THE POTENTIAL OF MUD: THE ORIGINAL BUILDING MATERIAL
Mud is considered to be the poster-child in terms of what we consider to be a “natural building material”. Yet, it tends to be underutilised and passed over in favour of more high-tech, energy-intensive materials, even in contexts where it is ubiquitous, and where there is a need for low-cost building materials. For a recent team-building exercise at SKDO, we got our hands dirty (quite literally!) and experimented with different types of sample mud plaster mixes and proportions. This got us thinking more about the potential of mud in the context of affordable housing…
Fig. 1: A mud plaster sample using straw as the binding material dries in the sun and reveals the straw that holds it all together
What are some ways to build low-cost structures for affordable housing in India?
The affordable housing target: The Ministry for Housing and Urban Affairs (MoHUA) of the Government of India has announced that it will catalyse the construction of 20 million new homes by 2022 under the Housing for All scheme of the Pradhan Mantri Awas Yojana (PMAY).
The focus on prefab and precast technologies: According to government policymakers, one of the means by which this can be achieved is by utilising precast and prefabricated technologies at a mass scale.
The challenge with achieving economies of scale: However, the economies of scale required to make prefabricated technologies more cost-effective than cast-in-situ brick and concrete construction is still some way away in India even in the midst of a construction boom, and requires an administrative and operational overhaul in the way real estate (and unorganised, unskilled labour) functions in India.
Structural economic challenges: To make matters worse, the real estate sector is going through a slump at this point in time due to a host of structural factors, pushing affordable housing targets even further out of reach.
The need for local alternatives: using locally available materials, skills and labour, therefore, might be the need of the hour when trying to meet affordable housing targets in the Indian context. This, therefore, brings us to mud construction.
What is the potential for mud construction in rural areas?
It is one of the most ancient, tried-and-tested ways to build: Mud is quite possibly the most ancient building material known to man. Clay bricks were found at archaeological sites of several ancient civilisations, most notably Mesopotamia, the Harappan civilization, and ancient Egypt. There are magnificent, ancient multistorey mud structures still standing in parts of the Middle East and Sub-saharan Africa, most notably in the Yoruba architecture of Nigeria.
It is ubiquitous in rural India: It is also the standard building material in rural India today, and has been for unbroken millenia in several forms. Today, however, it is fast becoming replaced by reinforced cement concrete, cement plaster, and even flyash brick, all of which are produced using electricity and industrial processes and for which raw materials need to be transported across distances, especially when building in remote rural areas.
What are the different types of mud construction? Are the raw materials really ubiquitous?
Rammed earth walls – this is roughly equivalent to a cast in place concrete wall, and there are ways to layer different colours of mud to achieve a spectacular result. It also uses less electricity and power than concrete construction, while achieving a similar effect. This does require some skill and know-how, but the spectacular result is worth it. May not be appropriate for the average low-cost dwelling, however.
Cob – a mixture of mud and a binding material (straw, agricultural waste), with high thermal mass. In India, we definitely have a lot of agricultural waste and we need to figure ways to use it. This is as good a way as any.
Wattle and daub construction – Walls built on a bamboo frame and then plastered with mud. We are also one of the largest producers of bamboo in the world, and literally every city has a bamboo market; for small and medium construction projects, bamboo scaffolding still tends to be common.
Sundried (adobe) or compressed earth brick – Mud is compressed by mechanical means; and therefore more sustainable as it is less energy intensive than fired brick.
Mud plaster – Used in wattle and daub construction as well as over any type of brick – there are several different mixes and proportions, but almost always, the basic element involves a base material (mud), and a binding material (straw, rice husk, lime, cowdung, and a host of other waste materials common in rural areas) that ensures that the mud plaster does not crack.
Fig. 2: Applying mud plaster on a wall is labour intensive but requires no particular skill
Okay, makes sense, but what are some of the use cases in which mud makes more sense than other, more conventional building materials?
The advantages are numerous: mud walls are thick, thermally insulating, soundproof, aesthetically pleasing (it is quite literally the posterchild for a “natural-looking” material), materials are easily available locally, particularly in a rural context, and it can be recycled at a lower cost. Some things to consider when deciding whether mud construction is the right choice for a project:
The potential for design: Designwise, it’s versatile – curves are no problem, in fact mud is tailormade for creating complex organic shapes in plan, section and elevation. In that sense, it’s similar to the childhood toy “plasticine” — as long as you can shape it with your hands, you can make it in mud.
It’s sustainable! …It is less energy intensive than concrete and fired clay brick, and easily recycled. But it does deplete valuable agricultural topsoil, and so should not be used in contexts where the topsoil has to be removed and brought in from elsewhere i.e. most small urban plots. It makes sense to use mud when sourcing it from the same plot in which the the house is located. The depression caused by the “mud quarry” can then become a pond or reservoir, adding to the architectural quality and water security of the dwelling.
But it tends to be very slow. Most mud construction processes rely on human muscle power. This tends to mean that the economic case for mud is best suited to use cases where mechanisation and industrialisation is cost prohibitive i.e. remote rural locations. However, when compared to hand-mixed and poured concrete (the norm for small to medium projects especially in rural locations), it compares rather well in terms of time.
It tends to be easily repaired – materials are easily available, and it requires a pair of hands and no particular special skills. But because it is so labour intensive, and, quite literally, handmade, it only makes sense to consider in contexts where labour costs are not prohibitive. Constant maintenance and touch ups to ensure moisture and termite resistance, too, mean that it is best suited to labour-rich contexts.
The tactility of mud: The labour intensive processes utilized in mud architecture, too, from a cultural and emotional standpoint, lend a tactility and organic character to mud buildings that modern (largely) rectilinear framed structures tend to lack. One can quite literally see a mud building shaped by human hands. At our recent mud plaster workshop team-building exercise, we were struck, for example, by how the process of creating mud plaster engaged all of our senses and brought us psychologically closer to the process of creating buildings out of natural materials. It was no longer an intellectual exercise: instead it became sensual, tactile, and instinctual. We felt, however briefly, as though we had the power to shape our spaces with our own hands. For example, one team member recalled the experience of playing in mud puddles and messing about in the garden as a child, and how this took her back to that experience.
The psychology of “kacha” and “pukka”: Unfortunately, when it comes to market feasibility, even in remote rural locations where mud is a perfect fit, there is an aspiration for a brick and concrete house as a result of longstanding government policies in India that classify mud houses as “kacha” and fired brick, cement plaster and concrete houses as “pukka” for the purposes of determining habitability. Therefore, despite its potential, mud architecture tends to remains the domain of the rural poor who tend to want to graduate out of mud houses, or an esoteric departure from the mainstream in the case of wealthy clients who specifically ask for mud houses as an aesthetic element.
Pros and cons aside, however, mud is a ubiquitous, less energy intensive alternative to customary building materials, and its full design potential remains largely untapped and worth exploring by designers, architects and policymakers.
