Strong earth

15 min read
24 Mar 2017
15 min read
1865 words
A handful of architects have come up with ways to build structurally sound, aesthetically pleasing mud-house models that Nepalis would readily adopt if only they could get past their qualms

Atop a hill in Dhulikhel sits a three-storey rammed earth house. The house has sloped roofs and brown mud walls. The inside of it is furnished with wooden furniture to align its aesthetic to the natural feel of the house, and even as the sun blazes outside, it’s pleasantly cool inside the house. This house was built by Nripal Adhikari, CEO of Abari, before the earthquake, and while plenty of other mud houses in the area succumbed to the earth’s tremors, Adhikari’s house remained standing. Till today, the walls of his house do not have a single visible crack or structural damage. According to Adhikari, the key to building strong mud homes such as his is to incorporate modern techniques into traditional building practices. As proof for that claim, he merely has to refer to his house.

After the April 2015 earthquake, countless houses built out of mud—across Nepal—got destroyed or severely damaged. Unsurprisingly, mud houses were criticized for their structural fragility. But Adhikari’s organisation—Abari—and a few others like his have demonstrated that mud houses can be made earthquake-resistant and structurally sound as well. If these architects can sell their idea to Nepalis, the earthen-house models they have developed could become more prominent in both urban and rural environments.

After the April 2015 earthquake, countless houses built out of mud—across Nepal—got destroyed or severely damaged

Each organisation employs a different approach for making their mud houses earthquake-resistant. Abari, for instance, uses thick concrete belts to evenly distribute load across a mud wall, and the construction company Matoghar uses traditional wooden beams to similar effect. 

Adhikari’s home in Dhulikhel has a concrete belt that spans the perimeter of the mud walls, right below where the roof meets the walls. This belt not only distributes weight over the length of the wall, it also helps to hold the mud wall together. Adhikari also uses earthen bricks held together by mud mortar, but his home was made using rammed earth techniques. When using rammed earth to construct a house, the engineers create a thick mud-base with sand, concrete and rock dust mixed in to give it strength, and they tamp down each layer of mud as they build the wall. Usually, during the construction of rammed earth houses, engineers tamp a 3.9-inch mud wall down to two inches to give it the ideal structural consistency.

Build up Nepal is a not-for-profit company that focuses on building rural houses with earth bricks that are exceedingly robust. Björn Söderberg, the managing director of the organisation, believes in constructing the strongest buildings possible—regardless of what materials his company uses. Build up Nepal constructs buildings made out of unbaked bricks and mud-compound mortar. The company also insert into their bricks a host of other materials like concrete and fine sand to give them structural integrity. Their bricks have two holes in the middle and through these is inserted reinforced steel rebar. All these reinforcements help hold the entire brick structure in place during a tremor. Like Adhikari, Söderberg also uses concrete belts to hold mud walls in place, but he also uses multiple belts at even intervals to further strengthen the house.

Hemendra Bohra, the founder of Matoghar, uses rammed earth too, but he uses a slightly different technique from Adhikari. In his model, the foundation of the building is first laid by construction workers’ digging approximately three feet deep, and filling the depression with monolithic stones. A layer of concrete is then laid atop these stones and steel rods protrude upwards and out of the concrete. Earth—preferably sandy soil with 10 to 20 per cent clay—is then tamped around these rods so that all the walls (made from the rammed earth) will have both vertical and horizontal rods passing through their entire length. To further reinforce the structure and to hold the walls in place, a wooden or concrete beam is used as tie beams.

“There are some limitations to this building technique,” says Bohra. “Walls of rammed earth houses can only stand so much rain before they start to erode. But this can easily be overcome with some measures, such as raising the level of the house and constructing overhanging roofs. The buildings need ‘good boots and good hats’ for the monsoon. The walls also need to be coated with material such as linseed oil to make them as impermeable as possible.”

Overhanging roofs—with eaves several feet longer than in most sloped roofs—area necessity for earthen houses since mud is erodible. Because Nepal experiences heavy rainfall during the monsoon, wet mud walls can lose their layers. Adhikari also uses overhanging roofs to protect the walls from water damage. For Söderberg, water damage is not much of an issue since he uses a lot of concrete to hold the mud in place. But for raw mud structures, a coating of natural glue, as used by Adhikari, could help keep the dampness out of the walls.

But having an overhanging roof means you need a larger compound for your house. And the fact that the walls of these houses need to be considerably thicker for the sake of structural integrity also means you need a larger construction space. All of this translates into higher costs for people planning on building mud houses in urban areas, where the land prices are unaffordably high. But that’s not the case in the rural areas. The primary reason why mud houses will be cheaper in rural areas is also because the raw materials are easily available there. Building an earthen house in urban settings would mean having to transport large quantities of mud from outlying village areas. While concrete, mortar and rebar are cheaper in cities, their use in mud houses are limited, and thus mud houses built in cities would not cost significantly lower than their concrete counterparts. But in the long term, the savings on heating and cooling would contribute to bringing down overall costs: since mud acts as a natural insulator and retains thermal mass. Owing to these properties, mud houses are cooler during the summer and warmer during winter than concrete buildings.

But will people actually want to live in mud houses? Mud houses in general are still perceived as cheap, weak buildings that only low-income families settle for. Concrete signifies social prominence, and thus people tend to want to invest in a building made out of concrete. “Also since people with prominent social standings still tend to gravitate towards concrete housing, many low-income people as well as middle-class people tend to want to do the same if they have the means,” says Bohra. “My hope is that richer folk in rural areas—after having understood the advantages of mud buildings—begin to adopt designs made by companies such as ours. If that were to happen, we can remove the stigma associated with mud, and perhaps the lower-income folk too will want to build with mud. Thing is, it is only after people have started implementing earthen housing that people truly understand how structurally sound and aesthetically pleasing these buildings are. And in urban areas, people who want to live in buildings that are not informed by the same cookie-cutter aesthetics employed in concrete houses could opt for modern mud houses too.”

The stigma around mud houses became worse after the 2015 earthquakes since many mud houses—built without proper reinforcements and construction techniques—got reduced to rubble. But as the earthen housing experts claim, such damage was mostly a result of shoddy building techniques and engineers’ not adhering to design standards. Many older mud houses that fell didn’t have reinforced belts and load-bearing pillars. Moreover, even the composition of the mud wasn’t as refined as is used in modern mud architecture. To counter the negative notions surrounding mud houses, many proponents of mud houses have built their own houses with unbaked bricks and rammed earth techniques. They hope that their houses will serve to prove the idea that mud houses make for good-looking, earthquake-resistant and cheaper alternatives to concrete buildings.

They believe that for people in urban settings the ‘heritage aesthetics’ of the building as well as the higher thermal mass properties of the houses could be a draw. And proprietors of businesses such as resorts, cafes and hotels could benefit from investing in earthen houses because these buildings would stand out in a sea of concrete buildings. As for people in rural areas, say the architects, they need to think functionality and cost first—over their house’s being primarily a status signifier.

But at least some NGOs and INGOs working with reconstruction efforts in Nepal have understood that mud architecture is the way to go, say the architects. The low cost of building modern mud houses in rural areas has allowed these organisations to build more houses within their budget. For these organisations, mud architecture is also made all the more attractive because if they make use of mud, they will not have used bricks that were produced in brick kilns-which are notorious for polluting the air. “Mud houses might not be as feasible for most urban residents. But if we can win rural people over, they could someday become the preferred choice among the rural populace,” says Adhikari. “I actually hope to see Nepalis adopting modern mud houses at such a scale that our cities and villages become known for their unique mud-architecture style.”