Rammed earth and bamboo
- In Nepal, a sustainable design technique called ‘rammed earth’ design is gaining popularity among artisans and architecture enthusiasts, but the design is more than just an environmental fad: it may end up cheaper for homeowners in the long-term, too
Jun 20, 2014-
Narayan Acharya is a beekeeper, organic farmer, and builder. A year ago, he purchased a plot of land in Godavari and set to work building one of Kathmandu’s most distinctive homes—constructed largely from rammed earth and bamboo.
The idea was sparked by a compressed block building Acharya saw on a trip to northern India. Acharya was inspired to use unorthodox materials, so he researched alternative design methods and contacted architect Nripal Adhikary from ABARI, or the Adobe and Bamboo Research Institute.
“I told my neighbours that I’m making my house from the earth, and they were so confused,” Acharya remembers. “Nobody did it.”
Acharya corralled workers from Jumla, his hometown, to train Nepalis uninitiated in the architectural craft. He spent more than a year procuring the materials, testing the soil, training the labourers, and at last, building the home. But the biggest challenge was simply explaining what he was doing.
Although he’s part of a burgeoning movement promoting the environment, the wider Nepali society is still largely unaware of these forms of sustainable architecture. But now Acharya is joined by firms like ABARI, Sustainable Mountain Architecture and others in the world of environmentally-friendly design.
“I taught people to believe that you can build a durable home out of soil,” Acharya says. Rammed earth walls are created by ‘ramming’ together layers of soil, sand, stone, dust, and occasionally cement. Acharya built an earthquake-proof, eco-friendly home using monolithic load-bearing walls. He rammed them into Italian-imported, recyclable plastic forms bolted to wooden planks, locked together in straight, upright positions to prevent bulging. To ram the walls, he ground the soil into a fine powder, filling the forms with 10 centimetres of earth mixtures rammed down to two inches. Acharya was careful, as too much clay would crack and shrink walls. He reinforced the structure with concrete beams and a flexible, lightweight second storey roof truss structure of bamboos to promote better earthquake-resistance. The house is unique for using wooden floors recycled from demolished buildings in Kathmandu, and bathroom windows from wine bottle glasses.
Bamboo may seem a strange accompaniment to rammed earth, but its beauty lies in its durable, but lightweight characteristics. It ends up lasting longer than conventional materials once treated. During the bamboo-treatment process, starch is extracted from each bamboo stick and replaced with preservatives.
“Imagine a brick and wood house,” Adhikary says. “Everything that is wood is bamboo, and everything that is brick is rammed earth.”
The benefit of using rammed earth is that it’s often faster to work with and has no transport costs. “It’s something that you can use right under your feet,” says Adhikary. “It’s also material that doesn’t go through any chemical changes like concrete.”
Since soil quality is the biggest concern for builders, rammed earth walls require proportionate clay and sand, and the complete absence of topsoil. The local soil is tested in a water-filled jar, revealing the soil layering and correct mixture of clay and sand.
There are many advantages to rammed earth walls. When formed properly, the resulting walls resemble sedimentary rock, often at a thickness of 16 inches, which offers better thermal properties than brick or cement homes. Traditionally, the walls were 30 inches, but now they are as small as 14 inches, allowing constructors to build quickly. The thermal qualities reduce the need for air-conditioners, fans, or heaters, thanks to improved ‘lag time’ afforded by the thermal properties. Acharaya’s home can absorb, store, and release heat over a lag time of 10-14 hours.
“I used to live in a concrete home,” Acharya says. “I had one heater in each room. Now, during the summertime, I don’t even need to open the windows.”
The history of rammed earth in Nepal can be traced back to upper Mustang, where small, plastered blocks of rammed earth were used to build homes. Contemporary rammed earth has changed drastically from those humble beginnings. Nowadays, big formworks are used instead of small blocks, and no plastering or painting is done at all.
Earthquake resistance has also changed the process. Concrete reinforcement is now de rigueur, and lightweight materials like bamboo are favoured for promoting earthquake resistance. Acharya’s home is built like a hyperstructure—if the rammed earth structure fails, the bamboo remains standing because it is made out of a different material. His ground-floor design is also built according to three symmetrical rectangles with unconnected foundations, so during earthquake tremors, each unit will shift independently and prevent any damage.
But it’s unclear if rammed earth is for everyone. Adhikary notes that it’s mostly middle-class urban environmentalists who experiment with rammed earth. In Nepal, concrete is still considered modern, and earth materials continue facing a stigma that they are unsophisticated, outdated, and lower-quality.
This makes appealing to Nepal’s rural dwellers challenging, as Adhikary mentions. “Even though it’s a cheaper material and perfect for the rural environment, people don’t want to use earth materials because there’s a stigma.” Many Nepalis who grew up in mud houses think it’s old-fashioned and prefer concrete when expending money on a new home.
“For people who’ve always lived in an earthen house, they think it’s labour-intensive to maintain it, and it doesn’t carry the status of concrete,” Adhikary says.
Acharya experienced this firsthand. “When I started, my family thought I was mad,” Acharya recalls. “They kept saying why, why, why?” Acharaya’s mom even asked him, “Son, you’re going to build a mud house? You’re using your own money: is it durable or not?”
Still, the cost is one reason to reconsider rammed earth and bamboo. The materials are commercially cheaper, and the home demands virtually no heating or cooling costs. For a more sustainability-minded generation, it may be enough knowing that energy bills and costs to the earth will be lower. Not to mention that the unique design may survive beyond one’s lifetime.
Published: 21-06-2014 08:55