Welcome to Adishakti

Hybrid Construction Technology and Adishakti

As in every activity that Adishakti, takes up, so also in construction, its attempt is to be a seminal space for new creativity and new knowledges. And as such, it tries to resuscitate old wisdoms and knowledge systems to address contemporary needs.

Adishakti's research into ‘vernacular' construction technology and the marriage of its findings with urban techniques has led to a hybrid construction technology, which was then used at the Adishakti campus. This research was led by Sreenivasan Vasthukam architect with Adishakti pictured below.

Below are given some of the processes, which were employed at Adishakti.

The Foundation:

This is one area where construction costs can inflate alarmingly. With the prevailing monsoon patterns, soil conditions in Tamil Nadu can be increasingly damp and slippery. During the monsoon there is constant topsoil movement (up to 3 feet) and unless the foundation is strong, cracks will begin to appear in the walls. That is why we have used the widely used Kerala technique –dry packing, which obviates the necessity for deeper piling and column foundation for additional strength.

Dry packing is simple and cost effective. Dig the foundation pit 2 feet wide and, depending on soil strength, 2 ½ to 3 feet in depth. Then fill in sand 1 foot high. Reduce this height ¾ foot by spraying water. This is the sand bed where the first bed of granite stones will be laid. The first layer of granite pieces is laid in a breaking line pattern. Each successive layer is filled with sand (mud can also be used). This process continues till the ground level is reached. When the gaps / hollows in the foundation are completely filled with sand, fill it with water and manually compress it with the feet. This will prevent cracks from appearing in the floor that is laid later.

The advantage is that both sand and granite are considerably cheap in this region and the clay content in the soil makes this foundation ideal for this part of Tamil Nadu. And it is highly cost effective—compared to the cost of building a conventional foundation. The conventional foundation costs Rs.60 per sq. foot, and dry packing works out to cost only Rs. 35 per sq. foot.

From here upwards the granite is bonded with cement up to a level of 1 ½ to 2 feet, to raise the construction above ground level. {This basement is very necessary in a mud construction as it lifts the mud walls away from the ground and prevents water from eroding them.}

Basement

Before starting the wall, the basement should undergo dampness proof and termite resistant treatment. For this a mix of cement, sand and used oil in a rich mix of 1: 3 is applied to the top of the basement on which the walls will stand.

The Walls

The country bricks available locally are of very poor quality and many builders use additional plastering to hide construction deficiencies. This inevitably makes the house hot throughout the year and consumes much more cement, sand and labor.

As a part of our research to find an alternative, we interacted with a number of old masons said to still possess knowledge of mud technology. We found that most of them knew processes for the rammed earth mud wall technology. Nowadays, mud walls are only used in rural areas, but by combing them with other urban and semi urban technologies we can employ them in towns as well.

Mud is needed in large quantities for the walls and it can be procured from the land on which the building will stand. First remove the topsoil up to 1 foot in depth. Then dig the pit to collect the mud, ensuring that all organic matter is removed from the soil to be used. The 1-foot depth of the pit makes it ideal for small houses built on 2/3 cents of land even in rural areas. The size of the pit will naturally depend on the size of the building. The dug area can then be converted into small ponds, which serve as excellent receptacles for water harvesting. And rainwater harvesting is even more necessary today because it feeds nutrients back in to the ecosystem and the soil gradually replenishes itself over the years.

After removing the soil from the ground it has to be studied for its clay and sand content. Too much of both are not good for the wall binding and can cause cracks to form later. One of the methods to check the soil is the “ Cigar Test “.

Roll and press the mud into the size and shape of a large cigar and place it overhanging a vertical edge. If the cigar breaks off when it protrudes 8 to 12 cm, the soil consistency is perfect. If it breaks off after protruding more than 12 cm it has too much clay. If it breaks off before 8 cm protrude, we need to add clay because the sand content is too high.

The next step is called “ Pazhuppikkal (seasoning) of the mud. After selecting the correct soil, it is thoroughly mixed with lime and lots of water, by using human feet. The lime to mud ratio is 40 chattis {trays} of mud: 1 chatti { tray} of lime. The lime acts not only as a binding element but also removes all termites. This mixture is allowed to sit for 5 to 6 days in a heap, well protected from the rain. Once the mix is dry, keep flaking off the top; which is the driest; to allow the damp lower parts of the heap to dry in turn, Thus you get the semi-powdered mix slightly damp, which is then ready for ramming into walls.

Next a simple test to ensure that the soil is ready for ramming. Take a handful of soil, press it together in your palm and drop it onto a plain hard surface from a height of 5 feet. If it gets pulverized into 4 to 5 pieces it is ideal for ramming. If it does not break then it has too much water and will lead to cracks developing in the wall. Before the ramming begins, 1 to 5 % of cement is added to the mix.

While the treated soil is drying the wooden moulds in which it will be rammed should be constructed. This is a critical step in this construction process. You can use any hard country wood like mango or neem, which does not bend and is less susceptible to moisture. The size of the panels can vary. The minimum length is 4 ft for a small building. The width will vary according to the size and height required. For a small house 1-foot width is enough. For a double-story structure the width should be at least 40 cm. The height of the mould in all cases remains 2 ft. Before starting the ramming add some cement to the mud mix which acts like a stabilizer. The ratio of cement added will vary from 1 to 5 % of the quantity of mud used.

Now begins the actual process of ramming the earth into the mould. It is the most crucial step in this process. For the quality of the walls depends directly on the strength of the ramming. The more forceful the ramming the greater the compressive strength of the mud and the stronger the walls.

Once the moulds are fixed, pour the mix in horizontal layers up to 4 inches height at a time. Now begin the ramming process. You need to maintain a leeway of 1 foot between the mud level and the ramming tool. Once the 4-inch layer is rammed pour the next layer and ram. This goes on till the entire mould has been rammed with the treated mud. After this the mould is removed and placed alongside the part just completed and then rammed with a fresh batch of the treated soil. Each mould takes just half an hour for ramming. One skilled mason is required for plumbing the wall. The physical ramming is done by unskilled labor. Nine moulds can be rammed in one working day.

The wall is thus built up in layer after layer of 4 inches each, and placed alongside the next section to be rammed. You can build only one course of walls in a day. The next day you can build on top of the earlier day's course. The walls can thus be built up to the required height, leaving appropriate gaps for doors and windows, with lintels or arches over the openings.

From the following day onwards the walls should be lightly sprinkled with water for the next 10 to 15 days to enhance the curing process. In the rains it is essential to cover the walls with adequate plastic sheets.

After curing for 15 days; using the above mentioned cement: lime: mud ratio; the mud wall will acquire a compressive strength of more than 30 kg per sq cm.

The Roof:

For constructing the roof we have used the tried and tested Filler Slab technique. It is highly cost effective and as it employs less cement-concrete, it is therefore cooler. For the fillers we have clay tiles, mud pots and scraped and varnished coconut shells. Lower income groups can use country wood or palm wood rafters with Mangalore tiles.

This particular foundation, the mud walls and tiled roof will resist earthquakes more than other building structures. The core strength of the foundation lies in its correct bonding.

Wall Plastering:

Wall plastering of mud walls can be done with the same mix of mud, sand, lime in the same ratio as when building the walls. And this is combined with the juice of a plant Trijada that is locally available. This not only strengthens and binds the mud further but is also an anti termite element. This mix gives a very polished and glazed finish to the wall plaster. Although bitumen can also be used it is bulky, expensive and environmentally unfriendly.

Alternatives to Trijada:

The crushed juice of the vegetable, known as ladies finger or the bel fruit or the hibiscus flower.
In Kerala, the braal fish is kept in a pot of water for three days until it becomes a sticky mass. This is an excellent binding agent. It also resists termite attack.
Burnt jaggery or liquid molasses is also a very good alternative, which strengthens the structure.
To avoid cracking on the wall, rice husks and small pieces of straw are added to the plaster mix.

All the above materials are easily available, locally. Traditionally, different binding materials are used all over the country. All the natural binders provide a smooth, lacquered finish that is both beautiful and strong.

To protect the walls from rain, the roof should have a sufficient overhang all around, which also provides essential shade for the rooms. Having a basement also helps. Over the plastered walls either a coating of wax or of varnish will protect them further against dampness.

The Flooring :

The floor is made with ingredients that are cheaply and easily available. For 1 kg. of this mix the following ingredients and their quantity is given below

Burnt and Powdered Coconut Shells I kg
Fresh Hibiscus Flowers 15
Gingili Oil 3 oz
Neelam ¼ kg
Kerosene Oil 1oz
Kajal 100 gm
2 kg white cement / Purified lime
2 kg black cement

Glazing powder [found between the tyre and tube] for shine. Earlier powder of soapstone was used; but masons in recent times have found this to be more efficacious.

The cost of this cool, durable and aesthetic flooring is Rs. 25 per square foot.

The burnt coconut shells provide the black color. They are more hygienic than oxide and there is no risk of infection. If you sleep on an oxide floor you will wake up with the side you are sleeping on, numb.

Hibiscus flowers have a binding quality and they too provide the black color. If you rub the flower in your hand it will get dark.

Kajal/Kohl again gives the black color.

Indigo gives the depth and shine to the black.

The Gingili oil is to cool the floor and to neutralize the 4% of coconut oil in the solution due to the coconut shells.

The kerosene is there to combat excess cool in the cold season. This floor is therefore cool in summer and warm in winter. One does not get arthritis or rheumatism on this floor.

In very hot regions like Andhra Pradesh purified lime is added to the solution for even greater cool.

Procedure

The coconut shells are burnt and then ground finely into the consistency of flour. Then all the ingredients are mixed with the water in which fresh hibiscus flowers have been kept overnight [the hibiscus flowers are also put into this paste]. This paste is prepared first on a grinding stone and then put into an iddli mixer so as to achieve a fine consistency.

Before the paste is applied to the floor a coat of sand and cement is used on it as temper. Then a coat of paste is applied. This coat does not have Kerosene and Kajal/Kohl.

The final coat of paste has all the ingredients. This coat is constantly leveled the whole day till there are no waves and unevenness in it. This is done till the paste dries and hardens. Then sand paper is used gently to remove the white smears on it. Finally the glazing powder is applied to it and rubbed.

The next day the floor is kept under water. After that it is waxed and polished. Then for fifteen days it is polished and rubbed with a dry cloth to cure it. This is done six times a day. Finally it is waxed again and a motor is used to polish it with the wax. In olden times the polishing was done manually with the flat end of a blade, which was rubbed vigorously over the whole floor.

After ten years when the floor needs to be cleaned: 100 gm of lime and 100 gm of soda bicarb [for 100sq ft] are mixed with 2 liters of water to form an acid. This is rubbed all over the floor with a cloth tied around a stick [because it is an acid]. Then the floor is washed with water and dried with a dry cloth. After this wax polish is applied on it.

The overall advantages of the HYBRID construction mentioned above are :

Highly cost effective. The minimum construction costs here even in the rural areas is Rs.400 per sq ft, while we have brought it to Rs. 350 per sq ft.
The materials are all locally available and can be replaced by alternatives in other parts of the country.
The construction remains cool in summer and is comfortable in the cool months.
The construction is eco- friendly.
A family of two with one mason can build a small house by themselves, with the advice and under the supervision of a single qualified structural engineer.
The finished building is earthquake resistant.
The construction is strong and combined with the dry pack foundation and fillers slab roof its endurance is enhanced.
The construction is aesthetically pleasing.

Dissemination :

Adishakti's construction experiments are impacting a large number of constituencies.

We have apprenticed masons from the two villages near us and from Kerala so that they can learn some of the technologies, which a few old masons in the region knew.
Our construction in rammed earth is leading the way for other local communities to follow suit particularly as the buildings are proving to be strong, aesthetic, cool and cost efficient. Already three such structures have come up in the neighborhood.
The Kerala masons have also absorbed this process and now are equipped to use it with understanding in Kerala. Our architect Srinivasan Vasthukam who is an engineer as well and who has lead the research is taking this process to Kerala.