The ever increasing population has created a global problem particularly in respect of food and shelter. In India, the housing problem is becoming severe day by day. As per estimates prepared by the National Buildings Organisation, the housing shortage in India is over 23.8 million units including 18.1 million in the rural sector. To prevent a slide-back in the housing situation, at least 17 million dwelling units would be required to be provided during the next four years thereafter. In the bleak backdrop of unmet housing needs, quick and economic construction of houses, preferably using indigenous materials is the prime need of the hour. Bamboo which possesses suitable structural properties can play an important role as a low cost material for construction in India. It can be used for making house-components such as trusses, rafters, roof grids, walls and ceilings. As bamboo plants attain maturity in a few years, it can be produced in a very short rotation cycle. At present bamboo is extensively used as a construction material in Japan, Malaysia, Indonesia, Philippines, China, India and other countries.
Why Bamboo is an ideal material for construction?
1. As compared to some constructional timbers, bamboos possess better strength and can thus be suitably used for structural purposes. Due to its physical form with nodes and cross partition walls, the bamboo-culm has a high strength to weight ratio. Hence it can make lighter but stronger structural components for houses at comparatively low cost.
2. The bamboo-surface as obtained in nature is smooth, clean and hard, enabling its easy use for specific purposes without any wastage.
3. Bamboo can be easily seasoned especially in the split form and treated with preservatives to increase its useful life.
4. The length, thickness and weight of bamboo culms are conducive to easy and economic transportation, storing and processing.
5. Treated bamboo strips of suitable sizes have been economically used for reinforcing mud walls, and also for cement concrete structures such as lintels, beams, slabs etc. commonly of smaller spans. Split culms plaited or arranged or woven in different forms and shapes can make good boards, mats and panels for light walling.
6. Because of their lightness, bamboo houses suffer very little damage due to earthquake. Temporary and quick construction is possible in case of urgent necessity in disaster-prone areas.
7. The non-magnetic character of bamboo makes it suitable for use in anti-magnetic structures.
Selection of bamboos for construction
1. Select bamboos of suitable species possessing the required structural properties.
2. Use only those bamboos for construction which are mature (at least three to four years old) and which have been or are likely to be felled when the starch content of the culm is at its lowest level (October to February in India). This will minimize insect attack.
3. Bamboos whose wall thickness is 9 mm or more should be selected for beams, columns and truss construction.
4. Choose straight culms having an almost uniform diameter of not below 8 cm to avoid fastening difficulties at the joints of the structures.
5. Bamboo culms selected for use should preferably have nodes or cross partition walls intact at both ends. They should be used alter proper seasoning and preservative treatment.
Depending on the availability and colt, the following species may be selected for house construction:
1. Dendrocalamus strictus - Available in deciduous forests and cultivated throughout Indian plains. Culms (5-15 m in length and 2.5-5cm in diameter) are generally solid and suited for structural use.
2. Bambusa tulda - Strong culm (6-20 m by 5-10 cm) suitable for construction of roofing and scaffolding. 3. Bambusa arundinacea- Culms (20-30 m bylO-20 cm) are thick-walled and often used for rafters, house-posts, tent poles, etc.
4. Bambusa polymoipha- Culms (15-24 m by 7-15 cm) available in eastern India and considered one of the best bamboos for walls, floors and roofs of houses.
5. Bambusa vulgaris- six 20 m in height and 5 to 10 cm in diameter, found is all over the tropical region, suitable for roofing and scaffolding.
Drying and Preservative Treatment
Drying and preservation are mandatory to make effective use of bamboos in construction for obtaining the desired strength and durability. Truss-joints etc. made with green bamboos will become loose due to shrinkage of the jointing members resulting in early weakening and collapse. Mature bamboo culms should be seasoned to about 12 percent moisture content. Bamboo has drawbacks as a building material due to its susceptibility to damage by insects, fungi, termites etc. Techniques for application of preservatives include brushing, spraying, dipping, hot and cold bath treatment, Boucherie method and pressure treatment depending on the facilities available at or near the construction sites. The use of preservatives and improved treatment techniques can ex- tend the service life of the bamboo structure to a considerable extent. One simple and mort common method to protect the freshly felled culms from beetle-attack and insect-infestation is to leach out the starch, sugars and other water soluble materials by submerging for three weeks in fresh or running water. Successful application of this technique has been reported from India, Burma, Fiji, Jamaica and other countries.
Bamboo is a renewable natural resource and has many of the properties of hardwoods that have been used in building and construction over the years. It can be used for housing just like any other building material. It has been used globally to build houses, especially in Asia, where they are in abundance. The recommendation made should be tackled to enhance the use of bamboo in housing to reduce the housing deficit and improve the livelihood of the people.
Source
Bamboos Current Research Proceedings of the Int'1 Bamboo Workshop, Nov 14-18, 1988 Know-how of Bamboo House Construction Harendra Nath Mishra Tituber Engineering Branch, Foi-est Research Institute & Colleges, Dehradun, India.