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close this bookJournal of the Network of African Countries on Local Building Materials and Technologies - Volume 1, Number 4 (HABITAT, 1991, 48 p.)
View the document(introduction...)
View the documentContributions to the Journal
View the documentForeword
View the documentHousing in Africa, problems, prospects and strategies*
View the documentKenya: Towards the development of a national code of practice for structural masonry - the Kenyan approach*
View the documentNigeria: Research and development in the promotion of standards and specifications for stabilized soil blocks*
View the documentEthiopia: Light-weight concrete made with Ethiopian pumice*
View the documentMauritius: Use of calcarenite blocks in housing construction in Rodrigues*
View the documentGhana: Optimum firing temperature for some clay bricks*
View the documentEthiopia: Construction of mud houses - an alternative to the traditional methods of house construction*
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Ethiopia: Construction of mud houses - an alternative to the traditional methods of house construction*

* By Marius Biering, AMBO Junior College of Agriculture, P.O. Box 19, Ambo, Shoa, Ethiopia.
* Photographs by Andreas Depping.

Introduction

It is a well-known fact that the housing shortage in developing countries is a serious problem, especially in Ethiopia, where according to the United Nations housing classification system, 80 per cent of all dwellings are categorized as slums.

In 1986, the Building College of Addis Ababa made a survey among dwellers in Ambo, a medium-sized town in the Ethiopian highlands. The aim of the investigation was to identify the problems confronting the housing sector.


Question: Which position has the housing problem amongst the other problems?

Some 50 per cent of people interviewed classified the housing problem as the most crucial one which is a clear signal for policy-makers to establish strategies to deal with the situation.


Figure 1. The traditional building method requires a lot of wood for the construction of walls. Wood has been replaced by mud blocks.

In order to tackle the problem, a concept of low-cost building construction, based on mud as the main building material, was developed. The concept aims at replacing wood by mud, which ultimately would help to reestablish the ecological balance through the protection of natural forests.

The concept reduces the cost of construction to a minimum by using mainly locally available building materials (soil, stones, straw and water). Moreover, by introducing simplified working conditions, and equipment through self-help share for labour input, the technology is gaining popularity among the low-income population.

Mud technology opens ways for small-scale entrepreneurs who do not require high investments and skills. It suits the environmental conditions of the highlands and uses labour and building materials in the optimum way.

Brief description of the technology

Foundation: A stable load-bearing foundation is an indispensable precondition for a durable mud wall. A so called three-layer mud foundation has been introduced - the depth of which depends on the local circumstances and soil conditions.

Figure 2 shows a typical three layer foundation.


Figure 2. The three-layer mud foundation.

Walls: Blocks are produced by using soil, teffstraw and water. Two types of blocks are produced, namely: full-blocks and hollow-blocks (52x26x20 cm). The moulds for producing blocks are simple wooden frames, developed at the Burayu Basic Technology Centre in Addis Ababa. Figure 3 shows the two types of blocks.


Figure 3. Full and hollow mud-blocks.

The wall is constructed following the normal practice of bricklaying. The mortar used between the layers has the same mixture as for blocks without any additional stabilizing admixtures.

The first metre of the external walls is constructed with fullblocks and the rest of the external and all internal walls are built using hollow blocks. This method helps decrease the use of unnecessary amount of material.

The outside plastering of the walls consists of two layers and has a height of 1.2 m. This double-plaster makes the wall flush with the foundation and protects the weather side of the walls against damage caused by heavy rains.

Figure 4 shows a cross-section of a mud wall with details of layers and plastering.


Figure 4. Cross-section of an external mud block wall.

Roof: The roof structure is firmly connected with the walls by means of metal strips.


Figure 5. The roof is fixed to the wall with metal strips.

The roof should have an overhang of at least 1 m to protect the mud wall against rain. The external walls are normally 2.4 m in height.


Figure 6. A roof overhang is very important for the protection of the walls.

In order to cover the roof structure and also improve the indoor climatic conditions, bamboo and grass mats are used as main materials. Figure 7a shows a typical ceiling.


Figure 7a. The grass-mat ceiling.

Some details of the concept

Ceiling: The mud blocks are turned 90 degrees at the twelfth layer and become a projection in the wall. On this projection, bamboo is layed and covered with grass mats. By doing so, in addition to having a flat ceiling, the climatic conditions inside the house are improved considerably.

Floor: The natural soil is removed to a depth of 30 cm and, after levelling the surface, one layer of full mud blocks is placed. The blocks are covered with mud plaster to give a level surface. Figure 7b shows a typical mud block floor.


Figure 7b. The mud block floor.

Drainage ditches: As part of the final construction works, drainage ditches are dug to facilitate evacuation of surface water accumulated during rainy hours from the walls and foundation. Figure 8 shows a drainage system.


Figure 8. An effective drainage system is important.

Demonstration houses: After constructing several demonstration houses in urban and rural areas, officials from Ambo showed keen interest in the technology and asked for assistance in the development of larger projects. Following a series of discussions, a town development project was designed in three phases.

Phase 1: Setting up a mud-block producing plant near Ambo town.

Phase 2: Construction of four mud model houses in the poorest districts of the town. Establishment of an attractive production and selling system with a flexible price policy.

Phase 3: Providing support to private and governmental housing programmes and handing over the mud-block production plant to the Municipality of Ambo.


Figure 9. The Ambo mud-block production plant.

Different tasks of the Ambo mud-block production plant

The tasks of the plant are clearly defined as follows:

(a) Production of high quality mud blocks;

(b) Selling of building materials (blocks, soil, sand and stones);

(c) Providing consultancy to people and/or institutions of the town in all aspects of mud construction;

(d) Training of technicians through a long-term programme, who would become contractors for mud construction;

(e) Provision of supervisory services during construction;

(f) Maintenance and repair of houses.


Figure 10. Training is an important aspect of the Ambo mud-block factory.

Some results of the research

Besides the normal project activities, and on the basis of research and tests, practical data have been collected on different types of soils. Table 1 shows some characteristics of blocks.

Table 1. Characteristics of mud-block production

Category
Soil class

I
Loam

II
Clay loam

III
Clay

Water in 1 per m3 soil

350

450

750

Straw in kg per m3 soil

4

5

10

Number of blocks produced out of 1 m3 soil (52x26x20 cm)


- Mud full blocks

23

27

-


- Mud hollow blocks

33

37

34

Drying time in days until

Hollow blocks

Hollow blocks

Full blocks


- Removing of blocks from production place

8

10

15


- Wall construction

30

40

60

Weight of dry blocks in kg


- Mud full blocks

43

35

25


- Mud hollow blocks

29

23

20

Mixing time until the mud is ready for the production of blocks (days)

4-5

7-8

12-15

Comparison of the compressive strength of unstabilized mud hollow and mud full blocks with the compressive strength of concrete hollow-blocks (according to the National Standard of Ethiopia)

Basic research on the application of mud without stabilizer for house construction was carried out. A considerable amount of samples and data, which gave a clear idea about the quality of different mud mixtures and mud blocks, were collected.

The dry compressive strength of mud blocks produced out of suitable soils can be compared with the strength of concrete hollow blocks. This result shows that mud is not only a cheap building material but, also, a building material of acceptable quality. Table 2 shows the results of tests carried out on mud blocks.


Table 2. Comparison of the compressive strength

1 Average compressive strength of concrete hollow blocks of four block factories in and around Addis Ababa tested by Materials Research and Testing Department (1964-1967),

Comparison of the work organization, the transport requirements and the cost of construction

Building materials like cement, wood or concrete hollow blocks are very scarce, especially outside the capital city, Addis Ababa. In addition to the shortage problem, purchasing of large quantities of cement, for example, requires official permission which is difficult to obtain.

Table 3 illustrates comparison of various worksteps required for three different types of wall construction.

Table 3. Work organization

Type of wall

Chika-block wall

Traditional wall

Cement-block wall

Soil, straw, water

Wood

Cement, sand, water

1. Mixture of mud

1. Cutting

1. Mixture of mortar

2. Production of blocks

2. Splitting of wood


3. Construction of wall

3. Construction of wooden structures

Cement blocks

4. Plastering of the wall


2. Construction of wall


Soil, straw, water

3. Watering of wall


4. Mixture of mud

4. Mixture of plaster mortar


5. Plastering of the wooden structure

5. Plastering



6. Watering of plaster

Materials

Soil

Straw

Water

Wood

Soil

Straw

Water

Cement block

Cement

Sand

Water

Availability

+

+

+

P/O

+

+

+

O

P/O

+

+

+ = Available on the spot or in the surrounding area
O = Hardly available, scarce building materials
P = Permission necessary
NM = Non-motorized
M = Motorized.

As indicated earlier, the mud technology for house construction involves mainly local materials and uses a considerable labour force, thus, making the construction cheaper than other methods and creating employment opportunities among the rural population.

A cost analysis shows that, in the case of a wall constructed of concrete hollow blocks, the expenses for labour are 20 per cent of the total cost of the wall, and the rest is made up of the expenses for material and transportation, whereas in the case of mud walls that same percentage is 86 per cent.

Figure 11 shows the percentages of expenses of three different types of walls.


Figure 11. Percentages of expenses for three different types of walls.

Available publications of the Ambo Junior College of Agriculture (AJCA) and the Municipality of Ambo (MoA)

1. Marius Bierig, Construction of Houses out of Mud (AJCA, 1988).

2. Marius Bierig, Extension Activities of the Appropriate Technology Center of the Ambo Junior College of Agriculture (AJCA, 1988).

3. Marius Bierig, “The ISLAND, informally trained daily labourer founded the self-helping group ISLAND”, Report on building activities (1989).

4. Marius Bierig, Report on the Implementing Phase of the Ambo Mud Block Factory (MoA, 1989).

5. Marius Bierig, The Theory of Mud Technology without Stabilizers, a manual for the training of mud technicians, (MoA, 1989).

6. Marius Bierig, Basic Research about the Application of Mud without Stabilizers for House Construction Purposes (AJCA, 1989).

Reports can be ordered through:

Appropriate Technology Centre of the Ambo Junior College of Agriculture
P.O. Box 19
Ambo, Shoa, Ethiopia

or:

German Volunteer Service
P.O. Box 2725
Addis Ababa
Ethiopia.