Designing climate-resilient shelters: lime-stabilised soil shelters for Rohingya refugees

The Rohingya refugee crisis in Cox’s Bazar, Bangladesh, has posed significant challenges for the shelter sector. Since 2017, the area around Cox’s Bazar has hosted almost a million Rohingya refugees in what was previously a wildlife sanctuary. Given the number of refugees, space is extremely limited. Additionally, as the camp is situated within a protected forest, the government has imposed restrictions on the materials used to construct shelters. Only temporary shelter materials that have minimal environmental impact are permitted by the authorities.

Bangladesh is one of the world’s most vulnerable countries to climate change, experiencing increased frequency and intensity of floods, cyclones and heatwaves. The refugees in Cox’s Bazar are particularly vulnerable. Since 2017, these communities have faced several tragic incidents resulting in extensive damage to their shelters and belongings and the loss of many lives. This vulnerability is amplified by the current shelter materials, which are unable to withstand extreme weather conditions such as cyclones, floods and landslides, and are also not fire-resistant.

To address these challenges, shelter partners and the Shelter–Camp Coordination and Camp Management Sector are working jointly to find innovative solutions that promote the sustainable use of resources in shelter construction and work within the government’s restrictions. The International Organization for Migration (IOM) has initiated a pilot project that focuses on enhancing resilient shelter solutions using lime-stabilised soil (LSS) construction. The project aimed to address these challenges by providing shelters that withstand extreme weather conditions and fire hazards, offering a sustainable solution for displaced populations.

The solution – lime-stabilised soil shelters

This pilot project leverages existing materials in combination with lime, soil, rice straw, rice husk ash, and brick dust. These materials are readily available in the local market. IOM has undertaken a series of extensive experiments and studies with the aim of discovering the most effective combinations of materials suitable for application to the various components of a shelter constructed from bamboo, which can be applied to the roof, wall and floor. These efforts aim to determine the optimal solutions for enhancing the robustness and strength of such structures, while improving their overall safety and comfort levels. These local materials not only offer technical advantages but also bring enormous economic benefits and create a pleasant living environment for the users, making it a practical and effective solution.

Limestone, a naturally occurring sedimentary rock rich in calcium carbonate, plays a foundational role in creating materials for LSS shelters. When limestone is heated, it undergoes calcination, which removes carbon dioxide, resulting in quicklime. Quicklime, an essential ingredient in lime stabilisation, is highly reactive when mixed with water, producing slaked lime. This slaked lime acts as a binder that can be combined with soil to enhance its durability, moisture resistance and cohesion, which are essential qualities for LSS shelter construction. A lime-based plaster provides a fire-resistant, breathable and crack-resistant finish, protecting the shelter from external weather conditions and reducing the risk of mould and dampness inside. This application of quicklime in LSS construction thus contributes to creating more resilient and sustainable shelter solutions for refugee camps.

The lime-stabilised soil and its application in the bamboo shelter proposed here have, among other things, two significant advantages: the ingredients (clay, sand and lime) are locally available at a reasonable cost in most areas, and the implementation requires neither modern equipment nor the use of fuel for plastering the wall, structural bamboo, roof or floor; a simple manual press is sufficient. In this pilot project, lime-stabilised soil plaster is used to protect the bamboo structure, including walls and roof, from fire, and to provide stability underwater during periods of flooding.

In refugee camps, lime-stabilised shelters provide significantly enhanced protection from weather- related hazards. In particular, they provide:

• Comfort from extreme heat: People living in Rohingya camps endure intense summer heat, which is increasing because of climate change, primarily due to the nonexistence of roof insulation. LSS shelters offer good thermal insulation properties, helping to maintain comfortable indoor temperatures. The lime-stabilisation process creates air voids within the soil, which function as natural insulators, and a drop of 5–7ºC compared to the outside temperature is observed during summer.
• Flood resilience: Bangladesh, situated in a funnel-shaped bay, faces the brunt of cyclonic storms each year. Its susceptibility to disasters is a pressing concern. In response, LSS shelters have been ingeniously designed to withstand a range of calamities, including monsoons and flooding. The lime- stabilisation process fortifies the soil, granting these shelters remarkable strength and stability. This resilience is pivotal in safeguarding communities vulnerable to frequent natural hazards.
• Fire resilience: The commonly practised shelter modality consists of bamboo, ropes and tarpaulins that are at risk of fire. LSS-plastered bamboo shelters form a protective barrier that can help prevent the rapid spread of fires between densely populated shelters and reduce casualties.
• Energy efficiency: LSS has thermal insulation characteristics that help reduce the need for artificial heating and cooling, leading to lower energy consumption. This is particularly valuable in humanitarian settings where access to energy resources may be limited or unpredictable.
• Low-cost maintenance: LSS shelters require minimal maintenance over time. The lime-stabilisation process improves the durability of the soil, reducing the need for frequent repairs. This is beneficial in resource-constrained humanitarian settings where ongoing maintenance can be challenging.
• Enough adaptability to allow local and cultural architectural identity: The construction technique of LSS shelters allows for the integration of traditional architectural elements and design features, ensuring that the shelters reflect the cultural identity of the Rohingya community. This promotes a sense of cultural continuity and pride among the residents.
• Environmental benefits: Lime is an environmentally friendly construction material with a lower carbon footprint. LSS shelters support climate change adaptation and preserve natural resources by utilising locally available soil and minimising non-renewable resources.
• Sustainability: Using locally sourced materials, LSS shelters minimise environmental impact and promote sustainability. Using lime reduces construction’s carbon footprint, as lime production emits limited greenhouse gases compared to traditional cement production. It requires minimal processing of materials, reducing the environmental impact of construction and transportation. Additionally, LSS shelters can be designed to incorporate eco-friendly features like natural ventilation and rainwater harvesting.
• Scalability and replicability: The technology and construction techniques are relatively simple, allowing for easy transferability to other humanitarian settings. This scalability makes LSS shelters viable for addressing the rapidly growing global demand for affordable and climate-resilient shelters. The time it takes for people to learn how to apply lime-stabilised soil to bamboo shelters depends on factors such as prior experience, construction knowledge, familiarity with bamboo, lime and soil as building materials, and the individual’s learning ability. Practical training for a full day can improve the skills of the workers, but it may take a few days to a week for individuals to become proficient in applying lime-stabilised soil on bamboo shelters. Practising and gaining hands-on experience are essential for mastering these techniques.
• Local economic development: The construction process creates employment opportunities and stimulates the local economy. Additionally, using locally sourced materials reduces the reliance on imported construction materials, saving costs and supporting local businesses.
• Community involvement: Implementing LSS shelter projects often involves community participation, empowering residents to contribute to the construction process. This approach promotes community engagement, ownership and skill development. It also creates knowledge transfer and capacity- building opportunities, enabling communities to take charge of their own shelter.

Lessons learned

After introducing the LSS shelter technique to the community, it became evident that certain key points from the introduction held significant importance. The four crucial aspects were:

1. Community engagement. It is crucial to promote community engagement for the successful implementation of the LSS shelter technique. We have found that involving the community from the early stages of the project fosters a sense of ownership and empowers individuals to actively participate. Hosting community consultation meetings, workshops and training sessions helped to build trust, gather feedback, and address any concerns or misconceptions.
2. Leveraging local knowledge and expertise. Recognising and leveraging local knowledge and expertise is essential. Engaging with local engineers, architects, craftsmen and labourers allowed us to tap into their experience and skills. This collaboration not only enriched the project but also ensured the sustainability and long-term success of the LSS shelter technique.
3. Training and capacity-building. Providing comprehensive training and capacity-building opportunities is vital. We learned that offering hands-on training sessions, practical demonstrations and continuous support helped individuals grasp the technical aspects of implementing LSS shelters. Regular follow-up sessions and mentoring played a significant role in reinforcing the learning process.
4. Communication and information dissemination. Effective communication is key to creating awareness and promoting adoption. We found that using various communication channels, such as community radio, posters and local language materials, helped disseminate information about LSS shelters. Engaging local influencers and community leaders as advocates also proved to be effective in spreading the word and generating interest.

These elements proved essential in ensuring the success and sustainability of the project. Looking ahead, while maintaining a strong focus on community engagement, local expertise, comprehensive training and diverse communication channels will remain unchanged, it would be beneficial to conduct a thorough baseline assessment to better understand the specific needs and challenges of the community; establish partnerships with local organisations and institutions to enhance project sustainability and expand reach; and implement a monitoring and evaluation framework to track progress and gather data for future improvements.

In the face of climate change, innovative solutions emerge from the most unexpected places. The LSS shelter project demonstrates that practical action can combat the challenges posed by our changing world. These pilot shelters, nestled within refugee camps, have proven their mettle. Their fire resistance, disaster resilience and durability make communities less vulnerable. Lime, an ancient construction material, weaves itself into the fabric of Bangladesh’s vernacular architecture. Centuries of wisdom now find a new purpose. Locally sourced materials minimise transportation, nurturing the very communities they shelter. Lime is crucial for reducing the project’s carbon emissions, substantially lowering its overall carbon footprint. Additionally, it enhances the durability of the structures, providing robust protection against environmental degradation and weather-related challenges. As these structures rise, they harmonise with nature – a testament to eco-friendly coexistence and an inspiration to those everywhere hoping to replicate them.

Dabal Kaji Rokaha is Programme Manager, Shelter/NFI.

Mohammad Ali Mamun is Shelter Technical Expert, International Organization for Migration.