Exploring the pros and cons of the rammed earth building method

As the world increasingly seeks sustainable and eco-friendly construction methods, the ancient technique of rammed earth building has re-emerged as a viable option.  

Rammed earth construction involves compacting mixed earth, gravel, sand and clay within a framework. Paul Marias, an architect at Simply Sustainable and a pioneer in this environmentally friendly technique, talks to Estate Living about why it’s becoming more popular.  

The pros of rammed earth building 

The rammed earth method is eco-friendly and efficient. This is because there is typically no manufacturing process involved as builders make use of locally available earth. In a world where resources are scarce, this is a big advantage.  

‘It’s environmentally friendly unless cement is used to stabilise the earth. I use lime stabilisation mostly with bitumen stabilisation used occasionally. Cement is responsible for around 8% of global CO2 emissions and it requires the use of clean sand which is also in short supply globally and an environmental disaster in Africa where rivers are mined for the sand which in nature acts as a filter for the river. This also creates catastrophic downstream floods,’ says Marais.  

As most of the building work is done by hand, there’s also less of a need for construction equipment, which again can reduce the cost.  This reduces the need for transporting building material, which in turn reduces carbon emissions. It also minimises waste production and promotes recycling as developers make use of the building site earth.  

There are health benefits to this method too. ‘Some clients have medical conditions and request this building technique as they don’t want paint to be used. There are no paints or plasters required,’ explains Marais.  

Using the rammed earth method reduces energy consumption as well. ‘It has fantastic thermal properties except where cement stabilisation is used as it can cool hot air effectively and warm cool air, creating indoor thermal comfort,’ says Marais.   

Rammed earth structures are also renowned for their durability and resistance to fire, which makes it a good method to adopt in regions prone to wildfires.  

The cons of using rammed earth building 

There are some drawbacks to this method. The first is that it requires specialised knowledge and skills. Therefore, finding the right people for the job can be difficult, compared to using conventional methods so the process to completion could be slower. This could ramp up the costs.  

Some experts suggest that rammed earth designs could also be vulnerable to water damage. If there’s prolonged exposure to rain there could be damage to walls through erosion, cracks and this could result in the structure of the building being compromised.  

This is why it’s crucial to hire the right experts who will choose the right sites, ensure quality craftsmanship and that the appropriate water management systems are put in place to reduce the risk of water damage.

A worldwide method 

Despite its potential vulnerability to water, buildings constructed from this method have existed in wet areas like the UK and Northern Europe for centuries. There are also rammed earth structures in Hanoi, Vietnam and Czech firm Formafatal recently used this method to construct two modern villas in Costa Rica.  

Marais has an impressive portfolio in Africa using this method. He recently completed a lodge in Elephant Point in the greater Kruger Park, which was featured in The Architects Digest’s Europe Edition last year. Back in 2016 he won the AfriSam-SAIA Award for Sustainable Architecture + Innovation after one of his clients submitted his design for “Otto Cottage”. It’s located in Maun, Botswana, and was built using natural materials from the surroundings.  

The Maun home is now advertised on Airbnb and was voted one of the top ten Airbnb’s globally. It’s been featured in lots of magazines that have highlighted the use of rammed earth building. ‘It’s very marketable if you say you have a lodge that is built with eco-friendly methods,’ adds Marais.  

An ongoing appeal 

It’s undeniable that Marais is a fan of this technique and proudly admits to training others in this lifelong passion. ‘It’s becoming more popular. I believe I was the founder of the revival in Southern Africa and almost all other practitioners learnt from me at some stage.’ 

But will it be a method used to build residential estates? Marais believes it’s possible as it’s become more widely accepted with banks no longer hesitating to finance such builds. ‘It’s now accepted as a standard way of building. Five to six years ago we would’ve had a lot of meetings and done a lot of work to convince them to finance a project. Now we’re finding approval is much easier.’ 

The only remaining stumbling blocks are the costs and the lack of skilled people that can create such a build. Marias says: ‘There’s about three to four people that can do it in South Africa. We’re quite small and not part of big established companies but when we build to scale it becomes cheaper. I have a project in Botswana where I’m doing 30 units and doing it for half the price of a brick-and-mortar unit. But when you do just one house it’s generally more expensive. I believe we’re close to constructing residential estates using this method.’