NBS BUILDING SCIENCE SERIES 100

Building To Resist The Effect Of Wind

VOLUME 5. Housing in Extreme Winds:

rTA— Socio-economic and

435 Architectural Considerations

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N0 ' UlTMENT OF COMMERCE • NATIONAL BUREAU OF STANDARDS

V. D

MH i e »7.; NBS BUILDING SCIENCE SERIES 100-5 -\ j\

Building To Resist

The Effect Of Wind

In five volumes O^JLiW/y. V

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VOLUME 5: Housing in Extreme Winds:

Socio-economic and

Architectural Considerations

Stephen A. Kliment, AIA

663 Fifth Ave.

New York, New York 10022

Under Contract to:

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

Sponsored by: The Office of Science and Technology

Agency for International Development

Department of State Washington, D.C. 20523

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued May 1977
Library of Congress Catalog Card Number: 77-600013

National Bureau of Standards Building Science Series 100-5

Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 100-5, 37 pages (May 1977)

CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1977

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

(Order by SD Catalog No. 03.29/2:100-5). Stock No. 003-003- Price $1.50 (Add 25 percent additional for other than U.S. mailing).
PREFACE ABSTRACT

This report is one of a five volume series describing

the results of a three and a half year research study to develop improved design criteria for low-rise build- ings to better resist the effects of extreme winds. The

project was sponsored by the Agency for International Development, Department of State. Volume 1 gives a background of the research activities, ac- complishments, results, and reccommendations.

Volume 2 presents a methodology to estimate design

wind speeds and a guide to determine wind forces. In Volume 3, a guide for improved use of masonry

fasteners and timber connectors is discussed. Volume

4 furnishes a methodology to estimate and forecast housing needs at a regional level.

This report presents information on the socio- economic aspects of low-income residential groups in developing nations subject to the effects of extreme

winds.

The purpose of preparing this information is to complement technical material developed as part of the National Bureau of Standards high wind project, by

identifying those cultural constraints which must be

understood if recommended practices are to become

acceptable and implemented.

The information contained in this report is the result of a broad-based search, review and analysis of

literature sources supplemented by interviews with

authorities in this field. Readily available source

materials are listed in the Appendix. Much of that material is of a highly technical nature, and has been

deliberately rephrased into simpler language in this report to make it accessible to decision-makers who

will be called upon to implement the findings.

Accordingly, illustrations, charts and tables have been

simplified.

The report describes the circumstances in the Philippines, Jamaica, and Bangladesh, the same nations that were the subjects of study under the high wind project. The author is indebted to the following individuals

who kindly contributed useful information and suggestions: Noel J. Raufaste, Jr., Richard D. Marshall and

S. George Fattal (National Bureau of Standards), John

Edmondson and Paul Campbell (International

Cooperative Housing Development Association),

Wallace Campbell (Foundation for Cooperative Housing), Ignacio Armillas, Giovanni Carissimo, Evner

Ergun, Alberto Gonzales-Gandolfi, Rafael MoraRubio, Mario Piche and Ludwig Van Essche (United

Nations Center for Housing, Building and Planning).

Typical socio-economic conditions in the Philippines,

Jamaica, and Bangladesh are identified. These conditions include strong respect for traditional materials and methods of house construction, and suspicion of innovative forms and approaches; a rising proportion

of urban poor who live in squatter settlements; and a rising ratio of inhabitants whose incomes are at a level where they cannot afford housing of any kind. The importance of land from a social standpoint is stressed. The report reviews the sites and services concept whereby low income persons are provided a

site equipped with basic utilities but must erect and

maintain a house upon it. Recommendations include: placement of buildings to exploit terrain; adherence to good practices in the configurations of the main ele- ments of a house (these are shown by means of simple

drawings); use of cheap, strong and locally available

materials.

Key words: Architectural design; housing; low income;

low-rise buildings; sites and services; socio-economic; structural design; wind-resistant.

Cover: Corrugated-iron roofed houses dominate this hur- ricane-prone Caribbean village.

in

CONTENTS

1. INTRODUCTION 1

2. GENERAL DATA 3

2.1 Socio-Economic Factors 3 2.1.1 Population Factors 4

2.1.2 Uncontrolled Settlements 5

2.1.3 Sites and Services 6

2.1.4 User Requirements 7

2.1.5 Attitudes to Prefabrication 9

2.1.6 Housing Economics 9 2.2 Housing Characteristics 9

2.2.1 Siting 9 2.2.2 Design 10

2.2.3 Construction Technique 10

2.2.4 Materials 12

2.3 Priorities 14

3. REVIEW BY COUNTRY 15

3.1 The Philippines 15

3.1.1 The Filipino Family and Their Housing Needs ?6

3.1.2 The Community 16

3.1.3 The Need for Housing 16

3.1.4 Economic Aspects 16

3.1.5 Housing Characteristics 17

3.1.6 Population Trends 18

3.2 Jamaica 18

3.2.1 Socio-economic Aspects - 18

3.2.2 Housing Characteristics 19

3.2.3 Housing Programs 20

3.2.4 Wind Patterns 21

3.2.5 Population Trends 21

3.3 Bangladesh 21

3.3.1 Socio-Economic Aspects 21

3.3.2 Housing Patterns 22

3.3.3 Housing Programs 25

3.3.4 Wind and Flood Patterns 27

3.3.5 Population Trends 28

4. CONCLUSIONS 29

APPENDIX-REFERENCES 31 Tables

Table 1 A Comparison of the Socio-Economic Characteristics of the Philippines, Jamaica and

Bangladesh 4

Table 2 Key Housing Characteristics in the

Philippines 17

Table 3 Population Trends in the Philippines, Jamaica

and Bangladesh (1975-2000) 18

Table 4 Key Housing Characteristics in Jamaica 19

v
Facing Page: A scene typical of the three countries covered by this report, where the population is predominantly rural.

In Jamaica, the ratio is 65 percent, in the Philippines 68 percent, and here in Bangladesh as high as 92 percent.
1. INTRODUCTION

This report is arranged in three major sections,

followed by an appendix containing 23 references. The first section is organized to include information

applicable across the board to the three nations where

the principal study effort took place. Factors such as population density and income are discussed as they

relate to housing quality, and the idea of uncontrolled

settlements is reviewed in terms of its benefits and

drawbacks. The same section also reviews housing

characteristics (such as siting, design, and choice of construction technique and building materials) from

the view point of how decisions affect the safety of houses under extreme wind conditions.

The second section reviews in greater detail the socio- economic characteristics of the three countries, and

relates them to physical housing characteristics. By

examining this relationship, the decision-maker is better able to improve the condition of building practices in each nation.

The third section evaluates the materials of the earlier sections and draws from them certain conclusions and

recommendations. Committed decision-makers can expand these recommendations as they plan and car- ry out programs to improve the resistance of housing

in extreme winds.

1
Facing Page: Blown-off roof and other building damage

point to need for improved building practices to better resist extreme winds.
2. GENERAL DATA

2.1 SOCIO-ECONOMIC FACTORS

Cultural patterns, socio-economic restraints and technical expertise (or lack of it) can both enhance and

be a severe barrier to innovation. Thus, understanding

a nation's socio-economic profile, the characteristics of its housing and its administration, is a vital factor

in improving current building practices.

The comparative socio-economic profiles shown on

Table 1 tell much. All three countries in this study,

Bangladesh, Jamaica and the Philippines have a high

population density. It ranges from 122 persons per km2 (317 per mi2

) in the Philippines to 525 per km2 (1360 per mi2

) in Bangladesh, one of the highest in the world. Compare this with the U.S. density of 22, and

that of the USSR, which has only 10 persons per km2

(56 and 26 per mi2

) respectively.

In these developing countries there is strong move- ment from the countryside to the cities. As a result the major cities in all three have teeming squatter towns.

3
Table 1 A COMPARISON OF THE SOCIO-ECONOMIC CHARACTERISTICS OF THE PHILIPPINES, JAMAICA, AND BANGLADESH

Philippines Jamaica Bangladesh

Population (million) 36.7 (1970) 2.0 (1972) 75.0 (1972) Population increase (per cent per year) 3.0 1.5 2.6 Density (persons per km2

) 122 174 525 Squatter population increase (percent per year) 12.0 N.A. N.A.

Percent of population in slums/squatter towns (percent) 5-6 N.A. N.A. Annual housing need (units) 100,000 (urban) 14,400 N.A.

370,000 (rural) N.A.

Urban population (percent) 32.0 34.5 8.0 Rural population (percent) 68.0 65.5 92.0

Average household size (persons) 6.0 4.0 N.A.

Typical number of rooms in household 2.0 (Manila: 3) 1.0

1 1.8

2 Number of persons per room 2.7 (median) 3.2 (average)

Note: This table is designed to give general comparisons only, based on analysis of available information. Survey

methods and frequency vary from one country to another.

1 Percent one room dwellings: 42 percent (urban); 25 percent (rural) [2 ].

2 Percent rural dwellings of one room: 53 percent [1 ].

In the Phil ippines, one person in 16 lives in squatter towns; the ratio as of 1970 was increasing at the rate of 12 percent a year. In Jamaica, squatter towns are growing (even though illegally). Information from

Bangladesh is sparse, but Dacca and other major cities are known to have extensive squatter populations.

Over and above all this, the populations have been

rising at a steady rate, from a low of one and a half percent per year in Jamaica (which has suffered emigration of its most skilled workers) to about two

and a half percent year in Bangladesh and slightly over three percent in the Philippines. Furthermore, even though infant mortality has been dropping and

lifespan rising through improved health care, citizens

in these countries tend to live less long than in developed nations and this has led to a very high pro- portion of youngsters under 15 years.

Tradition, combined with lack of schools, has forced onto housing such functions as day care, education

and play, for this high proportion of youngsters.

2.1.1 Population Factors

There are other ramifications to these population patterns. The economics of all three countries are highly

labor intensive, so that children are seen as an economic asset. Family planning efforts designed to bring population more in line with food and other

resources run up against this barrier, among others. This is especially true in rural areas where agriculture

is the main source of income.

Several other factors stand out strongly. Foremost is the tremendous over crowding in available housing.

In the Philippines, the average household size is six persons. The median number of persons in a room in the Philippines is 2.7. In Bangladesh, the average number is 3.2. It is traditional for several generations

(so called extended families) to make up a single household.

1

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To these factors one must add: shortage of funds,

markets not large enough to stimulate economics of

scale for prefabricated construction, undeveloped

transportation and distribution systems, a shortage of

skilled labor and, by and large, low standards of workmanship.

4
Furthermore, there is resistance by the various

populations to certain construction materials and

systems. A study carried out in Peru some years ago

used igloo-shaped houses made of polyurethane. The

houses were rejected because families were unhappy

with the lack of corner areas where one could put

things out of the way, predictably bad interior

acoustics, and a lack of normally defined property

lines in which to fence in animals. They were eventually abandoned.

of- occupy5

Most families cannot afford housing on the open

market and in many cases not even housing sub- sidized by the government. The percent of those who

cannot afford housing of any kind exceeds 65 percent

in all the three nations that were analyzed. Consequently, the very poor must rely on government

public housing programs (which are modest in all three countries) or build their own housing according

to demonstrably unsound wind-resistant practices.

2.1.2 Uncontrolled Settlements

Uncontrolled settlements, a term which covers bustees, squatter towns, and transitional communities, have come in for sharp comment as to their socio-economic

merit in developing countries. The two sides of the coin are painted vividly in an article by Mildred Schmertz (see reference 10). Citing a survey of squatters carried out in six Philippine cities by Dr. Aprodicio Laquian, the article notes that the

squatters "appear to appreciate their lives in the

squatter community. The urban squatter's friends, relatives and neighbors are there, the communities

are close to their places of work reducing transportation costs and time, and they have invested considerable time and money in their dwellings and

community facilities and services. Of great signifi- cance to them, of course, is the fact that as illegal occu- pants they pay little or no rent or taxes and such

amenities as they have are cheap. Laquian's figures

support his thesis that relocation techniques will not work unless the new areas offer better conditions

than those the migrant has already gained. . . ."

Yet, because "the non-taxpaying squatter is illegally

based, and because his numbers overwhelm the city's

public services, he does not have equal access with

other citizens to roads, public transport, piped water and drains and must depend upon himself for such

services. As a result, he has learned to expect little from the government and to view it cynically; on the other hand, the means exist by which his voice can be

heard within the larger political and administrative

arenas. The community organization to which he

belongs has members with access to politicians and

government officials at varying levels of hierarchy.

His cynicism, therefore, is mitigated by his own ex- perience of some degree of political effectiveness." The other side of this situation is much more devastating.

"Not all slum dwellers," the article goes on, "possess

the characteristics of the migrants just described . . . Criminals . . . and the indolent are found in every

slum. More common are those who are unemployed

or underemployed and have become adjusted to poverty, or for whom, ... it is simply inescapable."

"In the world's worst slums such as those of India and

Africa, many people are slowly starving. They are

apathetic, hostile, and suspicious. . . ."

Uncontrolled settlements:pros and cons

(see reference 23).

1. They provide migrants with housing at rents they can afford.

2. They serve as a reception center for migrants,

helping them to adapt to urban life.

3. Within their own society they are a source of

jobs in small-scale and marginal enterprises.

4. They provide accommodation at a reasonable

distance from sources of jobs in the adjoining

town or city.

5. The communal organizations provide support

during unemployment and other difficult times. (A study by a Presidential Council on the Squatters of Manila, the Philippines, found, in a squatter community of 2,625 families, 29

organizations, with 65 percent of family heads

interviewed belonging to at least one organization.)

6. They encourage (and reward) small-scale pri- vate enterprise in the field of squatter housing.

7. In many cases, they provide their own security

system of a caliber that Government would find very costly to furnish.

8. Some planning professionals question the

5
merits of uncontrolled settlements, due to the

public health, educational, family health care, circulation and other problems which these set- tlements find hard to solve. The absence of

"sites and services" aggravates these conditions.

4.

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Four fallacies: Four fallacies of thought have arisen around the squatter town problem:

1. The more squatter settlements are improved,

the more migrants are attracted to them.

Response: Social and economic stimuli will continue to attract migrants to urban areas no matter what the living conditions.

2. Improvements in rural areas can significantly

reduce migration to urban areas (see reference

14). Response. Without urbanization and in- dustrialization, there is little prospect of rural development. The real question is: how is it possible to prevent the exchange of rural poverty for urban misery?

3. Decentralization of urban growth will reduce

problems of urbanization (see reference 14). Response. Large scale capital investment in a number of rural areas designated as growth

centers, may tend to attract migrants to relatively small towns which, at least in the

short and medium term, would [lack] the fi- nancial and staff resources for providing community services, and otherwise dealing with a rapidly growing population.

Squatter settlements are homes largely for rural and uneducated groups.

Response: Squatter settlements vary widely.

Residents of some are close to their rural backgrounds. In others, there is a notable proportion

of professionals, such as engineers and doctors. MP

2.1.3 Sites and Services

A policy that is becoming more and more accepted is to improve squatter settlements by providing si'fes and

services. Land, water supply, electric power and waste

disposal are provided. Unsteady buildings are replaced by better structures with appropriate help as the settlement becomes more established. This way,

self-help is stimulated. A key move from a public planning standpoint is to incorporate the sites-and-services concept into municipal or regional zoning programs. Types of sites and services:Following are four forms

of sites and services (see reference 19).

1. Subdivide land alone—only an unimproved

building lot is provided.

2. Subdivide land and install basic public utilities and some community facilities.

3. Subdivide land and add a full complement of public utilities and community facilities.

4. Install a combination of public utilities and

community facilities in existing residential

areas. An interesting variation on the above are the po/esof

India. An entire downtown block owned by the Government is leased to a private individual or company, which then rents space to transient occupants.

The block is entered only through a guarded gate, with rent collected weekly. Temporary structures in- side the walls serve newly arrived migrants who are

close to work and temporary job sources, and have

the opportunity of acquiring more permanent jobs

and housing.

Hierarchy of public utility services: As the sites and

services concept evolved, a hierarchy has emerged

among the public utility services a government may

provide.

6
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In the top category are water supply and waste

removal, since lack of purity in the one and improper

location and design of the other are the primary

causes of disease and mortality in squatter settle- ments. Water and waste lines, if linked to a sanitary core, constitute a minimum standard.

Wift s<uvi lac^ »r

In the next category are utilities such as electricity and

public lighting, sidewalks and paved roads, gas and

telephones.

Public utilities make up one of three components of the sites and services concept. The other two are community facilities (or access to them) and the land itself.

The importance of land:From a public health standpoint, the need for proper water and sanitary systems

is uppermost. From a social standpoint, it is the

security of land occupancy or ownership. Most

families, given technical assistance, will find a way to erect a dwelling, so long as they can count on security

of land. To lower the cost of land for the occupant, a variety of arrangements is possible. An approach tried in Jamaica offers a 40 year leasehold on land at a modest

rental; this is renewable for 40 years more. The lessee

is responsible for erecting housing and paying for

utilities. The only subsidy is in the form of technical

assistance. The importance of jobs:Work, its presence and access

to it, is a major force in the life of the squatter community. This concept was the central theme of a design proposal that won for Ian Athfield of New

Zealand the first prize in an international competition to design a master plan and new town on a site called Dagat-Dagatan—for eventual resettlement of 17,000 families living nearby on Manila's abject Tondo

Foreshore (see reference 10).

Athfield's scheme makes the workplace the major

controlling element of the design. It would be the first part of each neighborhood unit or barangay to be built, initially along its periphery. An area within each

such a working periphery would control the supply,

manufacture and use of building materials for erecting

housing. Space within the periphery would also be

leased to private light industry to create further jobs.

2.1.4 User Requirements

Research into user requirements on low cost housing can help evolve designs that are both technically ade- quate and also meet socio-economic needs. Clearly, since most current designs for low-cost housing do not meet proper wind-resistance criteria, new designs,

quite possibly using unfamiliar building materials and

methods, will have to be used. As there are no hard

data on user acceptance of new designs, this information on user acceptance must be sought out.

Dr. Tarja Cronberg (see reference 15), used these sources of information: statistics of the country's

population (death rate, size of families, average in- come, etc.); interviews with local builders, architects,

and construction workers; and observation. She

divides the information into two classes: user characteristics, and user activities. Under user characteristics, she identifies the users' typical physiological and psychological characteristics, plus such socio-economic characteristics as family size and structure, mobility, identification with a particular ethnic, religious or geographic

7
group, and educational background.

Under user activities, Dr. Cronberg identifies nine

categories:

• Sleeping

• Food preparation

• Storage

• Personal sanitation

• Work

• Recreation/play

• Social (receiving of guests, etc.) • Identification/participation • Learning and orientation

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She concludes that more information is needed in four areas:

• Health standards in existing environments.

• Need for personal space and privacy in over- crowded housing.

• Social activities in the neighborhood and community.

• Activities of specific groups such as children.

This determination, to be done with the aid of local experts, is clearly important in arriving at a clear, objective set of criteria of how families in a given milieu

are likely to respond to innovative, wind-resistant

design that is new or unfamiliar. The Cronberg study also indicates that innovative

housing designs and new materials are widely ac- cepted in the Philippines, even by low income

owners. This is true especially where the owner is able to make small individual changes on his house

after he moves in. Most practicing architects and

engineers in the country generally accept new

materials which have the needed properties and if the

cost is reasonable. The opposite has been the experience in Peru. Peru is not a part of this report, but is a useful object of study

nevertheless. New construction materials usually are

initially rejected in Peru; only a few have survived

this reaction and managed to keep a place in the market (see reference 15). Examples of building pro- ducts that have been rejected include:

• A hollow block based on a Swiss patent and

made up of mineralized vegetable fibers encased in cement.

• A panel-sized product made of expanded gyp- sum.

• Corrugated sheets of glass fiber and polyvinyl

chloride (PVC); plastic bathtubs and basins. • Sprayed polyurethane igloos developed in Germany for use after earthquakes.

The few construction materials (other than in- digenous materials) that are broadly accepted are cor- rugated sheets of galvanized steel and asbestos ce- ment. The former, despite poor thermal and acoustical properties, are popular because they are strong, are light weight, and can be easily and cheaply

transported on the backs of mules. The latter, though

superior in thermal and acoustic terms, are quite fragile, the resulting higher breakage also drives up costs, and are carcinogenic.

8
2.1.5 Attitudes to prefabrication

Another Peruvian study with lessons for other developing countries is a 1962 survey of public at- titudes towards prefabricated housing. It was carried out by students at the Architecture Department of Peru's National University of Engineering.

Consumer interest was found to be low because

prefabricated houses cost only a little less than site- built brick and concrete houses and a good deal more

than adobe houses; they looked too uniform; and the

public did not appreciate the savings inherent in the shorter construction time. As for builders, they found

that a restricted market led to high sales/costs; financ- ing was difficult; and complex transportation sharply

raised construction costs outside the immediate area

of Lima.

In the Philippines, for example, demand for new

dwellings would require a capital investment about

5.7 percent of the gross national product; in fact, in 1967 only 2.8 percent was so invested.

5.7%

2.8%!

Yet the sites and services solution referred to earlier ha

been found desirable, especially in the Philippines,

where self help (known as bayanihan) is widely ac- cepted in the building of dwellings. It is discussed in greater detail later in this report.

2.2 HOUSING CHARACTERISTICS

Four ingredients of housing are discussed. These are:

siting, design, construction methods, and materials.

2.2.1 Siting

Little regard has been given to the placement of houses in relation to danger from winds. Good site location or orientation linked to local terrain and

natural cover can be, but usually has not been, deter- mined from historical wind data. This data provides

the frequency velocity and direction of the prevailin

winds, especially in their extreme form. Hence,

windstorm damage can be reduced by placing build- ings so they are protected by hills, stands of trees and

other natural elements.

2.1.6 Housing economics

Housing approaches in developing countries have

been criticized on two grounds. First, housing deficits are computed without taking into account the values

or preferences of those to be housed. Secondly, the

traditional solutions to housing deficits have turned

out to be well beyond current capital investment

rates. Even in countries that anticipate a high rate of economic growth, the competing demands of

agriculture, industry, and other programs reduce the funds available for housing to a level far below needs

(see reference 15).

The concept of landscape and terrain as a factor in wind resistant design has been formally established i the British Code of Basic Data for the Design of Building

In introducing the concept of the topography factor, that is, of classifying varying degrees of ground

9
roughness as a wind design determinant, the code

recognizes four categouries of terrain:

• Long stretches of open, level or near level, country with no shelter; • Flat or undulating country with obstructions,

such as hedges, scattered windbreaks of trees and oc- casional buildings; • Surfaces with many large obstructions, such as well wooded parkland, small towns and the suburbs

of large cities; • Built up areas with a general roof height of above 25 m (82 ft).

2.2.2 Design

It is possible to make buildings more wind resistant by

improving connection details, by learning more about

the effects of wind loading on buildings, and by

avoiding certain shapes or groupings of buildings so as not to cause undesirable aerodynamic effects. To those

ends, theoretical as well as experimental wind model

research is currently being conducted.

Certain design elements can reduce wind resistance. Sharp edges, low-pitched roofs, large overhangs and

improper grouping of buildings will cause problems.

The aerodynamic behavior of buildings can be improved by providing rough surfaces or ribs on the exteriors of walls. Grass roofs have allegedly served to relieve pressures, as have smooth transitions between

building surfaces (see reference 15).

ixneaHi fount itrionS

Wind,

Unfortunately, the internal pressures developed in buildings with openings are usually not considered in design. Roof failures have been caused by wind which

penetrated the structure and pressed up on the roof from beneath.

internal prHSui^b

Certain configurations (such as cylinders, and iglootype structures), are far more stable than box-like

structures, but in the few places where they have been

tried the cultural attitudes of the population caused

them to be abandoned.

In Bangladesh, various building designs were tried using materials and shapes new to the country. These

are integrated roof and wall elements, made up of units consisting of polyester resin and jute. They have

performed well in wind but their final social acceptance is still unknown.

2.2.3 Construction Technique

In developing countries, it is often hard to separate

design from construction. By and large, typical

characteristics can be summarized as follows:

Characteristics—foundations, walls and roofs:

1. Foun- Load transmission to soil becomes

dations. less critical since low- rise dwellings of one or two stories do not generate a high dead load. Where

flooding is not common, rectangular

footings of plain or reinforced concrete

or gravel are used. In flood-prone

areas houses may be built on stilts (e.g. bamboo) driven into the ground to the appropriate depth. Mat footings are sometimes used on unfavorable soil.

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10
Walls. Walls are either structural or nonstructural. When non-structural, they

merely serve as an in-fill for a frame

and their contribution to the overall

structural resistance of a building to wind pressure should be minimal.

Structural walls of wood, concrete, burnt clay or soil-cement composition

are the most common in low-cost housing construction. Walls are either monolithic or small unit masonry type,

where units are laid in staggered

courses, usually in beds of mortar. Clay

brick and tile, adobe brick and concrete block are the most common masonry

units. Quality control in making these

units, as well as the mixing of the masonry mortar bed, can make or break the structural strength of the

total wall. Wind stresses on walls are either out- of-plane bending or in-plane stresses. Out-of-plane pressures (when wind

acts directly at right angles to a wall) cause deflection and eventually failure. Tornadoes common in Bangladesh

have pressure drops so strong and sud- den as to actually pull walls outwards.

couuse raj/urfr or uaL>

In-plane stresses are developed in walls which act as shear-resisting elements within the building, the plane

being parallel to the wind direction.

Moreover, incorrectly planned wall openings may be critical, especially at corners. In any case, conditions where

two walls intersect or between walls and foundation or walls and roof, re- quire special design due to the high

stresses at those joints.

3. Roofs. Roof pitch is an important design ele- ment for good wind resistance. The

magnitude of positive or negative wing

pressures on roof surfaces is directly related to roof pitch. Wind affects roofs

in two ways, direct and indirect.

Crates 1^W4r*>

Direct local effects are made up of high

positive or negative pressures over

local areas of the roofs. This may lead

to damage to roofing—whether

shingles, tiles, corrugated sheets, etc. Overhangs, common for sun protection, are especially liable to wind

damage, as they undergo positive pressure from below and suction from

above.

Indirect effects occur when wind loads are transferred to lateral walls, causing

stresses. If this mix of pressures on the roof is strong enough, the capacity of the connections will be exceeded and

the roof will be lifted off. This brings

additional danger since every roof has

a structural role as a horizontal

diaphragm. This diaphragm behavior

of the roof transmits windloads from

the front to the side walls. If a roof is blown off, both frontal and lateral walls may collapse due to loss of such

diaphragm stiffening.

77
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roof ^own •

Flat roofs (especially with overhangs)

are more subject to wind damage than

roofs with a steeper pitch.

2j0

<X8

4f h&jhrMd, roof pitch.

Prefabrication: Any method that will produce housing more effectively must, at least in its first phase,

make the best use of available local labor.

In the Philippines, few companies make prefabricated

components; those that do are private firms producing wall panels and roof trusses, and a government

firm which makes lightweight concrete panels.

Filipino builders are said to recognize the savings

which prefabrication offers, and feel they can make it work. Their problems at present are lack of adequate

financing and too small a volume.

In Bangladesh, reinforced concrete shell roofs in the shape of a hyperbolic paraboloid have been used,

using 25 mm (1 in) pre-cast reinforced concrete ele- ments, with concrete connections made on site.

In Jamaica, the most common form of industrialized construction consists of large precast concrete panel

systems. Wall and roof panels are lifted and

assembled by crane. Other forms of prefabrication in Jamaica use precast posts combined with precast concrete or timber beams, with concrete infill panels be- tween posts.

Two technically creative projects are underway in the Kingston area. The Portmore development in St. Catherine was planned to produce 30,000 houses and

one-third of these were completed by late 1975. The

cast concrete construction system consists of large concrete panels, cast in fiber-glass molds, erected by

the vacuum lift process and interconnected by welded

anchor plates. Structural elements vary from solid concrete to ribbed panels, with a minimum panel

thickness of 38-mm (1-1/2 in). The developers (and

builders) of the system, West Indies Home Contractors

Ltd., claim to be able to produce 15 units per day (five units of three different houses), from one precasting

yard and factory.

The other project consists of houses in Kingston

designed by U.S. architects Baker/Grinnell as pro- posed for government-sponsored low-income housing. The system (a prototype has been built on site), consists of gypsum and bagasse panels—a locally available particle board made of sugar cane fibers

and a treated paper honeycomb core. The panels are produced on site by a lightweight portable machine

which has its own power supply. When it is operating

at full capacity, the developers claim the system can

erect up to 50 houses per week from a single fabricat- ing unit. The structure of this house has been reviewed by the New York structural engineer Paul Weidlinger, who

said the house would resist winds of 53 m/s (120 mph)

under extreme conditions of pressure and suction,

assuming open windows. The earthquake resistance is for a zone three shock (Jamaica is in zone two).

2.2.4 Materials

Following are common materials used in the three nations:

Soil: Natural earth is about the most common

material used. Sun dried adobe bricks have been the

basic masonry units for low-cost housing. These bricks are often untreated against penetration by water.

12
More recently adobe brick has been stabilized by the addition of asphalt. This boosts the durability and

water-repellant properties and is a major

breakthrough. The social image however, of adobe,

stabilized or not, is still not high.

Wood: Wood, while popular, easy to handle, versatile and strong in tension, is not available every- where. It is useful as a framing material. When not

available in milled, dimensioned form, it is replaced

by non-dimensioned lumber—as cane, bamboo, palms

and thatch for structural enclosure and roofing pruposes. Cane, bamboo or split wood are often used to reinforce adobe masonry. Major draw backs are moisture, fire and insect infestation. Chemical preser- vatives which are produced in developing countries can prevent this kind of danger and deterioration.

Also, chipboard products are used for walls and ceil- ings.

Concrete: Where sand, cement, water and various

additives are plentiful, concrete is a logical and

widespread local building material. Weak in tension,

it can be reinforced by a local material such as bamboo

as well as by costlier imported steels and fiber-glass.

Concrete reinforced with a wire mesh and known as ferro-cement has been used with very little supervision in some countries, and the needed materials are cheap and usually readily available. A strong case has

been made for every developing nation to invest in a

cement plant since the raw materials can be cheaply

furnished using local labor. The rest of the production

process similarly can make do with unskilled labor at most stages.

Brick and concrete block masonry:

crete block masonry are common.

Brick and conSteel: As a capital-intensive material, steel is rarer.

Its most common use is as a roofing material (in the form of corrugated sheets of galvanized steel or aluminum), and to a small extent as connectors for bolting and anchoring the various structural elements.

1

13
Plastics: Plastics are a highly adaptable material. Depending on the choice of components, they can be

tailor-made to adapt to most structural and enclosure needs of housing. Not enough is known about the weathering properties of plastics in outdoor use (as compared to traditional materials), especially in tro- pical areas such as those in this study. Use is most ad- vanced in the Philippines, which also is one of the

chief plastics producing countries in the Far East. They use native as well as imported raw materials

and processing machinery. Several important tests underway in Bangladesh are described later in this report.

Still, plastics are resisted as a new and unfamiliar

material. Solid-seeming and demonstrably durable

materials are preferred. Plastics are likely to be more

widely accepted in the future as they penetrate the

private, for-profit housing market and non-housing

uses such as clinics and schools. They can then be ob- served and their performance seen by those who presently must rely on housing provided by their governments or through their own labors.

Indigenous fibers: Indigenous fibers, such as palm

leaves, coconut husks and peanut shells have served

as filler materials in spaces between structural supports or between roof rafters; and grasses such as jute

and hemp can be used as reinforcement for concrete

or adobe masonry.

2.3 PRIORITIES

A constant dilemma among policy makers in developing countries is the tug-of-war between food

and building materials for use of precious foreign ex- change. In most cases food wins out, as in Bangladesh,

placing increased pressure on development of a domestic materials producing capacity.

Facing Page: Houses such as this are flimsy but could be made to better resist high winds if adequately braced and

securely anchored to the ground.

U
3. REVIEW BY COUNTRY

The preceding material describes housing in the

Philippines, Jamaica and Bangladesh in terms of

their socio-economic profile and physical housing

characteristics. In the material that follows, there will be separate, detailed descriptions of conditions in each of these three countries. In this sense, this section should be seen as an extension of the previous one.

3.1 THE PHILIPPINES

The Philippines have the highest frequency of tropical storms (wind greater than 18 m/s) in the world.

Average annual frequency is 20.

Filipinos have always depended on water (whether

fresh or salt) for food, transportation and for watering

their fields. This is still the pattern in rural areas. This

attachment to low land and water logged areas led to a unique type of dwelling, with a raised floor on stilts. Communal activities centered around the houses of the village elders, who also were religious and

judicial officials. This organization has today been for- malized into the barrio, which is the lowest political unit of government.

15
3.1.1 The Filipino Family and Their Housing

Needs

The family is the strongest unit of society. Kinship is often extended as far as the third or fourth cousins. Families with at least three generations living in a

single house are common. Extended families exist not. only in the country but also in cities. Their percentage

in low income areas around Manila reaches 55 per- cent (family size ranges from seven to 11 in these

cases, with at least 18 percent made up of nine members). In times of crises, family members are expected

to share board and shelter with less fortunate relatives, especially parents in old age and widowed rela- tives with children. The family acts as the economic

unit in rural and urban areas. Children are seen as economic assets. A large family is regarded as a means

to social security.

3.1.2 The Community

Ranking cities in the Philippines have between 10 and 45 percent of their populations in slums or in squatter areas; the national average is five to six percent. Filipino squatters are said not to be shiftless people, but well motivated and resourceful. A study made by Jaime Laya, Remedios Balbin and

Romulo Neri of the Agno-Leveriza squatters area of Manila (see reference 7, part H) paints a grim physical

picture. Eight hundred dwellings are crammed into two city blocks behind a prosperous seeming facade of

solid apartments and houses. Most structures are of one or two rooms, without running water or toilet. About 1 2 percent of surveyed heads of household were unemployed.

Yet the study team noted little active discontent;

rather, they found an attitude of initiative, of moving

on by one's own effort and enterprise. Education level was relatively high (7.1 years of schooling on average

for heads of household, more than needed for the jobs

they hold), and income level varied widely, from

destitute to families with a refrigerator, television set and telephone service. Another study, by Mary R. Holnsteiner (see reference

7, part I) confirmed a sense of excitement among

squatter families after they left a dull rural existence and moved towards economic opportunity in the city. One recommendation of this study, which looked

into options for relocating Manila squatters, was to weigh with care any plan for moving families off to a

site too remote from urban job opportunities.

3.1.3 The Need for Housing

The estimated annual need for urban housing alone averages 100,000 units—to accommodate population

increase, new family formations and replacement of squatter dwellings. The cost of land is high and this

has a direct effect on the high cost of adequate housing. In addition, wholesale and consumer product

prices rose sharply between 1970 and 1973. The

average increase for all commodities was 25 percent;

for most construction materials the figure was 40 to 60

percent. On the other hand, downward pressure on

the cost of materials for conventional construction is exerted by the low cost of delivering materials, since

production is spread throughout the country.

t m 1 \ 60%1

Prio-5 of CflnstKUctJon materials

Iwt n#*t Wicx CcS V*MCk OA>

<alL otter oototAodAxc^

3.1.4 Economic Aspects

The Filipino economy as measured by its Gross National Product (GNP) rose at an average annual rate of

6.6 percent during 1968 to 1973. Investment in housing rose from 2.8 percent of GNP in 1967 to 4.0 per- cent in the early 1970s. But to meet the country's total housing need of some 470,000 units per year, an

allocation of 5.7 percent is required. Average per

capita income ($130 in 1970, U.S. dollar equivalent)

also rose, and is expected to double in the next 10 to 15

years. Only 12 percent of the population (with annual

family income over $1490—U.S. dollar equivalent) can afford housing on the open market.(See reference

7, part A). Twenty-three percent can afford to own a house if offered long term cheap financing with modest land,

development and construction cost ($596 to $1489 an- nual income range). The rest cannot afford shelter at any cost. The amount a family can afford for housing varies

chiefly with its income and location along with other

lesser factors. For example, according to a study by

Sixto L. Roxas III (see reference 7, part E), a family

with an annual income of $300 can afford a house 1.3 times its income, or $390. At an annual income of $450, it can afford a house of 1.8 times its income, or

$805. This sets certain numerical limits on the cost of low income housing.

In addition, income varies in different regions of the country, with families in urban areas outside of Manila having a higher pattern of income than

Manila and rural areas (see reference 7, part E). All these economic aspects are important in determining

realistic parameters for the design and construction of low-cost, wind-resistant housing.

lb
3.1.5 Housing Characteristics

Key housing characteristics are shown in Table 2. Note the sharp differences between statistics for metropolitan Manila and for the Philippines as a

whole. Statistics are based on surveys by the Bureau of the Census and Statistics and by the Population Institute National Demographic Survey. They give little idea of the actual condition of dwellings themselves.

Table 2: KEY HOUSING CHARACTERISTICS IN THE PHILIPPINES3

a. TYPE OF DWELLING UNITS BY STRUCTURE (PERCENT)

Type Metro Manila Philippines

Single Family Dwelling 57.6 78.9 Duplex 5.5 4.1 Accessoria 15.1 2.3 Apartment 8.1 1.1 Barong-Barong (shack) 4.4 5.4 Commercial Building 1.0 1.3 Other or No Response 8.3 6.9

Total 100.0 100.0

b. NUMBER OF ROOMS IN HOUSEHOLD EXCLUDING BATHROOM AND TOILET (PERCENT)

Type Metro Manila Philippines

One Room 11.3 14.1 Two Rooms 22.5 28.4 Three Rooms 23.1 25.7 Four Rooms 19.8 14.3 Five Rooms 8.0 6.5 Six Rooms 3.8 2.6 Seven Rooms 1.3 0.8 Eight or More Rooms 1.6 0.6 No Response 8.7 7.0

Total 100.

1

4 100.0

c. DENSITY (PERSONS PER ROOM) WITHIN HOUSEHOLD (PERCENT)

Type Metro Manila Philippines

Less than one person

per room 5.1 6.1 1.0 to 1.9 persons per room 27.8 27.4

2.0 to 2.9 persons per room 26.5 27.4

3.0 to 3.9 persons per room 14.1 13.7 4.0 to 4.9 persons per room 7.7 7.7

5.0 to 5.9 persons per room 4.2 3.7 6.0 to 6.9 persons per room 1.5 2.8 7.0 to 7.9 persons per room 1.8 1.7 8 or more persons per room 2.7 4.5 No Response 8.7 7.0

Total 100.1 4 100.0

^See reference 13. 'Rounding error.

17
3.1.6 Population trends 3.2 JAMAICA

Table 3 shows the results for the Philippines of a world-wide survey conducted by the United Nations

to identify population trends. The information is up- dated through June 1974; population figures are broken down by urban and rural, and indicate projected rates of increase. Information for five-year

periods from 1975 to 2000 are given. The trend shows

increasing urbanization although the rate of increase

is shown to be decreasing.

l«7* 41000

3.2.1 Socio-Economic Aspects

Virtually all Jamaican housing built by the private

sector today falls outside the definition of low-income

housing. To qualify, the cost of house plus a developed

site must be under $5,500 (U.S.). Whereas 33 to 42 m: (350 to 450 ft 2

) is a minimum standard for social housing in developing countries, a more attainable stan- dard for people with no fixed income brings this closer to 19 m2 (200 ft 2

) in Jamaica. In such cases, provision is usually made for the owner to extend the house at some future date.

Traditionally, urban low-income housing has been

high-density apartments—terrace houses or small groups of houses closely clustered around a communal

yard.

Detached houses have been more typical of middle in- come groups, and have become the goal of upwardlymobile low-income groups. Over the past 10 to 15 years this has caused developers of low-cost housing,

in order to keep prices down, to erect groupings of closely spaced, single-story detached units on tiny

lots. Oddly enough, a middle-income trend back to apartment living is seen as encouraging a similar trend among low-income groups, which may now be more

likely to accept multi-story and terraced housing,

Table 3: POPULATION TRENDS IN THE PHILIPPINES, JAMAICA AND BANGLADESH

1975-2000s

Population (in thousands)

Urban Rural Total

Percent Urban

Annual Rate of Increase Preceding 5 years (Percent) Urban Rural Urban Rural Total Difference

a. PHILIPPINES

1975 15837 29468 45305 34.96 4.51 2.70 3.32 1.81 1980 19936 33594 53530 37.24 4.60 2.62 3.34 1.98 1990 31272 42132 73404 42.60 4.39 2.07 3.03 2.32 2000 46068 47956 94024 49.00 3.66 0.99 2.25 2.66

b. JAMAICA

1975 830 1199 2029 40.89 3.51 0.22 1.50 3.29 1980 973 1199 2172 44.79 3.19 -0.00 1.36 3.19 1990 1291 1173 2464 52.38 2.72 -0.27 1.24 2.99 2000 1619 1107 2726 59.39 2.06 -0.74 0.88 2.80

c. BANGLADESH

1975 5296 73616 78912 6.71 4.87 2.78 2.92 2.09 1980 6850 85243 92093 7.44 5.14 2.93 3.09 2.21 1990 11657 114235 125892 9.26 5.36 2.91 3.12 2.45 2000 19395 146117 165512 11.72 4.97 2.28 2.57 2.69

'Courtesy United Nations.

18
with its more efficient use of limited land and

resources. A useful if not totally representative picture emerges

from a survey of housing conditions in the Delacree Pen district of Kingston, Jamaica. Delacree Pen is the

site of an urban renewal project. The survey disclosed

that of the 4,935 households, 68 percent lived in one

room; 18 percent in two rooms and eight percent in three rooms. The most common household size was

from five to seven (24 percent); 37 percent were of one

or two persons, and 1 1 percent had eight or more

members.

A notable feature of the Delacree Park urban housing

project (located in the Delacree Pen District) is its character as a housing cooperative. Such a cooperative, established with government, World Bank or

other subsidies, is a useful vehicle for erecting housing, in the construction and maintenance of which the occupants have a strong social and economic stake.

Eventually 350 units will be built in Delacree, in the form of wind-resistant two story garden apartments

arranged in clusters of six. The program has been

well-received—both in its social and its economic

context. One difficulty has been adherence to occupancy stan- dards—a common problem in developing countries. Delacree Park units, which have a living room and

two bedrooms, may house up to six people, according

to government standards of two to a room. In practice, families sometimes have as many as seven

children; consequently the government, knowing it cannot afford to subsidize such supplemental spaces,

will permit its occupancy standard to be exceeded by

up to 50 percent.

By and large, cooperatives are now an accepted

method for erecting housing in Jamaica. The Jamaican

Ministry of Housing has created a Division of Cooperatives and Condominia to coordinate this

effort. o

Oc^p^c^ 5o%

3.2.2 Housing Characteristics (See Table 4)

Jamaicans generally prefer concrete houses and do

not like houses made of light-weight materials, unless they are forced to live in one for financial reasons (see reference 1). Almost half of Jamaican housing is made

of concrete. Until recently there has been a bias against precast concrete houses (especially those of thin cross-section) but this is disappearing.

Table 4: KEY HOUSING CHARACTERISTICS IN JAMAICA6

a. DISTRIBUTION OF DWELLINGS BY TYPE OF

TENURE (PERCENT)

Type of Tenure Total Urban Rural Owned 52.4 29.7 70.8 Leased 2.5 3.9 1.4 Rented 36.5 59.9 17.6 Rent-free 7.9 5.8 9.6 Squatter 0.4 0.5 0.3 Other 0.3 0.3 0.3

Total 100.0 100.1 7 100.0

b. DWELLINGS CLASSIFIED BY TYPE

Type of Dwelling Number Percent

(to nearest thousand)

Separate house 328,000 78.0 Flat/Apartment 67,000 16.0 Barracks 3,000 0.7 Out-Room 4,000 1.0 Part of Commercial Build- ing 12,000 2.8 Other Private 4,000 1.0 Other 2,000 0.5

Total Dwellings 420,000 100.0

c. PERCENTAGE DISTRIBUTION OF DWELLINGS BY NUMBER OF ROOMS

No. of Rooms Total Urban Rural

1 32.7 42.3 24.9

2 26.3 19.6 31.7

3 16.1 11.7 19.7 4 8.5 7.5 9.3

5 5.3 5.9 4.9 6 2.8 3.3 2.4 7 2.6 3.4 1.9 8 or more 5.8 6.3 5.3

Total ioo.r 100.0 ioo.r

''See reference 1. 'Sum total exceeds 100 percent due to rounding error. The most popular material among all income groups

is hollow concrete block masonry. Physically, low- cost housing in Jamaica falls into six types (see reference 1):

19
Wattle and daub:Until the 1930's rural owners built most low-cost houses in this fashion. The framework

of wooden posts and beams, with sticks interwoven

horizontally between the posts, was the wattle. This was daubed inside and out with mud from available

clay, to create solid walls. The roofs were pitched and

made of a thatch made from bundles of dried leaves and tied in place.

Timber stud and horizontal boarding:Roofs are

pitched, made of timber rafters covered with corru- gated iron sheets or wooden shingles.

Brick or concrete nog: Wood studs receive a brick or concrete infill or nogand are covered with a lime or cement plaster. Houses are usually raised two or three

feet above ground.

Hollow concrete masonry:Concrete blocks are manufactured locally: cavities are filled with concrete during construction, and steel bars are added to rein- force against wind and earthquake. Poured in-place

reinforced concrete stiffener columns should be in- cluded in panels over 4.9 m (16 ft) long, but are often omitted in low-cost housing. Reinforced concrete belt beams are used to cap walls at roof levels.

Large-panel precast-concrete systems:Single panels can extend to the full length and height of a unit. Wall

and roof panels are lifted by crane and connected by

welding at matching steel inserts. (These systems are not strictly speaking low-cost but could be if one steps

up volume of production and accepts a lower stan- dard of finishes).

Small-unit precast concrete systems:Precast concrete

posts arexombined with precast concrete or timber

beams, with an infill of concrete panels known as

boards. Remaining housing is constructed of brick or stone.

3.2.3 Housing Programs

Except for the 20 percent of needed units supplied or aided by the government there is presently no machinery for providing housing for the very bottom

of the income scale. The mechanism used with regard

to the poorest citizens is either the continuing growth

of shanty towns or the increased subdivision of exist- ing houses to accommodate new households.

In addition, the government now has underway a

sites and services project designed to bring housing,

essential community services and job opportunities to Jamaica's lower income groups. The project is fi- nanced jointly by the Government of Jamaica and the

20
International Bank for Reconstruction and Development (IBRD). A special unit has been created to carry

out the project, which should demonstrate a more

practical and desirable alternative to existing low-cost housing programs in Jamaica. This is so because the

project has been designed on the basis of what low-in- come households can afford. Together with training

and technical assistance, the project is expected to lead to institutional reforms that will provide the management for long-term housing programs.

Families with an annual income of less than $1,650

(1974 U.S. dollar equivalent) are eligible (see reference

1). The goal is to provide 6,000 serviced lots in the next three years. Lots are to be available in three options: with connections for electricity, water-supply

and sewerage, plus materials for a toilet-kitchen- shower core unit; the same, but with a built core unit,

plus materials for shelter and enclosure for the rest of the house; and the same as the preceding, but with the

core-unit and shelter built, and materials only pro- vided for enclosure of the rest of the house. Serviced

lots are to be occupied on a leasehold basis, and loans

for materials will be provided through credit unions.

The project will also provide related utilities, known

as infrastructure, and community facilities: primary

school, day-care centers/basic schools, health centers, community centers, trade schools, police posts and

market sheds. Industrial financing for small to medium-scale industries (e.g., garments, leather goods, ceramics, toys) will create additional employment at a low-cost per job ratio; the required supporting consulting services will be provided.

Although the main focus of the Jamaican government

is on sites and services, there are other government

programs. These consist of a mix of government-built

housing for sale or lease (1970-1975 goal; 3,125 units); owner-occupied government subsidized units (3,600

units); rural housing projects (4,880 units); indigent

housing built on land owned by recipient (2,250 units); urban renewal projects focused on Kingston (4,876

units); plus assistance furnished to housing cooperatives (see reference 1).

3.2.4 Wind Patterns

Records made between 1886 and 1967 show that the paths of 19 hurricanes and tropical storms passed

directly over Jamaica and those of 98 (48 of them having hurricane force winds) passed within 240 km (150

miles) of the island (see reference 1).

Despite the frequency of hurricanes in the Caribbean,

direct hits on Jamaica are clearly few when compared

with the number of near misses. Near misses are often accompanied by flood rains which cause much

damage.

3.2.5 Population Trends

Table 3 shows the results for Jamaica of a world-wide survey conducted by the United Nations

to identify population trends. The information is up- dated through June 1974. Population figures are broken down by urban and rural, and indicate projected rates of increase. Figures for periods from 1975

to 2000 are given. The trend shows increased ur- banization along with a net decline of population in rural areas.

1^

^^_ jj>uaL-.

117*

3.3 BANGLADESH

3.3.1 Socio-Economic Aspects

Bangladesh is a nation with one of the highest population densities and fastest growing populations in the world (see table 3). The country is faced with various

problems:

• Steady population growth has forced families

to live on land that is increasingly substandard and

subject to wind-induced flooding. • Periodic flooding of low-lying land further in- creases density—from about 525 persons per km2 (1360 per mi2

) to a temporary 15,400 persons per km2

(40,000 per mi2

) in coastal storm regions, as families

flee to land left dry.

• The partition of India and East Pakistan (now

Bangladesh) in 1947 left the higher land, with its sup- ply of solid construction materials such as stone and

^imber, on the Indian side of the boundary, while the Bangali population on the treeless alluvial plain was

left with few resources for protection. • The industrial output accounts for only nine

percent of the gross domestic product (mostly jute

processing) (see reference 5). • The average number of rooms in 1960 per household was 1.8. Fifty-three precent of householders lived in single room dwellings, and the

23
average density of occupancy was 3.2 persons per room. In the case of 31 percent of the population, five persons or more share a room. Clearly, any damage

from intense windstorms risks major casualties to a population as densely crowded as this.

Ninety-two percent of the population is rural. The

rural population lives in the patriarchal family compound. When sons marry, a new room is erected for the new household on the same field as the parents, next to the parents' house. Thus, houses occupied by

families that are paternally related are grouped

together. These clusters provide shelter to families numbering as many as 40 members; even higher

figures are common. Houses are usually surrounded

by dense trees and other tropical vegetation.

Rural housing as part of the agricultural

system:Bangali villagers view housing as part of their agricultural system, rather than as a building dis- cipline as in the West. Thus, house building and repair

is seasonal, like other farm activities. It helps relieve unemployment. Villagers will grow building

materials for houses on their own land. A tree, for ex- ample, will serve as a fruitbearer, windbreaker and

fuel, until needed as a building material.

Similarly, a man's jute and the earth itself serve him

both for agriculture and for building.

Due to the climate, the bamboo kutcha house

(described later) itself decays over a 10-year cycle, if not destroyed by a storm before then.

Responses to disaster: A report prepared after the

disastrous November 1970 cyclone reveals an interest- ing set of attitudes. Fifty-seven families of various

economic levels in the community of Galachipa were

surveyed. Dr. Aminul Islam who collected information after the May 1965 and November 1970 storms,

found that:

• After 1965 no family wanted to move, though

many families rebuilt their houses using higher

plinths and stronger posts • After 1970 only five families wanted to move;

56 still lived on the site of their old home

• Thirty-eight families were still living more

than 1.5 km (0.9 mi) from a pucca (well-built) structure

that could shelter them in a storm

• Fourteen were still living 5 km (3 mi) from

a pucca structure • Nineteen families still needed a boat to reach a pucca structure • Not even half the families would spend their money first on housing. The others' priorities were

food and cattle. The majority said that if they had the money for housing, they would build one small pucca house,

rather than several kutchas (or low quality houses) or corrugated iron (CI) houses. In general terms, the survey found the families fatalistic and pessimistic over protection measures.

3.3.2 Housing Patterns

The rural population is divided into land owners and

landless laborers. One out of five villagers is landless. The average land owning villager has 0.6 ha (1.5 acres) and usually rents another acre from well-to-do

villagers. Houses tend to be scattered throughout the

village.

22
Rural houses are known as"kutcha" or raw structures, with a plinth made of mud, and walls and roofs of bamboo, straw and leaves. These houses need to be

maintained constantly and seldom provide safe shelter against rain and wind. Ninety percent of rural houses are built this way. Only about one in a hundred has walls of concrete, baked brick or stone. About one house in three has roofing made of corru- gated galvanized iron or asbestos cement. As 72 percent of the urban population cannot afford to pay rent for even the cheapest housing, they live largely in flimsy shacks, mostly in squatter settle- ments. This housing is made of bamboo, often consist- ing of a piece of woven split bamboo fencing bent in the shape of a semi-circle. Headroom is low and occu- pants spend most of their time outdoors. Even moderate winds blow these houses away despite efforts to hold them down by putting counterweights on roofs.

Typist rural keu^e

prth, fen**** oa*.cL 'ctfrrw^aGfc-oL iron roofEh

_1L

The stronger urban houses usually have burnt clay brick walls, with flat reinforced concrete roofs. Since

the walls are usually 0.25 m (10 in) thick, gravity tends to preclude failure through wind stresses. Failures are due largely to substandard mortar or poor workmanship.

What happens to the houses:In the 1970 storm, it was

the wind that caused initial housing destruction; the storm surge accounted for people and animal

casualties. Here is how the materials fared:

Material Condition

Thatch

Bamboo matting

Wood or bamboo

supports

CI sheets

0.13 m (5 in) brick

Destroyed or lost Usually destroyed or lost

Broken, recovered, reusable Damaged, in part reusable Destroyed. If preserved hard

to reuse

0.25 m (10 in) brick Intact if concrete roof

Middle and upper income rural families use CI sheet and wood. These resist wind and water if well-built.

If not, owners can retrieve materials and rebuild unless the materials are scattered by flood waters. However, partial losses after a storm often cost more

to make up than would a total rebuilding of the less permanent kutcha house.

Other types of housing and housing materials: CARE, Inc. type buildings (named after the U.S. relief organization) use soil cement blocks and corrugated

iron sheets for roofs. Blocks roughly the size of a U.S. concrete block are made in a simple-to-use machine

which compreses a mixture of about 90 percent nonsaline soil and 10 percent cement to make about 300

LuSe Wick wallf?

r nil

H

faUui (if U\C o^tt io%

AfV ^M,ck^rtC to WvM^

k/vfc tf«e~ mi??

23
blocks a day. A typical house requires approximately

1200 blocks. A minimum of skilled labor is needed to construct this kind of house, which is very popular in the country. The key to roof wind safety is to properly anchor the roof to the block walls. CARE, Inc. has also developed a new composite build- ing material, made of pulp from the core of the jute

plant, jute cloth and a plastic resin for binder and fac- ing. This seeks to combine a locally plentiful material

(jute) with synthetic binders which can be manufactured into panels by domestic industry.

Several variations of material and configuration have

been formulated for laboratory testing, prototype construction and wind testing of full-scale units. Four

prototypes have been developed so far. These are:

• A pie-shaped, domed structure made of a 19 mm (3/4 in) compressed jute-waste board faced with

polyester resin and glass. Public reaction was good

until the facing was identified as plastic, for plastic was identified in the public mind with a brand of cheap and brittle crockery. Those who acknowledged

the strength of the plastic nevertheless faulted the house for its roundish dome-like shape. This made

partitioning difficult and made it unsuitable for lowincome families—especially the 80 percent Muslim

families with their tradition of isolating women in one part of the house.

• A self-supporting house, rectangular in plan

and with an elliptical roof profile, with curved panels

made of the same combination of synthetic resin and

jute. No component was to weigh more than 45.4 kg

(100 lbs), so it could be easily managed by two men. It was designed to resemble traditional house shapes.

• A structure using the above materials but geared for use in larger, non-residential buildings.

• A structure designed to substitute the

jute/plastic material for the traditional thatch or cor- rugated metal roof and its customary wood or bamboo

support rafters. The new roof of this prototype was

designed to fit over either traditional or new walls.

db fee uzaL uritk \^rA. o£

These four prototypes can be anchored directly to the

soil or to standard perimeter footing foundations.

Many of these prototypes have been used for other than residential purposes, and as such have been very

24
popular. These uses have included a medical operating theater, dispensary and office. From a socio- economic view, this is seen as a useful lesson, in that

citizens of Bangladesh can get to know the structures

in a service role without having to accept them sud- denly into their personal lives as homes.

Two additional CARE, Inc. prototypes of more tradi- tional appearance were developed in the United

States using a panel made of a jute reinforced

polyester core and a fiber-glass reinforced polyester

facing. The three by six m (10 ft by 20 ft) two room

units successfully passed severe simulated wind and

water tests.

Reinforced concrete shell roofs of hyperbolic

paraboloid shape have been used for industrial and

suburban housing. The roof is anchored to the sup- porting brick walls by means of 13 mm (1/2 in) mild

steel bars at the corners.

\h anchored

to t>tickba$e.

One related project funded by AID's Office of Science

and Technology in Bangladesh contains several in- novative ideas and offers a number of lessons in socio- economic planning (see reference 4). The project was

carried out by a Carnegie Mellon University team

headed by Charles H. Goodspeed and Volker H.

Hartkopf. During 1974 and 1975 the team—which in- cluded architects, engineers, planners and

sociologists—developed a prototype, very low-cost

(goal: $10 per person per shelter) housing unit for use

in a variety of relief and rural development situations

in Bangladesh.

The prototype had to be locally acceptable, and subject

both to easy upgrading or to a reduction back to its basic materials. The result was an A-frame modular housing system

which was able to use a wide variety of local, indigenous materials. The structure was cheap, labor in- tensive, easily erected and reportedly resists wind

and floods. The advantage from a wind resistance standpoint is the inherent strength and stability of the

/4-frame. The structure, with its thatch roof and an in- genious venting detail, appeared to offer some

pressure equalization to reduce the effects of high

winds exerting strong interior upward pressures on

the roof. It was not evident from the project's report

how the bamboo framing members were to be

anchored in the soil to prevent overturning of the

structure in high winds.

From the viewpoint of cultural acceptance, Dr. Vijai

Singh, a sociologist on the team, reported a good deal

of opposition to the test unit, both among the Bangalis

and Biharis. The shape was not common in the area (some residents commented that they looked like "Christian churches", though these feelings might

have been influenced by their understanding that these projects are financed by Westerners, and it was

"too tall." Residents said that continuous reduction of space from ground to roof due to the A-frame was rare in traditional Bangali architecture. The

popular rural housing structures have four walls on

the ground despite variations in roofing patterns. Most of the brick houses have flat roofs and others are

raised in the middle. Dr. Singh felt the structures could be made more acceptable by lowering their height and changing them in appearance to conform

to the traditional structures.

All the respondents complained about the tightness of space inside the structures and felt they had been built without due concern for the needs of the families liv- ing in them. Most complaints centered on lack of storage and kitchen space. Also, residents in some

areas felt the windows were too high, and should be lowered so some air could flow at floor level. It was

difficult to sleep inside in hot and humid weather.

Several different door styles were tried, but none

proved popular and all residents suggest a bigger entrance and a door that could be shut and locked.

The original structures appear to be a version that will withstand high wind, but they have yet to be formally

tested in a high wind situation, so that their perfor- mance under such conditions is still largely unknown.

3.3.3 Housing Programs

The 1971 war of independence left about two million

families homeless. Sizeable housing rehabilitation and

reconstruction efforts are now under way in rural areas. The Delta Housing Program:Beginning in 1972, a rural cooperative housing scheme got under way in the Delta area, a coastal strip of 10,400 km2 (4000 mi :

) with 4,270,000 inhabitants. The program's main features

25
have been: • Erection of 7500 - 3 by 6m (10 by 20 ft) soil-ce- ment-block houses on burnt-brick foundations to withstand severe flooding and substantial cyclonic

winds. • A cooperative plan under which farmers and

fishermen undertake to repay 50 percent of the cost of the house out of agricultural income to their local cooperative society. These societies are linked into a complex cooperative system known as the Integrated

Rural Development Program. (The other 50 percent of

cost is subsidized). • To reduce the villager's concern about the annual fate of his house, and thus show the villager how

to attend more to long range agricultural planning

and development; and, further, to reduce the

villager's (and the government's) repair expenditures

after every cyclone season.

Siting: Creation of either artificial barriers or embankments in low-lying areas (so as to either shield houses or raise them above mean high flood levels) has been proposed as part of any new wind and flood protection program.

It was found, for example, that Dutch polder type barriers have protected many houses in recent storms. Even when the water breached the barriers and

caused flooding, it did not destroy the houses. By and large, raised embankments or platforms are thought a better approach. Its main features are: • Construction of a platform 2.4 m (8 ft) above mean high tide level. Over it, erect a small 5.5 m2 (60

ft 2

) pucca quality shelter house of 0.25 m (10 in) brick

with a flat roof (behind a parapet) 4 m (13 ft) above

this platform includes a 0.9 m (3 ft) plinth A man, woman or child standing on such a roof platform

would be at least 7.3 m (24 ft) above mean high tide

level; this is said to be protection against even the worst onslaught of a storm surge.

(0.25*0

brick.

• Assignment of responsibility to each bari or community for building and maintaining such a shelter, the interior of which could serve as storage. Nucleus housing: Widening the concept of nucleus housing has been proposed. Under this concept, a

basic, small wind-secure house (such as the soil-ce- ment CARE, Inc. house) serves as a starting point for adding space horizontally or vertically to the taste of the owner or tenant. Open, bamboo-and-thatch leanto additions have been created in some localities. In others, soil-cement blocks have been plastered to better resist wind, floods and temperature extremes. Occasionally, a second and even a third story are added.

WusJL ztUMtr Iwrn&eMaterials: Since villagers are inclined by their socio-economic priorities to put food and cattle ownership before housing, a plan is proposed to ensure building materials delivery. Its main features are: • Government subsidies should be in the form of materials not funds. • The goverment should set up local technical

assistance units which would help with organized

harvesting of wood; introduce mechanized milling to ensure tighter fit; show how to cultivate plants that are sources of building materials (such as the Nipa

palm which is semi-aquatic and does not displace

food growing and grazing land); and provide seedlings.

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p lace fo-etC ^nvj^Jj tk*A

26
• Clay is plentiful in Bangladesh, and there is a 1000-year old tradition of burnt brick construction. Crushed, these bricks can replace the imported ce- ment in concrete. It is useful as a foundation and, in enough thickness, 0.25 m (10 in) to better resists ex- treme winds. • The making and use of cement-soil block. (This

topic has been discussed elsewhere in this report.)

3.3.4 Wind and Flood Patterns

The most common sources of wind in Bangladesh are the cyclonic typhoons, tornadoes and norwesters. Damage is not only from wind pressures but from

high walls of water known as storm surges. Thus, the cyclone of November 12, 1970 caused storm surges some 7.6 m (25 ft) high; nearly 100 percent of the kutchas and semi-permanent houses were

demolished in the area of the storm. The coastal areas

of the country are the most vulnerable to cyclonic

storms. Tornadoes are the most destructive storms. They

usually happen on land during the warm season in

flat areas, with few natural barriers to hinder them.

Eighty-nine m/s (200 mph) winds are common, but maximum wind speeds up to 223 m/s (500 mph) have

been estimated by some experts.

Storm surge: The storm surge that accompanies

cyclones in coastal Bangladesh usually moves inland

at about storm speed 2.2 to 1 1 m/s (5 to 25 mph). Its mean depth over a particular site is determined by

five variables, the last two of which can to some extent be influenced by man.

1. Severity of storm (this determines height of water over normal sea level).

2. Level of daily sea tide at time storm strikes.

3. Land configuration and wind direction (these reinforce or impede rise of water).

4. Elevation of site (natural plus build-up).

5. Distance from sea or major inlet (land, trees and

other vegetation resist flow).

27
Storm warning systems: The huge death rate of the November 1970 cyclone was due in part to the use of a new warning system unfamiliar to the coastal

villagers. Since then, the new danger—great danger

warning scale has been supplemented with a pre- paredness system under which 10 volunteers per bari , each equipped with signals, lights, etc., are linked by

radio to Red Cross central headquarters in Dacca,

which receives and disseminates the latest storm in- formation. There are also specially trained local relief teams.

3.3.5 Population Trends

Table 3 shows the results for Bangladesh of a worldwide survey conducted by the United Nations in an

effort to identify shifting population patterns. The in- formation is updated through June 1974. Population

figures are broken down by urban and rural, and indi- cate rates of increase. Figures for periods from 1975 to 2000 are given. Population will more than double in a single generation, with the rate of increase of urban

areas expected to be over double that of rural areas.

1000

Facing Page: Sites-and-services concept may provide land, core walls and basic utilities. Families add rooms accord- ing to their means.

28
4.0 CONCLUSIONS

A clearcut picture of problems, needs and solutions emerges from the diverse research reports, surveys and statistics that served as a basis for this report:

• As to the socio-economic aspects of designing

wind-resistant low-rise/low-cost housing, the cultural characteristics and financial capacity of low-income

groups must be taken into account along with the

technical criteria if sound solutions are to stand the

test of widespread acceptance. This does not mean

that new, stronger and less costly materials and construction techniques must blindly imitate traditional forms and processes. Nor, on the other hand, should

these ignore the long traditions of indigenous building

in the three countries discussed in this report. • One emerging result of new low-cost housing

tests in Bangladesh bears watching. The interim use of new prototypes for other than residential use, in a highly visible way as clinics and community offices, points up a viable way of exposing new forms and

materials to prospective users before they must take

the big cultural step and live in them as families.

29
viable ^se a£>

• Similarly, the so-called sites and services ap- proach, if tailored closely to the characteristics and

outlooks of the communities involved, can capitalize on the proven initiative, ingenuity and hardiness of squatter and similar families. This will help overcome

the chronic barriers of insufficient financial and

material resources in developing countries. • Closely allied with the thinking behind site and services is the wisdom of gearing innovations in materials or method to the relatively plentiful labor supply in most developing countries.

• Emphasis on use of local labor does not preclude prefabrication, but places new focus on the need to identify, produce, adapt or combine cheap

local substances made from natural earth, trees and

plants. Bamboo, various kinds of soil, as well as jute, hemp, cane, split trees, straw, peanut shells and

coconut husks are among materials that have been

combined with manufactured substances such as ce- ment, plastics and metals to produce inexpensive,

sturdy building materials. • How the building blocks are assembled is one

of the major touchstones for stable, wind and water damage resistant houses. The chief caveats are ade- quate anchorage of roofing materials and trusses (if any) to walls. Structural design of roof members,

splices and joints must accommodate high wind

velocities. Anchorage of houses to the ground must be

designed to prevent over-turning; and wall openings must be placed to avoid weakening the structure at vital points and to prevent wind from entering and

exerting interior upward pressure on the roof. Similarly, design features such as roof pitch and over- hangs must observe latest findings on positive and

negative wind pressure distribution. • Proper placement of houses in groups as well

as to accommodate prevailing wind direction and

land features will always raise the wind damage

resistance of houses. This should be one of the first cri- teria to observe when planning houses in areas subject

to extreme wind.

30
APPENDIX REFERENCES

(1) Adams, A. D., "Low-Cost Housing and Extreme

Wind-Related Problems in Jamaica," (Published

as part of U.S. National Bureau of Standards In- teragency Report NBSIR 74-567), (Washington,

D.C.: National Bureau of Standards, 1973). Available from NTIS, COM 74-11631.

(2) Bueneman, E., Special Report on Techniques of Aided Self-Help HousingCWash'mgton, D.C.: U.S. Department of Housing and Urban Development, 1973).

(3) Dybbroe, O., Building Research in Jamaica

(Kingston: Building Research Unit, 1966).

(4) Feasibility Test of an Approach and Prototype of Ultra Lou>-Cosf Ho«smg(Pittsburgh: Carnegie

Mellon University, November 1975).

(5) Choudhury, J. R., "First Report on Low-Rise,

Low-Cost Housing and Extreme Wind-Related

Problems in Bangladesh," FY74 Progress Report, NBSIR 74-567 (Washington, D.C.: National Bureau of Standards, 1973). Available from

NTIS, COM 74-11631.

(6) Dietz, A. G. H., and Poerbo, H., "Industrialized Housing in Indonesia," Industrialization Forum

vol. 6, no. 2(1975).

(7) Housing in the Philippines (Preparatory materials

for the Conference on Housing), (Manila: National Economic and Development Authority,

1973).

(8) "Housing Through Cooperatives and Other

Non-Profit Associations," Human Settlements (New York: United Nations, January 1974).

(9) "7500 Housing Units Near Completion in Rural Bangladesh," ICHDA Profile (Newsletter of the

International Cooperative Housing Development Association), (Washington, D.C.: Housing

Development Association, December 1974).

(10) "Human Settlements," Architectural Record,

(May 1976).

(11) Improvements of Slums and Uncontrolled Settle- ments (Report of Interregional Seminar,

Medellin, Columbia, February 15 -March 1 1970), (New York: United Nations, 1970). Sales No. E71.IV.6.

(12) Koenigsberger, O., Mahoney, C, and Evans, M., "Design of Low-Cost Housing and Community

Facilities," Vol. 1: Climate and House Design (New

York: United Nations, 1971).

37

(13) Manahan, G.V., and Ramos, J.M., "SocioEconomicand Architectural Considerations in Housing," BSS 56, (Report prepared for International Workshop on Development of Design

Criteria and Methodology for Low-Rise, LowCost Buildings to Better Resist Extreme Winds,

held in Manila November 14-17, 1973), (Washington, D.C.: National Bureau of Stan- dards, 1974). Available from the U.S. Government Printing Office.

(14) Rehabilitation of Transitional Urban Settlements (New York: United Nations, August 1971). Available from the Secretary General,

E/C.6/115.

(15) Reps, W. F., and Simiu, E., editors, Design, Siting

and Construction of Low-Cost Housing and Community Buildings to Better Withstand Earthquakes

and Windstorms, BSS 48 (Washington, D.C.: National Bureau of Standards, 1974). Available

from the U.S. Government Printing Office,

C13.29/2:48.

(16) Research Study of the Socio-Economic Aspects of Low-Cost Housing in the Philippines {Maka\.'\, Rizal: Sycip, Gorres, Velayo and Co., 1972).

(17) Rosser, K. C, "Housing for the Lowest Income

Groups: the Calcutta Experience," Ekistics Magazine (February 1971).

(18) Self-Help Practices in Housing: Selected Case

Studies, No. E73.IV.15. (New York: United Nations, n.d.). (19) "Sites and Services Programs: the Experience

and the Potential," Human Settlements (New

York: United Nations, October 1972).

(20) Dunham, D.C., Cyclone and Storm Surge Destruction (Dacca: United States Agency for International Development, June 1965).

(21) Sommer and Mosley, Survey of 1971 Cyclone - Affected Region of Bangladesh (Dacca: United

States Agency for International Development,

1971).

(22) Houses Can Resist Hurricanes (Madison: U.S. Forest Service, 1965).

(23) "Urban Area Problems: Housing, Slums and Uncontrolled Settlements, Recreation and Tourism," Human Settlements (January 1972).

Note: Documents identified in the list of references by NTIS may be ordered from National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, Va. 22161. Likewise, documents noted by

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