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Report 5 of 5:
Bamboozled
- Colombia
Introduction
In Colombia, the poor build with bamboo while the better off build with cement. As a result of the earthquake in January 1999, vast areas of middle class housing collapsed, but the bamboo houses remained standing. Yet despite bamboo’s proven resilience to earthquakes, it still lacks credibility as a building material.
Bamboo grows to such magnificent heights and strengths that bamboo forests can produce enough 30 feet poles to build cities. To overcome the prejudice of bamboo being for "poor" housing, in Colombia, houses are being built to look like high quality surburban homes with thin concrete-covered wire mesh walls and tile topping. The difference is that the walls, first floors and roof are not supported by concrete but by strong and flexible bamboo that will ride out even the most violent earthquake. The attraction for the government is that a three bedroom house costs £1,000 which is half the price of a concrete one.
Harvesting and storage
There are about 600 botanical species of bamboo in the world. Bamboo is a giant grass which grows at a rate of 13 centimetres a day (nearly six inches). In six months, it will measure more than 10 metres (30 feet) and it reaches maturity within three years. It takes between four and five years for the bamboo stem, which is hollow, to become hard and strong enough to hold up a house.
Harvesting should be done in the dry season because the bamboo culms (trunks) have a lower moisture content, making transportation easier and reducing the chance of attack by fungi and rot. Once cut, the plant quickly grows a replacement stem. Only adult culms should be harvested because young culms provide food for the bamboo plant. It is important not to cut too many culms from the same plant, otherwise irreparable damage will occur and eventually the plant will die.
Bamboo should be stored under cover to protect it from rain and, preferably, clear of the ground. The ground must be clean, free of any rubbish and termites. Good ventilation is essential. Fresh bamboo standing vertically will dry in four weeks, and if it is lying horizontally drying takes twice as long. If drying occurs too quickly, the bamboo may crack.
Building with bamboo
Bamboo building is a simple technology which does not cause damage to the environment. It uses local materials, cut from the surrounding renewable bamboo forest, preserved with natural smoke. Nothing is wasted and nothing is imported, which means that local people can build with bamboo themselves and smoke their own bamboo in home made smokers.
Bamboo is an appropriate and aesthetically pleasing building material for an earthquake prone region. A bamboo frame keeps its shape very well in earthquakes because it is flexible and durable. Bamboo houses can be attractive, cheap and, if properly designed, long lasting. Weight for weight, bamboo is stronger than steel.
Although a house can be built completely out of bamboo (except for the fire place and chimney), usually it will be combined with other building materials such as timber, clay or roofing sheets, according to their availability, suitability and cost.
By joining bamboo together, a huge structure can be built. The bamboo is cut into hollow sections averaging six inches in length. To make a joint, a small hole is drilled into a single section which is filled with concrete and then a steel pin is inserted. The joint is fixed using another steel pin to the bamboo pole next to it. It is important to place the joint in a bamboo structure either at a node or as near to a node as possible. This technique can be used to hold arches or huge roof spans together. The cement adds strength but does not reduce the flexibility of the bamboo.
Preserving bamboo
Bamboo is an ideal earthquake proof material but it needs to be protected against insects. The insects attack the centre of the bamboo because that is the part that holds the most starch and sugar, so it needs to be treated. Bamboo used to be protected from insects by using chemicals imported from Europe which were expensive but now shavings taken from bamboo plants are used to produce a natural smoke insecticide.
Large smoke boxes, which contain bamboo ready-cut for building, are fired with bamboo shavings. These exude a natural pyrolitic acid which protects the bamboo against insect attack. Following this treatment, the bamboo will be insect resistant for 100 years.
Advantages of bamboo
- Bamboo is relatively strong and stiff
- Bamboo can be cut and split with simple tools
- The surface of bamboo is hard and clean
- Bamboo can be grown on a small scale
- The return of capital is quicker than wood
- Bamboo structures are flexible in storms and earthquakes
- Bamboo can be successfully used for the reinforcement of weak soil, for example, to avoid land slides or to strengthen a road.
Disadvantages of bamboo
- Bamboo has low natural durability and needs preservative treatment.
- Fire is a great risk.
- A bamboo culm is not completely straight, it is tapered. The nodes occur at different distances and the prominence of nodes can be a nuisance when the material is being worked.
- Standardisation is virtually impossible because of the variation in sizes.
For further information, please contact:
Technical Advisor
Intermediate Technology Development Group
Schumacher Centre for Technology Development
Bourton Hall
Bourton On Dunsmore
Warwickshire
CV23 9QZ
United Kingdom
Tel: +44 (0) 1788 661100
Fax: +44 (0)1788 661101
E-mail: infoserv@itdg.org.uk
Website: http://www.itdg.org/ |
Intermediate Technology Development Group would like to thank Paul Brown for providing the original article on using bamboo as a building material in Colombia. ITDG would also like to acknowledge Jules J.A. Janssen who wrote the original handbook "Building with Bamboo" ISBN 1 85339 203 0 which is published by ITDG Development Bookshop, 103/105 Southampton Row, London, WC1B 4HH, UK.
This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
Further reading available from ITDG Development Bookshop
Jules J. A. Janssen
Building With Bamboo: A Handbook
This revised handbook brings together the practical experience of engineers working in the field and research programmes testing the properties of bamboo. The book shows how bamboo has been used in different designs in developing countries and describes the varying properties and uses of different types of bamboo. The author shows how bamboo can be harvested, seasoned and jointed to form walls, doors and windows, roofs, ceilings, roof trusses and bridges, and how to weave bamboo.
The new edition updates and corrects the text of the first edition; and includes a case study of the extensive experience of Costa Rica in bamboo construction.
£9.95 1995 PB ITP ISBN 1853392030
David Farrelly
The Book of Bamboo: A Comprehensive Guide to this Remarkable Plant, its Uses, and its History
Introducing us to the oldest, most remarkable resource on the planet, ‘The Book of Bamboo’ is a practical and historical guide to this versatile wood. Both sustainable and plentiful, bamboo has been used for thousands of years to make a vast array of items- form basic necessities such as clothing and housing to more exotic and luxurious objects like acupuncture needles, sedan chairs and musical instruments.
£14.95 1996 PB Thames & Hudson ISBN 050027911X
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