Research reveals that having just the right amount of water is the key to maximising the strength of rammed earth

The secret to successful sandcastle construction could help revive an ancient eco-friendly building technique, according to researchers.

Experts at Durham's School of Engineering led a study into the strength of rammed earth, which is growing in popularity as a sustainable building method.

In the same way that a sandcastle requires just a little water to stand strong, the Durham engineers found that the strength of rammed earth was heavily dependent on its water content.

Rammed earth is a manufactured material made up of sand, gravel and clay, which is moistened and then compacted between forms to build walls. It was developed in ancient China around 2,000 years before Christ.

Buckets and spade
Having the right amount of water is the key to both sandcastle building and rammed earth construction

There is increasing interest in using the technique as it may help reduce reliance on cement in building materials - cement production being responsible for 5% of man's CO2 output. Rammed earth materials can often also be sourced locally, reducing transport needs.

It is hoped the findings could also aid the conservation of ancient rammed earth buildings by putting methods in place to protect against too much water entering a structure, which would reduce its strength.

Paul Jaquin, a researcher on the project, now works for engineering consultancy Ramboll UK on new earth building projects around the world, and is using this research to better engineer buildings.

Research project leader Dr Charles Augarde, of Durham University's School of Engineering, said: “We know that rammed earth can stand the test of time but the source of its strength has not been understood properly to date.

“Without this understanding we cannot effectively conserve old rammed earth or make economic designs for new build.”

He added: “By understanding more about this we can begin to look at the implications for using rammed earth as a green material in the design of new buildings and in the conservation of ancient buildings that were constructed using the technique.”