How Marla Kohli’s Bamboo Research Supports the Hilti Foundation's Mission
Marla Kohli has always been fascinated by bamboo. Growing up in Peru, she loved exploring Lima’s historic center, the centuries-old Ciudad de los Reyes (City of Kings), where the upper walls of many of its loveliest buildings were constructed using the material.
It was not just their beauty that resonated. For the uninitiated, bamboo might seem a flimsy construction material. Yet Lima’s buildings have stood for hundreds of years. Moreover, the Spanish colonists who built Lima deliberately chose it as a solution to the frequent earthquakes that imperiled the city, using a construction technique similar to the indigenous quincha method used for centuries in the Andes.
It was not, of course, a colonial invention. Long before Columbus made landfall, indigenous South Americans had used bamboo lattices coated with earth in a wattle-and-daub technique known as vernacular bahareque. Not only was this style of building economic, practical and durable, it made even larger structures strong enough to withstand the forces of nature—something that made an impression on Marla’s young mind.
After spending 14 years in Peru, Marla, at age 18, went home to Switzerland and enrolled in a civil engineering course at ETH Zurich, a university famous for its science and engineering programs. Even as a young child she had been fascinated by buildings. “I remember as a child, when I was probably about four or five, my grandparents had these magazines where you could order flowers,” she recalls. “On the last page, there was a design for a family house with a floor plan and I would collect every one of them, even then.”
Life was tough in Zurich initially: “My thoughts were formed in Spanish and I still counted in Spanish,” she says. “At the age of 18, I had to rebuild my life in what felt like a different culture. It was a shock to the system.” Still, she prevailed. When it came to doing her master’s degree, her mind wandered back to Peru and its ancient bamboo building traditions. As she pondered her thesis topic, she wondered how she could marry this with a developing interest in environmental sustainability. “My first impulse was the connection I had with Peru and its vernacular system,” she says. “I’m generally fascinated by these vernacular systems because I think they have this ancient knowledge that may hide regenerative solutions for the construction sector.”
And so was born an idea that would take Marla thousands of miles away to the Philippines and a collaboration with BASE Bahay, a Hilti Foundation initiative with bamboo at its core. Like Peru, the Philippines is prone to natural disasters, suffering from both typhoons and earthquakes. Starting in 2012, Hilti developed what it calls Cement Bamboo Frame Technology (CBFT), a bahareque-inspired technique combining indigenous South American building traditions with European engineering know-how, adjusted for the traditions and environmental conditions of the Philippines.
For the next decade, based on the pioneering work of Corinna Salzer, a Hilti employee whose doctorate formed the basis of CBFT, the Hilti Foundation investigated and promoted bamboo construction technologies that could answer Southeast Asia’s affordable housing needs, setting up BASE Bahay as its implementation vehicle. The aim was to introduce an affordable, sustainable and disaster-proof building technology and housing solution for low-income families, not just in the Philippines, but potentially throughout the tropical bamboo belt that stretches across much of the global south. The people living in this area account for most of the 1.8 billion people that, UN-Habitat estimates, live in inadequate housing.
“The beauty of using bamboo in these countries is that it’s locally grown,” says Matthias Gillner, chairman of the Hilti Foundation. “So, you are able to develop a full supply chain using primarily local material without having to import timber or steel. You create local jobs for farming and treating the bamboo as well as pre-assembling the CBFT elements. By using bamboo, you are also capturing CO2. You therefore have two pluses, the economic and the ecological.” The program has already had a significant impact, with BASE and its partners building over 2,300 homes sheltering 10,500 individuals across the Philippines, Nepal, India, Sri Lanka and Nicaragua.
But the foundation was also keen on exploring opportunities for further research into sustainable and affordable construction, with a particular focus on bamboo. And so, in 2021 it founded the BASE Innovation Center in Manila to explore how bamboo, one of humanity’s oldest building materials, could be incorporated into modern construction. It was, says Luis Felipe Lopez, general manager at BASE Bahay, high time that proper research was conducted into bamboo.
“Bamboo was never taken seriously by engineers for a single reason,” he says. “There is no bamboo in Europe and there is no bamboo in North America, in other words in the areas where modern engineering was created.”
The innovation center has taken a big step towards correcting that anomaly by collaborating with universities across the world, including ETH Zurich, where Marla was doing her masters. ETH was one of a handful of Western universities that took bamboo research seriously, but the university also suffered from a serious limitation: it had to import all the bamboo it needed, restricting the number of studies that could be conducted. BASE’s innovation center provided an answer to the problem. “It was decided it would be better and cheaper to send students to the Philippines where they can test bamboo as much as they want, rather than ship bamboo to Zurich, where it is like gold dust,” says Carlo Cacanando, a research and development engineer at BASE.
So, Marla flew, with a mixture of excitement and trepidation, to the Philippines, to join an initiative matching the strengths of the global north and south for the benefit of the global poor. With Luis, Carlo and others on hand to provide a wealth of knowledge and experience, not to mention an unlimited access to bamboo, Marla began work on a thesis she would entitle “what insights can cement bamboo frames glean from vernacular bahareque?”—a thesis that would eventually be recognized with a top prize from ETH.
As with other students joining the program, the purpose of Marla’s work was to help address knowledge gaps in bamboo construction. ETH has already done important work on evaluating the environmental impact, including the carbon footprint, of the CBFT technique. Marla focused not only on this aspect but also carried out tests on different configurations of shear walls containing a bamboo frame to examine their resistance to earthquakes and typhoons.
In a significant breakthrough, she found that covering the frame matrix with an earth plaster was a viable alternative to cement. Not only did tests show that it could withstand the lateral forces unleashed by a natural disaster like a typhoon, it was also more environmentally friendly than cement. While further tests are needed to produce conclusive results, and additional research is required on appropriate backing for the walls, it is a significant step forward, notes Luis Felipe Lopez. “I think the most important part of Marla’s thesis is that she was able to prove that using mud is as good as using cement,” he said. “It’s changed the perception that cement is the only solution. There are still other issues to solve, but environmentally speaking, it is super good.”
For Marla, the experience of working on her thesis in the Philippines has been transformative, she says. Not only did she have some of the world’s leading bamboo experts a door knock away, but she also got to see firsthand the importance of her work when she visited a village BASE had helped to build—something that would never have happened had she stayed in Zurich.
“It was the direct, hands-on collaboration and exchange that truly made the difference,” she says. “Implementing the earth plaster and facing the local challenges, such as not having ready-made earth plaster mixes, was a collective effort. From sourcing the earth sample to preparing the bamboo fibers and mix, to finally applying the plaster to the frame’s matrix, we all got our hands dirty. It was a shared success, and the entire lab team celebrated the achievement together.”
“One of the most fulfilling moments of my thesis was when Ayen, one of the workers at the lab who helped build the panels, asked me for the recipe for the earth plaster. He wanted to try it at home. Despite the language barrier, I realized that I had convinced at least one person—and that meant the world to me.”