Promoting and testing low Cost Housing Techniques: Latex Concrete Habitat

In January 2005, AIZON's founders undertook a trip to the US to look at a low cost construction technology developed in Colorado. As the techniques developed in the US seem appropriate for Ethiopia and respond to the need for low cost housing as well as for establishing a library, further design work and field testing were conducted in Ethiopia. The technologies best appropriate for low cost housing in Ethiopia are a combination of latex concrete habitat and Adobe construction.

1. Latex Concrete Habitat

Thin shell latex concrete roof have been developed to answer low cost construction requirements in poor regions where the need for cheap housing abounds (such as in the southwestern region of the United States) or to provide immediate shelter to displaced population groups . Thin shell latex concrete surfaces are light weight, portable and strong. These shells structures bear their loads in tension and compression in their surface and hence do not need to be heavy and thick. The light weight of the thin shells means that they can be mounted on any combination of walls (conventional bricks or HCB structures, Adobe blocks, wooden/iron poles, etc...). This method also entails the lowest cost in materials of any form of construction due to the fact that very little material is actually used. The latex concrete shells are safe, permanent, versatile and require little maintenance. They can be constructed rapidly by unskilled labour.

The latex concrete techniques require Portland cement, latex liquid and fiber glass fabric, all of which are readily available in Ethiopia. The estimated cost of material for thin shell concrete roofing in Ethiopia is below 40 Birr ($ 4.6) per square meter, which is the lowest of all construction materials used in the country.

Albert Knott and George Nez, “Latex Concrete Habitat”, Canada, 2005.

Figure 1: Four segments of latex concrete on existing wall (model)

Figure 2: Latex concrete roof build in Afghanistan and placed on existing mud walls for a school

Albert Knott and George Nez, Ibid.,, 2005.
Albert Knott and George Nez, Ibid.,, 2005.

The figures above show a four segment of latex concrete on an existing wall (model) and a latex concrete roof built in Afghanistan and placed on existing mud walls for a school (figure 2).

The construction of Yebelsa library in Bahar Dar/Ethiopia will use the latex concrete technology for roofing and Adobe blocks for walls or simple wooden columns for open reading areas.

2. Adobe Construction

Adobe is one of the oldest building materials in use. Adobe soil has clay and sand in such proportions that when mixed into mud then dried out it forms a brick or a wall. The best adobe soil will have between 15% and 30% clay in it to bind the material together, with the rest being mostly sand or larger aggregate. Too much clay will shrink and crack excessively; too little will allow fragmentation. An adobe brick is made of adobe soil and is sun cured on the ground. Chopped straw or other fibers are usually added to adobe for strength. Commonly adobe is shaped into uniform blocks that can be stacked like bricks to form walls. A mold block developed by Salam Children Village has been successfully tested by AIZON P.L.C. in Bahar Dar. Adobe mortar is used to cement adobe bricks together to create a wall. Some adobe buildings have been plastered with Portland cement on the outside in an attempt to protect the adobe, but this practice has led to failures when moisture finds a way through a crack in the cement and then can not readily evaporate. When adobe is used as an exterior plaster it is stabilized. Portland cement can be used for inside plastering.

In the past decade, Adobe construction techniques have seen strong interest in the United States in particular with the publication of numerous books on Adobe house construction and actual residential construction in various cities. Compared to HCB construction, Adobe provides better thermal regulation and therefore more comfort in the building.

Adobe buildings that have substantial eaves to protect the walls and foundations to keep the adobe off the ground will require less maintenance than if the walls are left unprotected. Adobe stands forever if it has a good foundation, a good roof and has occupants who give it of periodic maintenance. The oldest churches in Ethiopia demonstrate the long lasting properties of Adobe.

3. Promotion of Adobe Block Construction

AIZON has lobbied the Municipality in Bahar Dar to consider allowing the construction of Adobe house to facilitate low cost housing for poor urban and sub-urban population. Until recently, the Amhara regional government did not authorize “Adobe/mud houses” construction within the boundaries of the city. However, following a meeting held on the 19th of June 2005, the regional government has announced that Adobe house will be permitted. AIZON provided technical guidance to the relevant departments for the development of minimum standards regulating mud house construction, using mud blocs.

AIZON has successfully built a round tukkul to be used as a store and field office at the arboretum site using the Adobe block technique in Bahar Dar. The construction has initiated interest amongst the poorer residents of Bahar Dar.

	View of the round tukkul under construction, using Adobe block (before plastering, May 2006)
Outside view of the tukkul under construction, using Adobe blocks and traditional church design, May 2006.
Outside view of the tukkul under construction, using Adobe blocks and traditional church design, July 2006.