Earth Building: Rammed Earth – Steffen Welsch, Steffen Welsch Architects

Are you looking for a unique sustainable material with a low carbon footprint?

In today's episode, we move on to our next sustainable design theme, Earth Building, and investigate rammed earth construction. Architect Steffen Welsch, director of Steffen Welsch Architects, shares the story behind his Butterfly House project, located on an off-grid site in Rutherglen in the hot, dry summer and cool winter climate of north-eastern Victoria.

Today we'll learn about the process, benefits and costs of using rammed earth construction and a wealth of insights and practical information drawn from Steffen's extensive experience.

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MORE INFORMATION

Find everything you need on the Renovation Collaborative website.

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• PODCAST Key points summary, timestamps and resource links
• FREE RESOURCES Transcript edited into clear Q&A.
• CPD Australian architects can find more information on CPD, and
• COURSES Eleven easy to read courses demystifying the entire home design and construction process.

KEY POINTS SUMMARY

1. Rammed earth was chosen for this project because it suits the local continental climate. It optimises energy efficiency by absorbing and releasing heat slowly throughout the day, stabilising internal temperatures. This means it helps maintain a moderate temperature range inside the house by absorbing heat in summer to take the edge off those high temperatures and releasing heat slowly in winter to take the edge off low temperatures.

2. The soil used for rammed earth must be laboratory tested to ensure it is structurally suitable. In Steffen's experience in regional Victoria, there are usually quarries with appropriate soil located within a reasonable distance from most sites. A rammed earth contractor can assist with this process.

3. The rammed earth construction process is relatively simple and dates back over 10,000 years. Plywood formwork boxes are constructed and a rammed earth mix, of dirt, cement, water and potentially other admixtures is poured in and compacted with specialised equipment. At the time the Butterfly House was constructed, rammed earth walls comprised a single solid wall with a thickness of around 500mm. Now, rammed earth walls must include insulation. Their current composition involves an internal layer of rammed earth, a core of thermal insulation and an outer layer of rammed earth, resulting in an overall wall thickness of around 450mm. Alternatively, rammed earth can be constructed as a 200mm thick reverse brick veneer wall.

4. Rammed Earth offers numerous benefits, including thermal mass to stabilise internal temperatures, excellent acoustic qualities, high flame resistance, low embodied carbon and durability and a long lifespan,...