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close this bookJournal of the Network of African Countries on Local Building Materials and Technologies - Volume 3, Number 3 (HABITAT, 1995, 42 p.)
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View the documentThe Aim of the Network and Its Journal
View the documentForeword
View the documentImportance of Appropriate Building Codes and Regulations in Improving Low-Income Settlements Conditions in African Region*
View the documentKenya: Building Standards and Planning Regulations - The Kenyan Experience**
View the documentTanzania: Sustainability of Building Materials Supply in Dar es Salaam***
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View the documentPublications Review
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Tanzania: Sustainability of Building Materials Supply in Dar es Salaam***

*** By J. Mamiro, National Construction Council, Dar es Salaam

The National Construction Council is a Parastatal organization with the mission of promoting the development of the construction industry in the United Republic of Tanzania. Among the functions of the Council is to promote the use of locally-produced construction materials.

INTRODUCTION

Building materials play an important role in the provision of shelter. It is estimated that building materials account for more than 60 per cent of the total building cost, therefore, the provision of affordable building materials specially for the rapidly growing urban population cannot be overemphasized. The supply of industrial building materials like cement, iron sheets, etc., does not meet the demand any more and the need to develop and use other locally-available materials is increasingly being felt countrywide.

In the United Republic of Tanzania, use of alternative materials like stabilized soils blocks, lime, bamboo, etc., is still very limited. In an effort to promote the use of locally-produced materials, the National Construction Council has developed a database on the production and use of building materials, costs and research activities and findings associated with building materials. Although information on the production technologies for alternative materials is available, more effort is needed to disseminate it and make the materials acceptable to the target groups.

This paper looks at the present levels of supply of materials in Dar es Salaam, the sustainability of the supplies and options for alternative materials.

BUILDING MATERIALS

Dar es Salaam is the largest city in Tanzania with an estimated population of 2,000,000 people. The city which is also the main commercial centre has been growing rapidly in terms of population. The growth rate is estimated at 4.8 per cent per year. The rapid urbanization which is a typical characteristic of most of the towns in Tanzania has an adverse effect on the availability of essential services including housing.

Furthermore, the increase in cost of living makes housing and other related services unaffordable to the low and middle-income population. Another negative impact emanating from urbanization is environmental degradation due to overcrowding and lack of infrastructural facilities.

The major building materials available in Dar es Salaam include - stones, aggregate, sand, timber, soils, cement, lime, corrugated-iron sheets, roofing tiles, and thatch for roofing. Despite the long list of materials available, the commonly used materials are sand cement blocks for walling, cement for binding and iron sheets for roofing.

As it can be seen from the above table, the cost of cement - which is the most crucial and basic building material - has increased by 43 per cent between 1993 and 1994. Hence, inability of low-income population to build their houses using such an important material. The situation of low-income people is more desperate due to the fact that they cannot even afford to use lime. The cost of lime has increased five - fold between 1993 and 1994.

Table 1. Price of selected materials in Dar es Salaam

Material

Unit

Price (TSHS)

June 93

Sept. 93

Dec. 93

March 94

June 94

Sept. 94

Aggregate

m3

6500

8000

7065

7065

7065

7065

Sand

m3

1800

2400

3000

3000

3000

3300

Timber (soft)

m3

87000

92000

92000

102900

102900

102900

Cement

50 kg


1850

2350

2350

2350

2650

Ironsheet

m

1098

1230

855

1170

1230

1500

Lime

25 kg

555

555

1500

1500

1600

2500


Manufacture of hallow blocks (Sand Cement) - Mtambo Blocks Company, Dar es Salaam

STONES AND AGGREGATE

The type of stone found in Dar es Salaam is mainly limestone. There are reserves in Kunduchi, Boko, Bunju, Mjimwema and Mbwamaji. Mining is done by both licensed and unlicensed (informal) miners.

There are 60 licensed miners operating in Dar es Salaam. The total production of aggregate and stone from the licensed mines is as follows:

Table 2. Stone and aggregate production in Dar es Salaam (licensed producers)

YEAR

AMOUNT (TONS)

1990

520,000

1991

600,000

1992

700,000

1993

750,000

Source: Zonal Mines Office, Dar es Salaam

In addition to licensed miners there are a number of unlicensed miners estimated at between 1000 to 1500. These are hand-diggers operating mostly from old mines and other restricted areas. The cost of aggregate produced by hand is half of that produced by crushers.

However, the quality is not guaranteed with respect to size and hardness. Most of the stones used for hand crushing are soft and as a result a lot of dust is included in the aggregate. The estimated production of this group is as follows.

Table 3. Stone and aggregate production by unlicensed miners

YEAR

AMOUNT (TONS)

1990

42,000

1991

45,000

1992

65,000

1993

84,000

Source: Zonal Mines Office, Dar es Salaam

Stones are used mainly in floor construction as hard core. Apart from the use of stone for cladding walls, there is very little use of stone in masonry. Although there are no records available on the size of stone and sand reserves, there are indications that these reserves will not last for long.

The city of Dar es Salaam is expanding rapidly and most of the mines which used to be far away from residential areas are now surrounded by houses. In Kunduchi area where most of the stone and aggregate is mined, it is no longer allowed to blast using dynamite because of the proximity of the mines to sensitive buildings and services. This makes the supply of this material very expensive because digging has to be done using mechanical means.

SAND

Sand is another major building material used in Dar es Salaam. There are two sources of sand in Dar es Salaam. River sand which is recovered from rivers and quarry sand. The major sand deposits are located in - Mpiji River, Chamazi, Mbande, Tuangoma, Kitunda, Kipunguni, Majohi, and Pugu Mwakanga.

Like stones and aggregates, sand is also mined by both licensed and unlicensed miners. There are 20 licensed sand miners in Dar es Salaam. The total production from these mines is as follows:

Table 4. Production of sand from licensed mines

YEAR

AMOUNT (TONS)

1990

1,512,000

1991

1,764,000

1992

2,016,000

1993

2,268,000

Source: Zonal Mines Office, Dar es Salaam

The number of unlicensed miners is estimated at 200. The total production by the unlicensed miners is as follows:

Table 5. Production of sand by unlicensed miners

YEAR

AMOUNT (TONS)

1990

252,000

1991

258,000

1992

504,000

1993

663,000

Source: Zonal Mines Office, Dar es Salaam

Sand is used mainly in the production of sand cement blocks. Production of these blocks is done by both large-scale producers, small-scale producers, and individual developers on construction sites. The quality of these blocks vary depending on the producer. The sand cement blocks are used mainly by the middle and high-income groups.

TIMBER

Poles are supplied mainly from natural forests in neighbouring regions while sawn timber is supplied mainly from plantations in Iringa, Mbeya, Mtwara and other regions.

Timber is used mainly in pole and mud construction. It is estimated that 45 per cent of houses in urban centres are constructed with pole and mud. These houses are found mainly in the unplanned outskirts of the city. The life span of these houses is estimated at 5 to 7 years. This makes it very uneconomical. There is a need to improve the technology of pole and mud construction.


Small scale production of Sand Cement blocks - Mtambo Blocks Company, Dar es Salaam

The supply of timber to Dar es Salaam for the past five years is shown in 6 table below.

Table 6. Timber supply for Dar es Salaam

YEAR

POLES NO

SOFT WOOD

HARD WOOD



Treated

Untreated

Logs m3

Sawn timber m3



Sawn timber m3

Sawn timber m3



1993/94

102356

1129

55,319

157,62

24,192

1992/93

129452

879

43,050

46,280

18,827

1991/92

244388

1954

95,746

61,600

41,872

1990/91

93924

1560

76,482

35,984

33,446

1989/90

201340

1720

84,318

73,772

36,874

Source: City Natural Resources Office, Dar es Salaam

The figure for poles represent poles supplied through licensed dealers only. This figure can be much higher if individual suppliers are included.

SOIL

Soil is a building material which is yet to be fully utilized in Dar es Salaam. Apart from being used in raw form to fill in mud and pole houses, soil finds very little use in housing. Due to the ever increasing prices of the industrial building materials and the decreasing supply of cement this trend has to change.

Good quality clay is available at Kisarawe in Dar es Salaam. The only clay brick and tile factory situated in Kisarawe has topped production. As a result there are no burnt bricks or clay tiles in Dar es Salaam. Soil stabilization using cement, lime, pozzolana, etc., could also be employed in production of blocks.

CEMENT

Most of the cement used in Dar es Salaam is supplied from the Wazo Hill Factory. Cement is the major binder used in housing construction in Dar es Salaam. However, the price of cement is high and not affordable to the low income population. The supply of cement has also been dropping due to production problems. For the past 4 years the supply of cement to Dar es Salaam has been as follows.


Small scale production of concrete roofing tiles - locally fabricated production machine. Femara Company, Dar es Salaam

Table 7. Supply of cement to Dar es Salaam

YEAR

AMOUNT (TONS)

1990

240,615

1991

269,799

1992

262,624

1993

225,303

Source: Saruji Corporation, Dar es Salaam

As can be seen, there is a decrease in the supply of cement and the situation will probably remain unchanged for the years to come.

LIME

Lime is produced at a very small-scale in Dar es Salaam. Although the raw material for lime is abundant, the use of lime in construction is not popular. Surprisingly, the price of lime is higher than the price of cement. This is mainly due to inefficient production methods. Lime could be used to supplement cement in most of the housing construction being carried out in Dar es Salaam if improved production technologies could be employed to reduce its cost.

ROOFING MATERIALS

The supply of factory made roofing materials in Dar es Salaam is adequate and it seems that supply and demand balance each other. The high prices of these materials may be a contributing factor. The most common factory made roofing material in Dar es Salaam is iron sheets. These are produced by the Aluminium Africa Company. The prices of these corrugated iron sheets has been going up and the sheets are now becoming unaffordable to the low-income segment of population.

Another roofing material in use is concrete tiles. There are three tile factories in Dar es Salaam. These type of tiles are mostly used by the high-income group.

The use of fibre reinforced roofing sheets and tiles is not yet very popular although there are a number of small-scale producers. However, for the low-income population the thatch is still the main roofing material.

ENVIRONMENTAL PROBLEMS

The supply of building materials in Dar es Salaam is associated with adverse environmental problems. The extraction of aggregate especially by the unlicensed miners is damaging the environment. Moreover, the mines which are extended to restricted areas such as roads, power lines, and water pipes pose a danger to these lifelines.

Similarly, extraction of sand is contributing greatly to environmental degradation. Surveys made recently show extensive mining of sand in unauthorized areas. The effect of the illegal mining is the destruction of river beds thus prohibiting the flow of sand to the ocean which is causing beach erosion currently taking place. Illegal miners also extract sand from pits in residential and commercial areas, a practice which leaves big unplanned pits in the areas, thus, posing a danger to already existing buildings and infrastructure.

CONCLUSION

The sustainability of building materials supply to urban centres will depend very much on the production and use of alternative materials. Considerable research has been carried out in this sector, however, what remains to be done is the dissemination of information to the end users. Furthermore, over dependency on industrial materials such as cement, corrugated-iron sheets etc., should be avoided so as to increase the use of locally-produced materials.

Environmental impact assessment should also be taken into consideration seriously when deciding on materials to be promoted.

REFERENCES

1. United Nations Centre for Human Settlements (Habitat), Global Strategy for Shelter to the Year 2000 (Nairobi, 1991) (HS/266/91E).

2. Tanzania Sensa 1988 - Preliminary report.

3. Jill, W. and others. Links between Population, Settlements, and the Environment: The provision of organic materials for shelter. South Bank University, London 1994.

4. United Nations Centre for Human Settlements. (Habitat), The use of selected indigenous building materials with potential for wide applications in developing countries, Nairobi 1985.

5. Roland, S. and others. Appropriate Building Materials, A catalogue of Potential Solutions St. Gallen, May 1988.