by THE INTER-SECRETARIAT WORKING PARTY ON HOUSING AND BUILDING MATERIALS IN ASIA AND THE FAR EAST
IN Asia and the Far East, climate is the greatest single factor influencing housing design, which varies very widely in character. Consider, for instance, the difference in climate between the hot-arid areas of West Pakistan and Central India, the hot-humid areas embracing parts of the Indian sub-continent and the major part of Southeast Asia, and the cool or cold areas of the hill regions of the Asian mainland, of Japan and of Korea. The people everywhere have evolved their traditional houses and their methods of utilizing available materials to suit local climatic conditions, which naturally exert a deciding influence on the abundance or otherwise of organic building materials such as timber, bamboos and thatches. Only in the larger cities and towns are buildings to be found which may not be suited to the climate. There are a number of reasons for this but notably the feet that in some countries unsuitable design influences have been superimposed in the past and retained up to the present day, which originate in foreign regions of completely different climatic status.
Building construction in the islands of Indonesia covers a wide range of types, from the solid permanent structures introduced by the Dutch administration to traditional rural buildings, determined by the climate, and which have not varied much in character over the centuries.
The Republic of Indonesia lies across the equator. Although the islands are equatorial, temperatures are moderated by the sea and never become excessive. Hot nights and high humidity are however characteristics of the lowlands. Temperature is largely a matter of elevation rather than season, for the duration of sunlight on the longest and shortest days differs by only 48 minutes. In Djakarta, at sea level, the warmest and coolest monthly averages are within one degree, with the yearly average of 79° F. (29.1°C.). In contrast, Bandung at 2,395 ft. (730 m.) has a yearly average of 71°F. (22°C.), and Gede at 9,914 ft. (3,021 m.) has 48° F. (8.9°C.). Frost occurs only on high sheltered plateaus.
NOTE: The Inter-Secretariat Working Party is made up of representatives of the United Nations Economic Commission for Asia and the Far East, the United Nations Department for Economic and Social Affairs, the International Labour Organisation, Unesco, the World Health Organization, and FAO. Its last meeting at Bandung, Indonesia, 20-29 June 1956 was also attended by experts from the two regional housing research centers which are in process of establishment in India and Indonesia, to serve respectively the hot-arid and the hot-humid zones of the region.
For the future, the development of the building materials and construction industries will be closely tied to the economic situation of the country as a whole. A detailed examination has been made of the present situation and development prospects for cement and cement products, mortars, building blocks, steel, bricks and clay roofing, tiles, builders' hardware, coconut fibre and ramie waste, sand and gravel. But all these materials are mainly requirements for urban housing, and it is with the requirements for rural housing that FAO is likely to be most concerned.
As in most other countries of Southeast Asia, the dominating indigenous material in Indonesia is bamboo.1 Ironwood roofing shingles have been widely used in the past, although this material is now becoming rarer. Palm leaf and grass thatching is used throughout the whole archipelago. Perhaps the best traditional houses, and certainly the quaintest, are those of North and West Sumatra, with their high-pitched roofs whose gables are upswept to a high peak, forming a saddle-backed ridge.
1Reference is invited to:
F. A. McClure, Bamboo a, a Building Material, U. S. Department of Agriculture, Foreign Agriculture Service (Washington, D.C., May 1953),
"Industrial Raw Materials of Plant Origin. V. A Survey of the Bamboos, '' Engineering Experiment Station of the Georgia Institute of Technology Bulletin, XV, No. 18, (Atalanta, Georgia 1963).
There are 15 principal bamboo varieties throughout Indonesia, of which six are in abundant supply and commonly used. These are:
|
|
Height |
Diameter |
|
Bambusa bambos |
25 |
15 |
|
Bambusa vulgaris |
20 |
10 |
|
Dendrocalamus asper |
30 |
20 |
|
Bambusa spinosa |
20 |
12 |
|
Gigantochloa apus |
20 |
15 |
|
Gigantochloa venticallatta |
26 |
15 |
Preservation
The normal useful life of exposed bamboo components (untreated) in a building varies from three to five years in Indonesia according to the species, climatic factors and the structural design. Some investigations have been made into chemical preservation methods, but these methods have not as yet been applied on a large scale, owing to the expense involved. The standard method of preservation widely used in Indonesia and also in Burma and Thailand is to immerse the bamboo components, which consist of strips or plaited mats, in water for not less than one month. It is claimed that this simple process greatly reduces the susceptibility of the bamboo to deterioration due to insects and micro-organisms, which attack the comparatively soft internal fibres. While the scientific facts concerning this treatment have apparently not been published, it has been stated by competent construction authorities in Indonesia and elsewhere that bamboos subjected to it may last for 10 to 15 years.
FIGURE 4. Moluccas: A sago palm house. Timber frame, "gaba gaba" panels and roof of thatched fronds.
Construction
For rural house construction, "petting" is generally used for posts and frames (diameter not less than 9 centimeters) with roof framing of "andong" and tile laths of "petting" or "andong" (7 centimeters diameter for roof framing, and not less than 4 centimeters for laths and bracing). "Bambu apus" is considered suitable in small members of 4 centimeters diameter or thereabouts. Rural structures are usually tied together with lashings made from rattan, "aren," or bamboo rope. If done carefully, such connections will outlast the frames. In the best construction, bamboos are cut at node points, or if this is not possible, the open ends are plugged, to prevent the ingress of vermin. If in contact with the ground, bamboo members are customarily covered with "injuk" (the hair of the "aren" palm) and asphalted, to preserve them. It is, however, more usual to construct a raised l plinth of brick or stones on which the bamboo I frame is then built.
A common method of constructing wall and floor panels is known as "plupuh." These panels consist of halved and flattened bamboos placed vertically on and lashed or pinned to horizontal round members which are, in turn, fitted to mortices made in the vertical bamboo framing poles of the structure, or secured to form floor or ceiling. "Plupuh" is rather crude and is not weathertight in itself; in consequence, the floors of these panels are generally covered with closely plaited matting. External "plupuh" walls are similarly treated or finshed with plaster externally or on both sides.
"Gedek" is plaited from flattened bamboos l 2 to 3 centimeters in width. A loose weave is adopted if plastering is to be applied. The closer woven "gedek" is commonly used for walls and ceilings, walls being either whitewashed with chalk, asphalted and sprinkled with sand, or plastered. Ceiling "gedek" is covered with paper (2-ply) and given a wash of chalk or painted
"Gedek" is also commonly used as panelling for doors and windows.
"Kepang" is a finer-woven version of "gedek" and is generally applied without paint or paper finish. For external walls the hard bamboo skin is placed on the outside, and for ceilings this skin faces downwards.
Bamboo roofs
The simplest form of roof is constructed with halved bamboos running full length from ridge to eaves. Large diameter culms are split into two halves, the first layer being tied or nailed to purlins with the concave face upwards. The second layer is then placed over the first with convex face upwards, the whole interlocking to form a pattern rather similar in appearance to "Roman pattern" tiles. This roof is simple and can be made completely weather-tight. It is not, however, suitable in plague areas, due to the possibility of its harboring rats.
A sound roof can be constructed of bamboo shingles. These are cut from well-grown but still green culms of maximum diameter, the shingles being formed of split segments of 3-4 centimeters width. The length is determined by the distance between the nodes. A "hanging-split" is formed on the inside of the shingle at the node end and the tiles are fixed to split-bamboo battens by hooking this hanging-split over them. Shingles are cured by air-drying in the shade, to avoid the occurrence of splitting during the process. Tile battens are spaced on the rafters at approximately 15 centimeters apart and some 200 shingles are required to cover one square meter of roof. The minimum pitch on bamboo roofs, both halved bamboos and bamboo shingles, should be 30 degrees.
Plague prevention
In many areas of Indonesia plague is endemic and sometimes becomes epidemic. As this disease is carried and transmitted by rats, any construction is unsafe which harbors these rodents and from which they cannot be eliminated.
Bamboo construction is, therefore, totally banned in plague areas and in others it is permitted only if the construction details are such that the buildings will not harbor rats. This means brooking all open ends, closing ridge cappings, box gutters and cavities and using halved or segmental bamboo sections in preference to full rounds. Bamboo construction details of the type considered suitable for plague prevention have been prepared and are available free to home builders from the Department of People's Housing.
Research
Many authorities on the subject consider that for the greater part of Indonesia, and especially for Java with its highest density of population, bamboo is by far the most important building material. It is further felt that research should concentrate on methods of improving its properties and uses, rather than on seeking substitutes for this fine and versatile material.
A committee was set up before the second world war to make a study of bamboo, but was not able to make very much progress regarding cultivation, harvesting, conservation and constructional methods. Some tests are now being carried out on the mechanical properties of Indonesian bamboos when used as reinforcing material in concrete and on methods of impregnation for preservation.
Experiments were first made with split bamboo having toothed ends. The tensile strength was influenced favorably by increasing the length of the toothing. It was found that the shape of the teeth was also important. A second method consisted in splitting and looping the ends to form anchorages. These experiments have not yet been completed. Also being investigated as a possible means of achieving a pre-stressing effect is the use of bamboo strips which have been saturated in water.
Recent experiments with chemical impregnation have shown promise and results to date may be summarized as follows:
1. Pressure methods are successful only if the bamboos are pierced at the septums or if holes are drilled in the inter-nodes.2. In freshly cut bamboos (with leaves) conserving liquids are easily sucked up to a considerable height and in sufficient quantities.
3. Impregnation by immersion (preferably using Wolman salt) gives good results after 8 or 12 days.
The saga palm (Metroxylon sagu - Indonesian "sagu") is plentiful in Sunda (local designation "kiraj"), Java ("amblung," "kersula," "resula," "rembulung") and Madura (" bulung") Its trunk and leaves are very largely utilized for building purposes, particularly in the Moluccas, and apart from this its sago is a major item of diet, one trunk yielding sufficient for several months' food for a family. The palms grow in swamps and reach a height of 10 to 15 meters and a diameter of 60 centimeters in 10 or 12 years. The leaves attain a length of 1.0 to 1.20 meters and have a longer life as roof-thatch than most other palm leaves. The skin or bark is used for making rope or for plaiting matting or decorative wall covering (Indonesian: "tikar Bogor," mats from Bogor. The stalk ("gaba gaba"), after being trimmed to a length of some 3 to 5 meters and split, is placed vertically to dry out, during which process its weight is reduced from 0.8 to 0.5 kilograms per square meter and a specific gravity of only 0.25 is finally reached. When growing, the color of the stalk is light green; after drying it becomes a dark brown. The "gaba gaba" has the advantage of lightness and can thus readily be transported by road or by drifting down streams or along the seashore. Matured dry "gaba gaba" has a fairly good resistance to insect attack and if satisfactorily installed will last for 12 to 15 years in external walls.
For the construction of walls and ceilings, the halved stalks are trimmed to length, only the center portion of the trunks being used. The ends are then shaped to a 45 degree arris with a simple tool designed for the purpose. Two men can prepare between 20 and 25 pieces in an hour. The prepared "gaba gaba" is then placed vertically on the wall-framing, the arris ends being fitted into grooved girts top and bottom and the "gaba gaba" butted together vertically as snugly as possible. The whole panel is then fastened with bamboo nails and rope lashings. "Gaba gaba" construction cannot be whitewashed successfully but may be painted if funds permit. One hundred trimmed sticks are required for a wall or ceiling of 6 square meters.
FIGURE 5. "Plupuh": A much-used type of bamboo panelling
The Laboratory of Soil Mechanics and Roads at Bandung has been experimenting with rammed and stabilized wall construction since August 1952. The results to date do not appear very conclusive. The work is of interest in relation to experiments elsewhere, in that it incorporates pozzolano and hydrated lime in the soil mixes adopted.
A small house and numerous walls have been constructed with wall thickness varying from 4 to 8 inches (10 to 20 cm.) only. Some are reinforced with bamboo strips. The main difficulty encountered has been shrinkage and cracks in finished walls, no doubt due to an unsatisfactory soil mix containing too much clay and silt. The use of bamboo reinforcement is claimed as successful, although elsewhere it has not usually been found advisable to use reinforcement of any kind in this work.
The Australian Commonwealth Experimental Building Station recommends a minimum wall thickness of 12 inches (30.5 cm.) externally, and 9 inches (22.9 cm.) for internal partitions, and has developed an ingenious movable timber form-work with inbuilt wooden rollers, which greatly reduces the time taken up in placing and replacing shuttering The Laboratory at Bandung may well find it profitable to do further research along the lines already investigated in Australia and demonstrated on pilot schemes in Israel, India and Ceylon recently, but continuing with trass as a component of the soil mix. Its further development with lime as a stabilizing agent in rammed earth work will no doubt bring interesting results and a desirable reduction in cost, particularly for self-help projects in urban and suburban localities.
Indonesia's building development plans are considerably hampered at present by a shortage of foreign exchange.
A major improvement in domestic cement output is most essential as a first step towards urban housing development with a target of not less than one million tons per year. The building of plants throughout the archipelago to process coconut fibres, ramie waste and other organic materials into building boards, seems to be a desirable project.
The traditional methods of treatment and processing of organic building materials for housing, especially bamboo, require careful evaluation as certain local techniques - with slight improvements - may become generally applicable for low-cost housing. Methods for the increase of durability, retention of shape and reduction of seasoning period and of the cost should have high priority.
Efficient use of organic building materials and methods of construction are inter-related; they should be thoroughly adapted to each other and should be considered simultaneously. The gap between existing international knowledge and the practical application of experience by local builders is extremely wide in the case of organic building materials. Dissemination of such experience in practical and adequate form over all parts of Southeast Asia is imperative. The gap between existing international knowledge and its practical application can best be bridged by translating knowledge in the field through pilot projects. This approach should bring out with emphasis the advantages of implementing new practices.
