Built smartThere are many different measures for housing that are economically viable and technically safe
For post-quake reconstruction, Nepal needs to focus on proper housing techniques. Over 505,000 private houses were fully damaged and around 279,000 houses were partially damaged by the disaster. Appropriate cost-effective methods for reconstruction are a must, given that Nepal is a poor country. Thus, it would be wise to use local resources as well as ideas.
We need to analyse the stability status of the traditional houses first. The traditional houses are typically masonry ones made of locally available resources such as mud, stone, timber and tile and, in some cases, limestone. Usually, low-skilled workers who lack expertise are involved in the construction. The houses, though economically viable, are not well-built. The bond between stone and mud is not reliable, and with the repetitive effect of expansion and contraction in different weathers, it gets even worse. Moreover, the use of slates and tiles on the roof adds additional weight, thus causing instability during earthquakes.
So instead of building traditional structures, there are other different measures for housing that are economically viable and technically safe, which the local workers themselves can build. The first option is to build one-storey houses where possible. The height should be maintained equal to or less than three times the width of the base as this ascertains a stable structure.
However, while building a multi-storey structure, additional stability is required. So, horizontal bands may be provided, as these are the most important earthquake resistant features in masonry buildings. The bands are provided to hold a masonry building as a single unit by tying all the walls together, and are similar to a closed belt provided around cardboard boxes. Bands can be made of wood (including bamboo splits) or of reinforced concrete. There are four types of bands in a typical masonry building, namely gable band, roof band, lintel band (most important and provided horizontally throughout the side walls at a certain interval) and plinth band. The providence of lintel bands ensures safe structure (as was seen in Killari village during 1993 Latur Earthquake).
Timber houses too can be kept in view, as these are comparatively light weight houses that assure stability. Corrugated galvanised iron sheets can be used in the roofs. Mud can be used to cover both the sides of the vertical walls. Besides, the work can be carried out even by low-skilled workers. These kinds of houses have a comparative benefit of being economically efficient, architecturally versatile, and environmentally friendly.
Another option is the use of bamboos. Bamboos can be placed vertically along the side walls either on the side or in between the stone walls. Or, bamboos alone can be used with further coatings of clay plaster. Bamboos have better tensile and compressive strength than wood and nearly equal to that of steel. The bending strength of bamboos is higher than that of steel,which is quite an important aspect in earthquake resistant structures.
An interesting approach has been applied in Pakistan by a group called Pakistan Building Straw Bale (PAKSAB). They work to develop durable buildings which can be built with local resources, little money and are resistant to earthquakes up to 7.5 Richter scale as witnessed in the Kashmir Earthquake 2005. The main ingredient to build such houses is handmade straw. A simple jack system is needed to compress and tie straw-bales that act as building blocks.
Plastic bottle houses that are currently on the rise in African countries are another suitable option. The houses prove to be as strong as brick houses but have comparatively much lower construction costs. The mud-filled bottles act as building blocks which are bonded by mason sand and fly ash mix. The mix can also be made from mortar and clay, adobe, cob, sand or cement. This method helps in waste management and environmental protection too.
These are some of the methods that can be adopted for the post-quake reconstruction in Nepal. It is not necessary that a single option is adopted for the entire country. According to the means and resources, the optimum method for different regions can vary. The afore-mentioned methods have proven useful in various rural parts of Asia, South America and Africa. In the context of Nepal, it is not appropriate to choose the option of iron-reinforced concrete structures, though they are comparatively more stable.
Sharma has completed his engineering from Kathmandu University