Mud fantasy

Pappal Suneja

Mud is a cost-effective material that has  been used for construction since ages. However, with the focus shifting to eco-friendly and sustainable homes oflate, mud has once again emerged as a building material, though in a new avtaar, in the 21st century. It is being seen as an answer to housing scarcity, especially in rural and remote areas. Mud construction is mainly suitable for places that are relatively dry and have abundant mud available. Mud is a very versatile building material as it can be molded into any form, as a building block it can be used as cob, adobe, wattle & daub, compressed stabilised rammed earth etc. The application of the same can take place in flooring, walls, partitions, interior embellishments, fillers in the ceiling and pseudo façade etc. with additional of stabilisers.

Careful extraction

Mud required for a structure can be  taken from the site itself. The top layer  of soil is the organic soil that is full of decaying leaves and fiber. Below it is sand and below that is clay. Organic soil is not used for construction. It is the layers of sand and clay that are suitable for extraction and yield mud for constructing walls etc. 

A damp-proof course 

Most mud constructions have an impervious material between the foundation and wall to keep it safe from water seepage. Technically speaking, 12mm thick cement plaster with waste engine oil or cashew shell is one option, and 120 micron HDPE sheet is another option to keep it dry and strong. Stabilisers like lime, plant juice, animal urine, chopped straw, sugar, gallnut sap, etc. alos improve stability and reduce the formation of cracks. Applying some oil to smoothen will give a mirror finish and two of more coats of cactus juice also make the surface water resistant.

Different methods

Cob is a natural building material made from sand, clay, water, some kind of fibrous material (straw) and earth. It is an inexpensive fireproof and earthquake- resistant building material. Cob is good for multipurpose use. It is particularly excellent for constructing curved or round walls.

Rammed Earth: This is strong and ideal for solid, squat, houses. This is a traditional mud construction technique that has been used in in Europe, China etc. since ages. It consists of using a mould with two parallel boards to compact the plain earth with adequate sand content inside them such that in situ wall construction is achieved. In this technique, wooden moulds are used with manual ramming using different types of rammers. 

Adobe: This is one of the oldest building methods which can easily cope with houses up to two storeys.  It is simply a mix of clay and sand mixed with water, In addition, chopped straw or other fibers are added for strength. Adobe is shaped into brick modules that can be stacked to form the walls. Normally adobe soil contains 15-30 per cent (maximum 50 per cent) clay as a binding material. Large overhangs are provided to protect the walls. It can be plastered over with cob or lime-based mixes for aesthetics as well as protection. It has good thermal mass, resulting in slow transmission of heat or cold.  

Wattle and daub: This is a method of construction that consists of a plain weave of vertically placed wooden stakes, and horizontally disposed of thin wooden strips (wattle). These interwoven elements are then daubed in a kind of plaster, made up of a variety of materials liked mud, clay, animal dung, sand, and straw. Wattle & daub is elegant and fine for building resistant structures in the seismic zones.

When the available mud is not suitable enough for construction, it can be used by altering its composition by adding stabilisers. Stabilising enhances the given property of the mud. It increases tensile and shear strength and reduces shrinkage. The most common and effective stabiliser is soil itself. Other indigenous stabilisers are:  straw/rice-husk/coir-fiber, plant juices, gum Arabic, sugar or molasses, cow dung, animal fat, etc.

— The writer is an architect based in Pune