Rammed earth is an ancient sustainable construction material, made by compacting soil between removable formwork to form a monolithic wall. Long sections of the Great Wall of China, and famous buildings such as the Alhambra in Granada, and the Potala Palace in Lhasa are built in rammed earth.Recently rammed earth has become popular as a sustainable construction material. There are numerous benefits to the environment in using rammed earth compared to more modern alternatives of concrete and steel.
CO2 emissions
Using rammed earth as a construction material greatly reduces the amount of CO2 released during the construction of the building.
The manufacture of cement requires the burning of limestone and produces CO2 as a waste product. Around 10% of global CO2 emissions are from the cement industry [1].
In using soil taken directly from the site, there is no transport requirement, directly reducing CO2 emissions and taking vehicles off the road.
1. The Guardian A cracking alternative to cement May 2006
Article
Thermal performance
The high thermal mass of rammed earth walls mean they act to naturally regualate the internal temperature of a building. If a rammed earth wall is designed into the heating system of a structure, the energy required to both heat and cool the building can be greatly reduced, which further reduces the CO2 emissions of the building.
Rammed earth naturally regulates the internal relative humidity of the building, producing an improved air quality. This contrasts greatly with air conditioning systems, which act to dry the air in a building and contribute to harsh working and living environment.
Treloar et al 2000. Environmental assessment of rammed earth construction systems Structural Survey Article
Taylor & Luther 2003. Evaluating rammed earth walls: a case study Solar energy Article
Structural performance
Rammed earth is perfectly able to act as load bearing members within a structural system. We have particular expertise in the structural performance of rammed earth and have developed novel testing methods to aid understanding of the fundamental mechanisms governing the behaviour of rammed earth. The strength of dry, unstabilised rammed earth is close to 1MPa, but both the strength and stiffness of the material reduce greatly with increasing water content, and thus the building must be well designed in order to maximise the structural potential of the rammed earth.
Embodied Energy
The inherent recycleablility of rammed earth, and the reduction in CO2 emissions during the lifetime of the structure, the high thermal mass and thus low operating costs all mean that rammed earth has a much lower embodied energy than comparable building materials.
Feasibility
Rammed earth complies with UK Building Regulations for insulation, strength, water resistance, fire and acoustics. We are able to provide:
Soil evaluation and mix design
Not all soils are suitable for use as rammed earth. We have expertise in blending the right mix backed up with a technical understanding of the fundamental mechanics. The soil must be compacted at a particular water content to ensure optimum compaction, and this water content should be predetermined before construction begins.
Sample construction and testing
Many projects require samples and walls to be constructed and tested to failure prior to full scale construction.
Design advice
Structural design of rammed earth buildings is usually very simple, with walls acting in compression, but detailing is important to ensure the rammed earth is used to its maximum potential.
Downton, P. 2005 Rammed earth. Your Home Technical Manual, Australia’s guide to environmentally sustainable homes. Canberra Article
Example buildings
A small number of rammed earth structures have recently been constructed in the UK.
A rammed earth wall in the centre of a sustainable office complex on the outskirts of Durham. The rammed earth wall acts as a feature in the centre of the building, and is coupled with rainwater recycling and other ecological features to make this an example sustainable building.
Pines Calyx is a conference venue 90 minutes from London and aims to provide a sustainable and natural environment for delegates. Built from rammed chalk, the site claims to be one of the most sustainable buildings in Europe.
The Genesis Centre is the sustainable construction resource and learning centre for the South West of England. The centre aims to demonstrate that traditional construction materials and methods can work in harmony with recycled waste and modern materials and techniques. The Centre runs Continuing professional development courses for construction professionals and those involved in self build and sustainable construction projects.
WISE Project Centre for Alternative Technology
The Centre for Alternative Technology, Wales has recently completed the rammed earth walls of the Wales Institute for Sustainable Education. The 7.2m high rammed earth walls of the lecture theatre are the tallest in the UK, and are an impressive feature of the new building. The soil mix was sourced locally from a quarry waste material, and compacted in curved formwork.
The visitor centre at the Eden project, Cornwall is constructed in rammed earth. Eden aimed to provide a natural and sustainable building in rammed earth, in addition to the iconic domes at the site.
