.

As my grandmother always used to say, "where do you think away is? You can't throw something away, you throw it somewhere else."

We are fast running out of the "somewhere else".

Facebook User

- June 19, 2009 @ 01:06 am PDT

rammed earth doesn't have very good insulation, and requires additional insulation for severe climates. It does have thermal mass however.

Facebook User

- June 29, 2009 @ 07:06 pm PDT