INTRODUCTION

Growing population: The world population reached 6 billion in 1999 and at the current rate and will have 7 billion people soon after the year 2010. The overwhelming share of world population growth is taking place in developing countries (89.9% in 1970-80; 92.2% in 1980-90; 95.2% in 1990-2000 and 97.6% in 2000 -2010). The population of developing countries has more than doubled in 35 years, growing from 1.89 billion in 1955 to 4.13 billion in 1990 (Karl, 2000).

Migration is one of the problems in developing countries. Rural underdevelopment encourages people to search for better opportunities elsewhere. The significant proportions of population increases in the developing countries have been absorbed by urban areas i.e. 83% in 2000-10. Urban settlements in developing countries are at present growing five times as fast as those in the developed countries.

Shelter as a livelihood: Access to safe and healthy shelter is essential to a person's physical, psychological, social and economic well being and is a fundamental part of basic livelihood. A safe home is a starting point for a family for further socio-economic development through social organization, education and employment It gives a feeling of security. Community relationship, which is the power and strength of any society, becomes stronger when people feel ownership in their house. However, greater numbers of population of the world lives either without or very temporary shelter. Poverty and limited access to resources have compelled to look for low cost housing options.

Housing deficits Poverty is a growing problem worldwide both in the rural and urban areas and impacts negatively on human settlements. At least 600 million urban dwellers in Africa, Asia and Latin America live in "life and health threatening homes" because of the very poor housing and living conditions and the lack of adequate provision for sanitation, drainage, removal of garbage and health care. Increasing number of urban poor are also homeless in both developed and developing countries with current estimate of the homeless population being over 100 million (Karl, 2000). At least one billion people do not have access to safe and healthy shelter and the number will increase dramatically with the population growth if the appropriate action is not taken (UNEP, nd). Housing deficit affects two millions only in Central America (Karina, 1998). In India, it is estimated that there will be a shortage of 39 million dwelling units (Mathur, 1987).

Housing deficit and environmental problems: The overwhelming shelter problem in the developing countries has resulted in the proliferation of slums and squatter settlements. This has a negative impact on the management of garbage, sewage and other sanitation problems affecting to people's health condition. This is also a main cause of environmental pollution in developing countries. Not only from environmental perspective, but also from scenic view such scattered temporary settlements make a city ugly and untidy.

Disaster management: Despite poverty and unprecedented population growth, natural calamity is another important issue to be dealt with. Every year vast majorities of global population suffer from various kinds of natural disasters viz. floods, landslides, earthquake, volcanoes etc loosing their houses, lives and properties resulting the breaking of social system and leading to an unstable life. Such disasters are very difficult to manage especially for the poor countries where limited economic and natural resources further deteriorates affected lives. Such reality has also compelled to think about options to re-settle affected populations in a short period of time and minimal cost to provide them immediate relief and to re-start their social life.

Bamboo Housing -

Bamboo has a very long history for its use in various purposes viz. Food, shelter, furniture etc. Bamboo has been serving humanity from cradle to grave in many countries since ages in many different and ingenious ways.

Bamboo is one of the oldest materials used for the construction of houses and other structures. As an excellent building materials it is relatively cheap, easy to work with and readily available in most of the countries where bamboo grows.

The importance of bamboo as a construction material particularly for housing has received a greater attention in recent years. In Asia, traditional bamboo houses of the low-income group use bamboo for supporting the structure. Even when other materials are used, bamboo forms a major part of the unit. Low cost bamboo houses are a cheap and safe alternative to the shelters of plastic, wood and stone that are currently being used by many homeless people. These houses are made from prefabricated and natural bamboo generally associated with other kinds of building materials like wood, mud, brick and concrete as per necessary so as to make house in different appearances and to increase durability.

The global shortage of housing materials especially in the developing countries is such that it warrants serious consideration. To keep pace with the population growth and to replace old houses, about 75 million units need to be constructed each year in Asia alone (Sattar, 1995). The short supply of timber and other conventional construction materials accompanied by rising costs make it imperative to increasingly use of bamboo for housing. The demand of low cost houses in Philippines from 1993 to 1998 was about 3.8 million units (Rebong, 1995).

Why Bamboo Housing?

Affordability: Of all the advantages of bamboo housing technology, the most important is its low cost that doesn't sacrifice quality, durability nor space. In stead it allows an option that is feasible for populations of scarce resources. According to PNB Costa Rica, bamboo houses are about 20% cheaper than the usual type of social housing. The cost of one house built by Viviendas del Hogar de Cristo (VHC) in Equador is less than US$450 which is pretty affordable for poor and marginal people. The government subsidy could further reduce the total cost for poor.

Employment generation: The manufacturing and distribution of low cost bamboo houses itself will provide employment to a range of people and there will be extra employment generation in its forward and backward linkages such as cultivation, harvesting, primary processing, transport and marketing of bamboo.

Availability of raw materials: Raw materials are easily and readily available in the bamboo growing countries. It has been calculated in the Costa Rican context that only 70 ha of bamboo plantation are sufficient to build 1000 bamboo houses per year. If these houses were built with timber, 600 ha of natural forest would be destroyed each year.

Adaptability: As the bamboo has been in use since long period of time in our society in one or other ways, this will not be very new for us. Bamboo housing is a self-help approach, which develops ownership and intimacy with house to the people.

Flexibility: It allows greater flexibility in designing and construction. One of the important advantages of bamboo housing is that it can be maintained regularly by replacing deteriorated parts. Application of traditional to modern technology in architectural designing is another benefit of bamboo.

Technology: It requires minimum technology. Most of the bamboo houses are based on exiting local technology, which doesn't require high-tech to construct. Its versatility offers multiple technological options for very economic to highly expensive buildings. It is also easily integrated with advanced technology

Quick to construct: Bamboo house takes very short time for assembling. Such efficiency makes it very important for disaster management and quick relief to victims or affected population to rehabilitate their family life. According to Viviendas del Hogar de Cristo (VHC), Equador, one bamboo house can be assembled in 4-5 hours.

Durability: With proper treatment bamboo provides service life of up to 30 years. Durability can be increased with careful choice of bamboo species, preservation, use of complementary construction materials and replacement of outdated or deteriorated parts in a regular basis. Corrugated and pre-fabricated bamboo are also widely used to increase durability and to increase resistance from damaging factors.

Safety: Due to lightweight and favorable elastic property of bamboo, its quality to resist earthquake pressure is very good. Gutierez (1998) reports that 30 houses that were in the epicenter of 7.6 magnitude rector scale earthquake survived without any damage in Costa Rica. Many of the concrete homes and hotels around them had collapsed but all 30 bamboo-houses remained intact.

Comfort: People prefer bamboo houses in the rural tropical areas where temperature is high in summer. In China, people still construct bamboo cottage to avoid heat and to enjoy cool air especially in the south of Yunnan Province. (Shensue and Qisheng, 1998)

Environmental benefits: This is a major consideration given in the recent years. Construction program should emphasize use of local materials, energy efficient designs and materials that don't harm health and the environment and labor intensive technologies that employ more people (UNEP, nd). Only bamboo can meet most of these criteria. Bamboo requires a little energy for the production of normal use of several building materials. Bamboo requires only 30 MJ/m3 per N/mm2 compared to concrete, steel and timber that require 240, 500 and 80 MJ/m3 per n/mm2 (TUE, website). Studies show that processing of bamboo requires only 1/8 of the energy that concrete needs to create a building material of the same capacity. In comparison to steel bamboo needs only 1/50 the amount of energy for processing (Roach 1996).

Control of deforestation: The rural housing in tropical developing counties still depend to a great extent on the availability of product products i.e. wood, thatch grasses etc. The depletion of forest resources and checks imposed on their harvesting have led to severe shortage of wood raw material and in some countries wood has gone beyond the reach of poor for building construction. In such case bamboo could be a viable option or alternative to replace wood. During disasters in developing countries, the general tendency is that affected people build temporary shelters nearby forest by cutting trees, which is environmentally and economically not a viable alternative. Bamboo could make viable substitute to control indiscriminate cutting of trees and to protect environment.

Sustainability: Social, economical and environmental sustainability is a growing issue of current developmental field. Bamboo has such a quality to meet all the sustainability criteria. It can be regenerated within 2-3 years, while that with timber could take longer than 25 years. It is the fastest growing plant of the world and replacement doesn't take longer time. Most of the locally available materials and tools can be sufficient enough to build simple low cost bamboo house.

Bamboo properties- Great advantage for housing

The mechanical properties of bamboo differ with species, age, climatic factors, moisture content and different heights of the culm.

The density of bamboo varies from 500 to 800 kg/m3. Bamboo possesses excellent strength properties especially tensile strength. Study shows that bamboo is as strong as wood and some species even exceed the strength of Shorea robusta and Tectona grandis (Sattar, 1995). An increase in strength is reported to occur at 3-4 years and thereafter it decreases. Therefore maturity period of bamboo is considered 3-4 years with respect to density and strength. The general mechanical properties of bamboo are (Purwito 1998);

¨ Tensile strength = 1000 - 4000 kg/cm2
¨ Compression strength = 250 - 1000 kg/cm2
¨ Bending strength = 700 - 3000 kg/cm2
¨ Modulus of elasticity = 100000 - 300000 kg/cm2

The important thing is failure in bending of bamboo is not actually totally failure. Due to its strong fibres, it first cracks unlike timber which breaks if bending fails. This quality of bamboo gives an opportunity to repair or replace failure parts of house. The elasticity of bamboo is better than wood for seismic resistant housing and as has been proved in the case of several small houses. One more advantage of bamboo over timber is that it does not have rays. Rays are mechanically weak therefore bamboo material is better in shear than timber material.

Key considerations for a housing project -

Resource availability: Availability of abundant bamboo resource of suitable species is pre-requisite for a low cost housing project. Natural stock is an insurance of the success of bamboo plantation in the areas for the future availability of raw materials. Inventory of resource and calculation of annual allowable cut is recommended to estimate availability of raw materials and to prepare bamboo management plan.

Tagert group: Target groups' interest and their economical condition are to be considered for the project. People might not be interested If abundant timber is available in the open access forest area. Secondly, such projects are likey to be successful in the community where people are poor and alternative resoruces are not available or not accessible to build the shelters. Community's traditional practice could be an useful information. If people are already using bamboo, it will be easier to work with them.

Cost: Cost is most important issue to be considered. The cost of bamboo house depends upon size of house, bamboo treatments, design, finishing, use of other materials etc. Therefore, It is necessary to know how much the community can generally afford for bamboo houses and how much subsidy is likely to receive from government. This will govern to decide the design of house for the community.

Enabling government policy: Government favorable policy is very important for the low cost bamboo housing. The experience of PNB Costa Rica indicates that large scale housing project is likely to be successful if government supports or endorses this in its housing policy. Enabling policy environment to support the shelter of poor peoples such as formulation of appropriate policy for subsidy, to facilitate their access to land, finance and low cost building materials are most important for the successful project.

(Compiled from various sources by: Shyam K Paudel, Associate Expert, INBAR)