Who can forget the killer Tsunami that hit the Asian coastlines on December 26, 2004? But from the resulting ruins, a sliver of hope shone through in Nias - a small island 120 kilometres west of the Indonesian archipelago. About 80 per cent of the modern houses on Nias collapsed but traditional houses remained standing.

The dancing island
Nias, lying on the fracture zone of the Eurasian and Indo-Australian tectonic plates, is shaken by earthquakes regularly. The regional architecture has many special elements that make buildings resistant to earthquakes. Like the foundations and the elevation with unique and complex arrangement of vertical and diagonal columns. If the buildings are maintained well they can last over generations and withstand strong seismic shocks. Even if damage occurs, the threat to life is not as high because the wooden constructions are light.

The Nias example is not the only one. Traditional houses in many regions are built to resist natural disasters - floods, quakes and cyclones. What structural techniques make these buildings so strong?

Kashmir

Earthquakes have occurred regularly over centuries in Kashmir and people have learnt to live with it. Two old construction systems known as taq and dhajji-dewari exist here side-by-side and both have tested quake-resistant features.

Dhajji-dewari: the name literally means a 'patch quilt wall.' This technique uses timber and bricks but is quite different from modern brick construction. A framework of timber is made which is then filled with burnt clay bricks. This creates a patchwork of small panels made up of brick masonry and surrounded by timber elements.

Presence of timber studs gives a sturdy framework and divides the brickwork into small sections. As a result the individual sections resist shaking and this prevents destruction of the wall. Dhajji-dewari system is often used for walls of upper stories, especially for the gable portion of the wall, even when the walls in bottom stories could be made of brick or stone masonry.

Taq: this system also uses timber and brick or stonework but is different from dhajji-dewari because it does not have any frames. Taq consists of heavy thick walls bonded together with large horizontal timber. The wood ties the walls together with the floors.

These traditional construction styles use clay instead of mortar, which gives elastic bonding to the brick and are well suited for the quake zones. The most recent trembler on October 8, 2005, once again proved this, as most of these houses escaped unscathed.

Kutch, Gujarat
Bhongas are found in the Kutch district of Gujarat. A bhonga is a single cylindrically shaped room, with a conical roof. The design technique is 200 years old. The walls are made of mud blocks while the roof is generally thatched. While locally available soft stone is chiselled into rectangular blocks for walls, timber and bamboo are used for roof.

Kutch has a very high earthquake risk and the circular shape of the wall helps to resist horizontal shaking. The roofing materials are generally very light. Even in case of a roof collapse its low weight ensures that the occupants are unharmed. The conical roof of a Bhonga is supported at its crest by a vertical central wooden post, which reduces the roof-load on the walls. Very few bhongas experienced any significant damage even in the area around the epicenter during the Bhuj earthquake in 2001 that measured 7.6 on the Richter's scale.

Floods, slides and quakes
We all know landslides are a regular feature in the Northeastern region. And Assam, of course, is chronically flood-prone. It is also a seismically active zone. People here have used the locally available materials like mud, straw, grass, reeds and timber to build their homes.

The most common type of dwellings is the stilted house built on a raised platform made from bamboo strips. Bamboo beams are placed diagonally, under the floor as bracing to reduce the sway.

A typical Assamese house differs slightly as it has a mud foundation. The walls of these houses are cheap and employ simple construction methods and are called ekra walls. A framework of vertical posts is set in the ground and split reeds or bamboo are woven to form a lattice. Mud is applied to this framework to make a thin wall. All the structures are tied together with ropes or wires tied to keep the unit together. Ekra walls have less mass and are flexible so they can survive earthquakes and cyclones.

Now let's take stock. These homes have helped us to explode some age-old myths.

Myth 1 - concrete buildings are stronger than those made of wood, mud or bamboo. Now, that is a hollow claim. After all people have used natural building materials since they began to build. Cement began to be used only in 1824.

Remains of the earliest villages that date back to 9000 BC, at Shanidar on the Turkish-Iranian border, show that the buildings were made of mud and reeds. Even today half the world's population live in houses made of locally available materials like bamboo, stone, grass, wood, lime and mud. Mud is the most widely used material. Different societies have used it in different ways and have given the techniques different names - adobe, chika, cob, sod, cajon and our own kacha. Mud houses are cool in summer and warm in winter.

Myth 2 - concrete is a modern and therefore better alternative.
We know that modern houses require a lot of energy to be made habitable. But apart from that a typical modern house has hidden costs too. To understand this we must see what goes into making one.

Burnt bricks, cement, iron, aluminium and marble are the most common construction materials. Each of these items consume enegy, as walls or roofs are made out of them. This is called the embodied energy of buildings. I have already told you about the high production cost of cement. Materials like bricks also require large amounts--for extracting and firing of clay. Transportation costs vary according to how heavy the material is and how far it has been moved. For instance, marble imported from Italy will have caused more energy consumption than stone bought from a local quarry. So the entire process - from production to utilisation - for each component contributes hugely to land, air and water pollution. It has been estimated that 22 per cent of green house gas emissions is contributed by the construction sector in India. Low energy materials are less polluting. So natural materials like timber, stone and mud will have low embodied energy and houses made of these have lesser running costs.

Old and new
At some point of architectural evolution, we seem to have forgotten the basic logic that was used to make the first houses. When design complemented the climate and the materials were easily and locally available. Some traditional and rural dwellings still preserve this logic. We can lern from that. But this certainly does not mean that we should completely revert to old forms of construction. What we need is a healthy mix of the traditional and the modern. A combination of old wisdom and new building science.

One way to reduce resource consumption and construct buildings that have less embodied energy is to use recycled materials. There are some new and very innovative experiments in using building materials like - straw bales, crushed concrete, telegraph poles and car radiators. The people of Tilonia in Rajasthan have experimented by using old farming equipment to build. Straw bales - a waste product of mechanical farming - is a cheap and low energy alternative. Just like the 'three little pigs', straw bales were used to build houses in the plains of North America more than a century ago. These houses still stand. The bales are waste straw that would otherwise be burned, adding to pollution in the air. But as building material they have low embodied energy and provide great insulation.

In India, the eminent architect, Laurie Baker, has used mud as primary material to construct new houses. He swears by mud, and insists that it can be used for large-scale mass housing schemes-as it can be found everywhere and is almost free.

So the housing planners will have to think afresh - think innovatively. And explore the old to find new solutions.

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