changes in the use of building materials and products for low cost housing in the tropics

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This article was downloaded by: [The University of Manchester Library] On: 11 November 2014, At: 10:52 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Planning Outlook Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/cjep19 Changes in the use of building materials and products for low cost housing in the tropics A. E. S. Alcock a a Low Cost Housing and Town Planning Consultant , Published online: 24 Feb 2007. To cite this article: A. E. S. Alcock (1969) Changes in the use of building materials and products for low cost housing in the tropics, Planning Outlook, 6:1-2, 38-45, DOI: 10.1080/00320716908711416 To link to this article: http://dx.doi.org/10.1080/00320716908711416 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution,

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Page 1: Changes in the use of building materials and products for low cost housing in the tropics

This article was downloaded by: [The University of Manchester Library]On: 11 November 2014, At: 10:52Publisher: RoutledgeInforma Ltd Registered in England and Wales Registered Number:1072954 Registered office: Mortimer House, 37-41 Mortimer Street,London W1T 3JH, UK

Planning OutlookPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/cjep19

Changes in the use ofbuilding materials andproducts for low costhousing in the tropicsA. E. S. Alcock aa Low Cost Housing and Town PlanningConsultant ,Published online: 24 Feb 2007.

To cite this article: A. E. S. Alcock (1969) Changes in the use of buildingmaterials and products for low cost housing in the tropics, Planning Outlook,6:1-2, 38-45, DOI: 10.1080/00320716908711416

To link to this article: http://dx.doi.org/10.1080/00320716908711416

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of allthe information (the “Content”) contained in the publications on ourplatform. However, Taylor & Francis, our agents, and our licensorsmake no representations or warranties whatsoever as to the accuracy,completeness, or suitability for any purpose of the Content. Anyopinions and views expressed in this publication are the opinions andviews of the authors, and are not the views of or endorsed by Taylor& Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information.Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilitieswhatsoever or howsoever caused arising directly or indirectly inconnection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private studypurposes. Any substantial or systematic reproduction, redistribution,

Page 2: Changes in the use of building materials and products for low cost housing in the tropics

reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of accessand use can be found at http://www.tandfonline.com/page/terms-and-conditions

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Changes in the Use of BuildingMaterials and Products for Low CostHousing in the Tropics

A. E. S. Alcock

The observations and suggestions in this article are made in the light ofthe author's experience in the use of building materials and productsfor low cost housing in the less industrialized countries of the tropics inAfrica, Asia and Central America.

HOUSE BUILDING MATERIALS

The non-traditional materials which have so far made the greatestimpact on low cost housing in the less industrialized countries are iron,steel and Portland Cement. The building products made from these whichhave the widest use are corrugated iron, concrete blocks and reinforcedconcrete. These non-traditional products have invaded the low cost hous-ing field where previously traditional organic and inorganic materialsand products held sway. Of the organic materials such as leaves, grass,reeds, canes, bamboo and timber only timber has proved durable andsturdy enough to be acceptable as a building material under modernconditions. Of the inorganic materials such as clay, sods, laterite blocksand stone, only burnt clay and stone have proved durable and sturdyenough to be acceptable as building materials which meet modernstandards.

Corrugated Iron

One of the first invasions of non-traditional materials was made bycorrugated iron to replace organic materials for roofing and walling. Anexample of the replacement of traditional materials of low durabilityby corrugated iron may be seen in the hot humid forests of West Africa,where this product began to replace thatch at the end of the last cen-tury. Galvanized corrugated iron sheets of thin gauge came on to thelocal markets as soon as the planting of cash crops such as cocoa becamewidespread, providing money for the villager who previously lived bysubsistence farming and barter trading. The sheets were eagerly boughtby the people and used to replace the thatch on the roofs of houses builtof mud. The main advantage was expediency.

The corrugated iron sheets were easily carried as head loads from

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LOW COST HOUSING IN THE TROPICS 39

the towns and villages. They were easily laid on light supports. Nearthe sea the life of unpainted sheets was short, five to ten years, butinland they lasted for as long as twenty years. They did not seem to needmaintenance because of the galvanizing. They were fireproof althoughthis was not an important factor in humid forests where the fire riskwas low. They could also be used for catching rainwater, although tankswere expensive and mosquitoes bred in them and spread malaria.

It was soon found that houses roofed with corrugated iron werehotter and more uncomfortable to live in than those roofed with thatch.A few people put thatch over the galvanized iron sheets which kept thehouses cool and stopped leaking early in the wet season before theshrunken grass had swollen again. The humid climate was found topenetrate the exposed galvanizing, the iron rusted and then village roofsbecame eyesores. The rusting continued until the sheets leaked or wereblown off. In spite of these disadvantages expediency was still an attrac-tion, and faith continued in the galvanizing as the only coating necessary.The cost of initial and periodic painting was beyond the means of theaverage villager. In any case maintenance was what he sought to avoid.

Nowadays corrugated aluminium is replacing corrugated iron withdistinct advantages in comfort, appearance and durability, with theexception on hillsides that the glare from a neighbour's roof can bedistressing. Corrugated asbestos has even greater advantages in comfortand durability once erected, but costs are higher because of transporta-tion and breakage problems which the lighter and tougher metal sheetsdo not have. If however a local cement factory is established and localdeposits of asbestos can be mined at reasonable cost the way is open forlocal manufacture with a resultant reduction in the cost of asbestos-cement products.

Where the use of imported corrugated iron and aluminium has super-seded the use of traditional materials, the first stage in reducing thelocal cost is the establishment of a sheet corrugating industry usingimported flat sheet. This may be done in factories on a large scale butsimple machines hand operated (or power driven where electricity isavailable) can be installed in rural workshops. Rain water tanks canalso be made by simple machines which not only corrugate but also bendthe sheets to circular shapes. The use of machines for these purposes iswidespread in Papua and New Guinea. '

Squatters living on the fringes of the cities in the less industrializedcountries find it expedient to use corrugated iron sheets on the roofs oftheir shacks. The iron is kept in place by loading with stones. Whenordered by the authorities to move at short notice to a new site fartherout, the owners are able to remove the sheets intact and take them to newlocations. There are happier solutions to the rehousing of squatters butthese will not be discussed in this paper.

Portland Cement

Another of the first invaders of non-traditional materials was Port-

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land Cement which has brought more lasting advantages than corrugatediron sheets in the building of low cost housing in the less industrializedcountries. Where the art of burnt brick making is not indigenous theconcrete block has come into use for walling, replacing the traditionalmaterials of grass, leaves, bamboo and mud. But concrete blocks (oftenmade of sand and cement only) can be afEorded only by the few. The gapbetween the costs of new products and the old is too great to allowsweeping changes to be made from one to the other, especially in thepoorer areas of cities and in the villages. Therefore Portland Cementhas its limitations as a low cost material for housing. Methods of reducingthe cost of using Portland Cement while keeping its advantages includefirstly the establishment of a local cement factory wherever deposits oflimestone or coral and clay are suitably sited, and secondly the use ofmethods designed to reduce the quantity of cement per unit area ofwalling.

The employment of machines to compress and vibrate hollow con-crete blocks has made it possible to reduce to a minimum the amountof cement used. Nevertheless there are limitations to this process. Themachines themselves require power which is not available in manylocalities. The hollow blocks require sand and aggregate of good quality,which must be washed and graded and the mix requires expert controlover its cement and water content, as a high proportion of cement isneeded in the mix to ensure a satisfactory strength for the thin wallsand divisions within the hollow blocks.

The greatest success in using Portland Cement in low cost housinghas been as a stabilizer for mud. Not all mud can be satisfactorilystabilized with Portland Cement. Mud that shrinks and swells heavily ondrying and wetting is unsuitable. There are soils however that becauseof the nature of their mineral content do hot shrink and swell appreciably.These are the soils used traditionally in good mud building in thetropics and sub-tropics. Mud building here includes wattle and daub,cob, pise, adobe, sun dried brick and all processes in which soil orearth is used. In some countries particularly in North Africa and theMiddle East there are traditional skills in building with mud whichenable mud walls to last for centuries. The Greeks knew this. To quotePliny the Elder (in Natural History. Book XXV. A.D. 23-79) '• 'Have wenot in Africa and in Spain walls of earth, known as "formocean" walls?From the fact that they are moulded, rather than built, by enclosingearth within a frame of boards, constructed on either side, these wallswill last for centuries, are proof against rain, wind, and fire, and aresuperior in solidity to any cement. Even at this day Spain still holdswatch-towers that were erected by Hannibal.'

The pise technique is expensive because shuttering is needed. Thecob method, when an advanced technique is used as in Kano, NorthernNigeria, makes durable walls and roofs.1 The sun dried brick methodused by the ancient Egyptians also provides durable walls and roofs, anart which is being currently revived by the Egyptian Government.2

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The peasants of Egypt today know how to build good mud walls butthey roof these with thatch. Leaky roofs and the fire hazard make thatchan unsatisfactory material. Peasants are now being taught to buildparabo'lic mud roofs with sun dried bricks without falsework, in the waytheir ancestors did.

Mud buildings need maintenance in wet climates and the wetter theclimate the greater the maintenance needed. Without this they slowlydisintegrate. They are therefore suitable only for owner occupation.With absentee landlords and tenants in occupation, mud houses collapsein wet climates. As an example, social and economic changes in Ghanaenabled owners to build new houses in concrete blocks and lease theirold flat roofed mud houses. Every year in the past, the lime stabilizedmud coatings on the roofs were renewed by the owner occupiers andthe roofs remained waterproof. When this practice was overlooked by theabsentee landlords the roofs leaked and water softened the house walls.This led to the sudden collapse of many houses during the rainy seasonof 1953. These houses had stood for years—some a hundred years, underthe former care and maintenance of the owner occupiers and theirfamilies.

Building Sails in the Tropics

A belt of good soils for mud building exists around the world intropical and sub-tropical regions. These red and yellow soils, the laterites,are found on hillsides and not in valleys, where soils are degraded intoless suitable clays. Lateritic blocks are quarried in some places wherethe weathering process has gone on long enough to reduce the rock toa softer form, yet not soft enough to reduce it to loose soil. The blocksbecome harder after they are quarried and exposed to the air. Dr. F.Buchanan saw such blocks cut into bricks in South India in 1807 andcalled the rock 'laterite' from the latin 'later' meaning block. Lateriticblocks are also quarried in Ceylon where they are known as 'cabook'.They are used there for low cost housing, especially in rural areas. InEast Africa lateritic blocks and soils are known as 'murrum', while inGhana they are called 'swish'.

Lateritic soils may also be mixed with lime or Portland Cement, orboth, to form blocks of hard material not as strong as concrete blocksbut stronger than sun dried bricks. Because lateritic soils have a cohesivequality of their own: the quantity of lime, cement, or lime and cementrequired to stabilize them is less than that required to make the grainsof sand adhere together in concrete blocks. Generally twenty of soil toone of cement, as opposed to ten of sand to one of cement, for ordinaryconcrete blocks is adequate. Examples of extensive satisfactory buildingin cement stabilized soil blocks can be seen in Ghana where it hasbeen used in low cost housing estates, community development projects,agricultural buildings and village housing.3 Cement stabilized blocks havealso been used in Cyprus, Uganda, West Indies, Latin America andother parts of the world, but it is still not as extensively used as it

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might be in countries where its use would be an advantage. Thus, thereis a situation throughout most of the tropics, where many of the localsoils can at low cost be made into strong and durable blocks acceptableby modern standards for low cost housing.

The use of reinforced concrete has been fairly widespread in theless industrialized countries for many years. The techniques were oftenlearned the hard way, that is by the collapse of columns and beams,because they were inadequately or wrongly reinforced, or because thesupports were removed too soon. The placing of steel at the bottom ofcantilever beams instead of at the top has led to many failures. The carenecessary to get the steel in the right place adequately bonded to thesurrounding concrete, is not yet fully understood in many countries.Often aggregate, containing stones much larger than the maximum thatcan be properly used with the spacing and size of the steel bars, is putinto the formwork. The collapse of mushroom, fan or umbrella rein-forced roofs is not uncommon when first tried in less industrializedcountries. Yet if experience cannot be learned elsewhere it has to belearnt at home the hard way, and therefore one admires the efforts whileregretting the experimental failures.

The use of reinforced concrete in prefabricated units for low costhousing has been tried with varying success in many less industrializedcountries. To be cheap pre-fabrication requires a demand for a largenumber of units, a short haul and handling machinery. This has confinedits use mainly to extensive low cost housing schemes, to site manufactureof the units, and to places where lifting machinery from jacks to lightcranes and gantries can be provided. Even under the most favourableconditions prefabrication of reinforced concrete units has not succeededin undercutting the costs of more traditional methods, using bricks orblocks for walls, and iron sheets for roofs. Prefabrication has succeededin reducing the time factor which always has an impact on the financingof a project, in the reduction of capital charges during the constructionperiod.

Prefabrication in TimberThe use of timber for housing in some less industrialized countries,

where there is an ample supply, would seem to open the way to easyprefabrication of modular units for low cost housing. One of the mainproblems in timber prefabrication is the joining together of the pre-fabricated parts. Timber is not a material of fixed dimensions withinnormal moisture and temperature limits. It is apt to shrink and swellunder varying conditions of climate and even after being reasonably curedby stacking. Differences occur at junctions of prefabricated units. Take-uppieces may have to be inserted and other adjustments made, therebyusing up much of the labour saved by prefabrication at the factory.In highly industrialized countries such as Sweden, advanced techniquesof these problems. Such techniques cannot be too quickly learned andare used in the prefabrication of timber units which eliminate many

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used in the less industrialized countries, not only because of a lack ofexperience, but also because of a lack of ancillary industries to providethe necessary support for the prefabrication processes.

Traditional Building in Java

An example of the local production of pleasant, durable, weather-proof, sanitary houses, cheaply built, with only a limited use of non-traditional materials, may be seen in the rural areas of Java, Indonesia.4

In these regions the use of local materials and traditional techniquesfor building houses has been brought to a high standard of development.If not already made into building products by small family concernssupplying local markets, the products are manufactured by the housebuilders themselves. Bricks and roofing tiles are burnt from local clays.Lime is burnt from local limestones or corals. Timber is pit sawn fromforest trees. Bamboo is split and woven into prefabricated wall, ceilingand window panels known as 'bilik', and sand is dug for use with limein mortar and plaster. Stone is quarried for retaining walls and fordrainage and village water supplies. Pebbles are collected for cobblingfootpaths. Imported and factory made products are confined to nailsand hardware and a minimum supply of cement for foundations andconstruction work. Glass is sometimes used but is considered generallyto be a luxury. The walls are built of brick plastered inside and out.Window frames are top hung and covered with panels of 'bilik', whichhas the advantage of securing privacy, while letting in some light andbreeze through the small spaces which occur where the splines of bambooare interlaced to form the wall matting. When used as ceiling matting, thespaces in 'bilik' act as additional ventilators to the rooms allowing hotair to escape into the roof space and out between the overlapping dutchtiles. Roofs are high pitched to prevent the heavy rainfall from blowingunder the tiles, and the eaves overhang walls by three feet.

Much rural housing in Indonesia is built by self-help methodsespecially in Java. Community self-help and mutual aid through suchtraditional methods as 'Gotong Rejong'5 and 'San Batan',6 are usedto build all the houses in a village. Two excellent examples are thevillages of Tjiapus near Bogor in West Java which was rebuilt in 1961;and Torongredjo near Malang in East Java which was rebuilt in 1951.

Replacement of Traditional Products

In many countries manufactured roofing sheets and concrete blocksare replacing the traditional organic and inorganic materials for lowcost housing. Even local stone, burnt bricks, and tiles are replacedwhere they are either costly or of poor quality. There would appear to beopportunities for the improvement of local brick and tile manufacturewhere it exists, and for its establishment where it does not, if suitable clayand cheap fuel can be obtained. The lasting qualities of burnt brickand tile can be seen in the archaeological ruins of Egypt and the MiddleEast. The bricks of Babylon are today still in excellent condition after

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a life of 2,500 years. It can be safely assumed that well burnt bricks andtiles will have a durable life longer than would generally be expectedfor low cost housing. There is a field of study here for a team of plannersand persons in allied professions in the less industrialized countries inexamining the social, economic and technical aspects of improving orintroducing burnt brick and tile industries in their own countries.

The social aspects of self-help low cost housing, include comfortand health. Studies of how these aspects affect people living in similarhouses, under roofs of burnt tile and manufactured sheets should bemade. Physical factors such as temperature, humidity, and air move-ment may be recorded and related to local standards of comfort. Studiesshould also be put in hand concerning the investment necessary to bringthis about. If there is a growing ceramic industry making chinaware, thenopportunities exist for developing the manufacture, or improvement ofbrick and tile industries as an offshoot. Nigeria and Ghana are countrieswith growing chinaware industries. Where burnt bricks cannot be manu-factured economically for low cost housing because suitable deposits ofclay and cheap fuel are not available, then attention should turn tocement and/or lime stabilization of local soils, for building blocks includ-ing the manufacture of lime on a small scale in village kilns.

Stabilized Block Study TeamThere is also a field of study in some less industrialized countries,

to investigate the possibilities of using stabilized soil blocks for lowcost housing. The economies in making stabilized blocks are not only inthe low proportion of cement used but in the use of soils on or near thebuilding sites saving transport costs. Once the availability of suitablesoils is proved, the development of the use of stabilized soil is a matterof propaganda and education through mass media and demonstrationprojects. A civil engineer or an architect with some knowledge of build-ing research is needed on the technical side. A person trained in com-munity development is needed on the development side, to study thepossibilities of spreading the techniques of soil-cement block making,for low cost housing among the community.

The suggestions given in this paper for the revival and improve-ment of the use of local building products are made in the knowledgethat at any time, new factory products from the highly industrializedcountries may come on the market to replace the products already in use.Just as corrugated iron began rapidly to replace traditional materialsmany years ago. The new products must however, like corrugated ironsheets, be cheap, easily transportable and easily fixed if they are to succeed.In the meantime there are opportunities to develop local materialsfor low cost housing that may in the end produce more comfortableand better houses to live in.

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NOTES AND REFERENCES

1. Daldy, A. F. (1941), Temporary Buildings in Northern Nigeria. Public WorksDepartment, Nigeria.

2. Hassan Fathy (1964), An Ekistic Approach to the Problem of Roofing in PeasantHouse Building. Ekistics Vol. 17, No. 103, June 1964, pp. 391-398.

3. Alcock, A. E. S. (1958), Better Earth Building in the Tropics. Ekistics Vol. 5.30.4. United Nations Report of the Mission to Survey and Evaluate Self-help Housing

Methods and Practices in S.E. Asia. New York, 1963, ECN/11.5. Gotong Rojong—Community building or rebuilding of schools, religious build-

ings and houses. Participants, who all benefit, expect no reward in meals orceremonies.

6. San Batan—Mutual aid house building. Participants receive one meal a dayfrom house owners and there is a festive occasion to mark the completion ofthe houses.

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