Foundations for sustainable buildings in Nepal
It was 2AM on 11 June when a 4.7 magnitude earthquake shook Kathmandu residents from their sleep, but it is doubtful if it will jolt many out of the complacency about seismic risk.
The tremor did not cause any damage, but it brought back memories of the 2015 earthquake, and forced some to reflect on the safety of Kathmandu’s buildings. The 2015 quake that saw the collapse of predominantly brick, mud, and mortar buildings, feeding public perception that concrete structures are more durable.
However civil engineers and architects say technologies like rammed earth would be environmentally more sustainable and earthquake-resilient. But reinforced concrete is preferred, with Nepal’s domestic cement production more than tripling from 3 million tonnes to 10 million tonnes in the six years since the earthquake.
By coincidence on the day of the 11 June quake, rammed earth architects gathered for a workshop in Patan to take stock of progress so far.
Rammed earth construction uses locally-sourced soil often combined with gravel and reinforced with steel bars and limited concrete. It involves no machinery and therefore less emission, a contrast to brick kilns that contribute heavily to Kathmandu’s pollution. Materials are also largely sourced locally, which reduces both cost of transportation and fossil fuels.
Narayan Acharya, the director of Sustainable Future Nepal, built his own house in Kathmandu with locally-sourced materials and rammed earth techniques. He has now built 10 more structures in Kathmandu Valley.
“It is warm in the winter and cool for the monsoon, we should promote that all over Nepal,” says Acharya, adding that rammed earth structures are both sustainable, comfortable and retain the traditional Newa style. While the walls are made of soil and other material, the structures are resistant to monsoon weather. He also has a built-in water recycling system and a biogas tank.
Rammed earth projects have been particularly successful in Nepal’s rural environments. In 2020, the Bayalpata Hospital in Accham was built with rammed earth technology and won international design awards. Despite these successes, rammed earth structures have yet to establish a hold in Kathmandu.
“There are not as many rammed earth structures in Kathmandu proper,” explains Tyler Survant, an architect and founder of Better Building Bureau, alongside Anna Leshnick.
One reason for the lack of rammed earth structures in Kathmandu is the misconception that mud mortar buildings are weaker. In 2015, the majority of fallen buildings in the earthquake were brick and mud mortar. But those fallen buildings were not built with rammed earth techniques, and many violated building codes.
“They do not believe mud is strong enough,” says Acharya about rammed earth structures. “It is important to overcome that misconception.”
Experts warn that public confidence in concrete construction is misleading. “Do not believe for a second that concrete won’t be impacted in an earthquake,” says Jharna Joshi, an architect and professor at Kathmandu University. Even a slightly longer or more intense earthquake could have also brought down concrete structures in 2015.
According to Survant, current building codes limit rammed earth structures to two and a half stories, making them less popular in a dense, city environment that builds upwards even though rammed earth buildings can go up to three stories.
Read also: Quake was a learning experience for Nepal’s schools, Prakriti Kandel
Building codes require adjacent residential buildings, even in concrete, to not exceed three stories, but contractors often add additional floors on top of existing structures. “There is a building code, but people do not follow the rules. And since land is very expensive, some build six stories to not lose any value.”
Acharya says his rammed earth structures did not crack in the last earthquake. Earth buildings are used internationally and historically, with structures found in Chile, India, Nepal, and Iran. “Earth structures have been part of vernacular for millenia, and they have tested it,” says Survant, explaining that rammed earth structures use reinforced ring beams, steel bars, and up to 10% concrete that interlock the earth walls.
“The concrete and rebar is providing the same support, but with far far less concrete and using local materials,” he adds.
Rammed earth’s costs come from its added insulation, and the experienced builders required, including a structural engineer. It also reduces other financial and environmental costs. There is far less transport of concrete to a building site, and no brick production in polluting kilns.
“If you calculate all the costs, it is competitive, this can be cheaper,” says Acharya. “And rammed earth is not just for the short term, it is built to last.”
Rammed earth’s materials are unlikely to contribute to future waste and environmental impact because when demolished, the material can be reused.
Joshi explains that after the 1934 earthquake, Kathmandu was rebuilt with traditional timber salvaged from previous structures. After 2015, most buildings are now concrete. “We need to upcycle existing materials. If you build in concrete, there is no way you can reuse those materials,” she adds.
Read more: Nepal’s traditional seismic resistant designs, Sheilin Teo