Rammed earth building grows in popularity as a more sustainable alternative
The growing concern around the energy and resource cost of construction materials like brick and cement has construction firms and architects looking to traditional materials for alternatives.
The rammed earth building technique, which requires only a combination of clay-rich soil, water, and a stabilizer, is thousands of years old and a predecessor to materials like adobe and cob.
Sustainable and low-cost in terms of energy and resources, rammed earth construction — in the form of traditional rammed earth and modern variants, like cement-stabilized rammed earth (CSRE) — is undergoing a modern reappraisal, leading construction firms to adopt the technique for new buildings.
These are three key benefits of rammed earth construction that are driving new interest in the technique.
1. Low Cost
The primary ingredient in rammed earth is damp soil, which is readily available at most build sites. If it’s not available, it can typically be purchased and brought on-site cheaply.
Other necessary materials — like the rammed earth framework, typically made of plywood, and stabilizers like cement — are often low-cost as well.
As a result, the material is often a good fit for project owners on a budget and rural communities which may struggle both with project funding and with the transportation of materials to remote building sites.
The unique texture of cured rammed earth may also help cut down on extra building costs.
Many designers, when working with rammed earth, opt for an interior without plaster or render covering the rammed earth walls. This creates internal wall surfaces with an interesting, unusual appearance and helps cut down on the total material costs for a structure.
Labor costs for rammed earth construction can also be quite low, as rammed earth construction is fairly straightforward. In some cases, it may be possible to build an entire structure with just one skilled worker who can coach others in the technique.
Cement-stabilized rammed earth walls, once cured, have compressive strength comparable to homes made of concrete, which offer high levels of strength and durability, as well as resistance to the elements.
One study examined how stabilized and unstabilized rammed earth walls would fare when exposed to the elements in a wet, continental environment in the southeast of France. The study found that after 20 years, only about 2 millimeters of the stabilized rammed earth walls had eroded away on average.
The unstabilized rammed earth walls performed surprisingly well also. After the 20-year study period, only 6.4 millimeters, or 1.6% of the wall’s thickness, had eroded away.
Recent experiments have also found that new types of exterior facades and structural reinforcement can make rammed earth even more durable.
For example, one research team has investigated the use of synthetic fiber additives, along with stabilizers like cement, to provide additional strength to rammed earth structures.
The growing popularity of the building technique may mean that similar discoveries could be made over the next few years — making rammed earth buildings even more durable and weather-resistant.
As consumer demand for sustainable building materials grows, construction companies have become increasingly invested in finding materials with a low carbon cost and that don’t rely on nonrenewable resources like petroleum.
The primary building material of rammed earth is soil, which can typically be harvested on-site, or cheaply transported from off-site as needed. This means a minimal need to transport materials to the site, which means less fuel is utilized in the overall building process.
The energy needed to produce rammed earth is also quite low, unlike a material such as brick. Typically, the only energy costs involved will be the transportation of soil to the site, costs associated with stabilizers like cement, and the energy needed to tamp down the damp soil into its framework.
Rammed earth does not have excellent insulating properties — but because the material is typically cheaper than alternatives like brick, it’s often possible to build thicker walls to make up for the lack of insulative properties.
This means building owners won’t need to spend more heating and cooling the building than they would with a structure made of more conventional materials. In some cases, a rammed earth structure may provide better insulation than a comparable structure of the same cost.
The most common stabilizer for rammed earth, cement, isn’t sustainable. However, the use of CSRE rather than cement alone is a major opportunity to reduce carbon emissions.
In 2014, for each ton of cement manufactured, around one-third of a ton of carbon dioxide was produced. Reducing the total amount of cement necessary for a job presents a major opportunity to reduce a project’s carbon footprint.
Why Construction Firms Are Looking to Rammed Earth
Rammed earth is a low-cost and sustainable building material that can result in highly durable and aesthetically interesting structures.
As demand for sustainable buildings grows — and research on rammed earth continues — the material is likely to become an even more appealing option for construction firms.
Emily Newton is the Editor-in-Chief of Revolutionized, a magazine exploring how innovations change our world. She has over 3 years’ experience writing articles in the industrial and tech sectors.