Rammed Earth in the Tropic

by Ar. Jason Lee Shiuh Liang (for dissertation 2009)

In a 2009 dissertation for the Degree of Master of Architecture, we analysed Rammed Earth construction techniques and its viability for use in Singapore. Rammed earth is a traditional method of construction using compressed unbaked earth – usually to construct walls – that has a long history as far back as 500 B.C. Similar to the use of concrete, temporary formwork is used to hold loose and moist earth, that is them compacted with a mechanical ramming equipment and left to dry, layer by layer. This gives it a natural and distinctive layered appearance, similar to stratified soil.

The benefits of rammed earth are significant for the environment. It has exceptionally low embodied energy – it requires little to no processing and thus near zero energy consumption and emissions compared to commonly used concrete and steel – and using earth from or within the vicinity of the construction site means minimal transportation emissions. Furthermore, it is a highly sustainable material that can be easily broken down and reintegrated into the land at the end of the building’s life. In most cases where the soil onsite is unsuitable, additives such as cement, lime, and pozzolanas can be incorporated in small quantities to stabilize the soil.

Its advantages also extend beyond sustainability. Rammed earth buildings have shown to be able to regulate heat and humidity better than concrete, providing optimal comfort for inhabitants. Cost is also significantly reduced as the material can be naturally and locally sourced where possible hence reducing transportation and processing need.

However, there is hesitation in using rammed earth as a construction material, stemming from the idea that it is unsuitable for use in tropical climates because of the high humidity and rainfall, and the prejudice that earth is a material used in and associated with underdeveloped regions. This dissertation also aims to dispel these concerns & prejudice.

In researching rammed earth buildings, we analysed 3 existing buildings that extensively featured rammed earth construction.

The Lam Plai Mat community centre in Buriram Province in Thailand features rammed earth flooring and load-bearing columns supporting a curved roof, creating a layout that allowed for natural ventilation. Designed by Akitek Tenggara and completed in 2007, it was built by the local community using recycled metal barrels as formwork constructed and soil excavated onsite. The extensive roof overhangs and raised floor of the building protect the rammed earth columns from the tropical environment. The cavity left behind by the excavated soil was ingeniously turned into a pond that surrounds the centre.

Designed by Kevin Low and completed in 2004, the Mud Houses is part of the Sekeping Serendah private resort in Selangor, Malaysia. The 2 mud houses feature rammed earth walls that were constructed with onsite soil by builders with little rammed earth experience. The 2 builders mixed the soil using their own judgement with no scientific testing. Because the walls were used as infills and partitions and were not load bearing, they required minimal protection. After years of exposure to the elements, they were still standing strong and had been slightly weathered, giving them a natural finish.

Lastly, the Joanna House in Victoria, Australia designed by Nicholas Burns and completed in 2007 easily dispels the prejudiced that rammed earth construction does not belong in the modern architecture scene of developed regions. Its use of rammed earth walls interfaced with concrete and steel gives it a modern finish that still blends well into the natural environment. The use of well-engineered soil excavated from the vicinity is estimated to have saved up to $30,000. Roof overhangs, water-based coatings and rammed earth’s inherent durability and stability has allowed the Joanna House to withstand driving rains of up to 80 km/h. There have also been no complications with the integration of services into the load-bearing rammed earth walls.

The analysis of existing research and these 3 buildings led us to conceive certain proposals – detailed extensively in the dissertation – that would integrate rammed earth construction into Singapore’s architectural landscape. Below are some of the key analysis and recommendations.

Analysis of soil in Singapore has shown that up to 75% of it is suitable for rammed earth construction and can be classified as lateritic – making it highly resistant to weathering. This can be further stabilized by adding materials such as sand and gravel of additives like lime. Soil is also easily accessible through excavation onsite. We further propose to tap into the current soil reserves that were excavated for underground projects such as expressways, train tunnels and underground service lines.

In designing rammed earth buildings in Singapore, we must consider that rammed earth is more suited to low-rise buildings and should be used for areas that require more enclosure and possess mechanical ventilation. Furthermore, protection from rain and shading from the sun is crucial for durability and optimal building temperature, respectively. This can be easily achieved by incorporating good hat & good shoe elements – roof overhangs and raised foundation and footing – and shielding elements in the building’s design. Shielding can be in the form of shading devices, vegetation, trellises and claddings.

Other design considerations include walls that turn at regular intervals or fins incorporated into walls to increase self-support and stability of walls. Rammed earth flooring can also be suspended to allow for ventilation under the floor or in contact with the ground to increase its thermal regulation properties.

To increase productivity, Singapore can tap into and further R&D in advanced rammed earth technology such as prefabricated rammed earth elements and Pneumatically Impacted Stabilised Earth (PISE) – which is significantly faster than traditional ramming methods and allows for easier service integration.

Taking up these proposals and considerations can allow the successful integration of rammed earth buildings into Singapore’s landscape. This would aid our pursuit towards sustainable development and introduce a new aesthetic into our urban environment.