Traditional Building Methods in Northern Ghana
1.0 Indigenous Building Methods in Northern Ghana
1.1 Traditional Building Methods in the Northeast of Ghana
1.2 Traditional Building Methods in the Northwest of Ghana
In the dry and northern half of Ghana the traditional building methods in mud are still followed throughout the region, mainly in the rural areas. In the north-eastern half of this area the buildings are circular and arranged as cells around an inner yard. The maximum compressive strength of mud as a homogenous material is achieved through the circular shape of the load-bearing walls. Roofs are built conical and thatched over rafters or as flat mud roofs with a mud parapet. In the western, predominantly Moslem half of the region, rectilinear structures of interconnected cellular spaces are built with flat mud roofs. In the Lobi area (Map No.4) these roofs are supported by posts, beams and rafters. The mud walls are not load-bearing like in the other areas of the region. In the remaining areas of the region one finds a combination of the two main layouts. There are also Fulani settlements in places with circular huts constructed from grass-woven mats tied to posts with conical thatched roofs from the same materials. In the district and regional centres of the area most of the buildings are built with cement-sand blocks, reinforced concrete structural framework, floor slabs, ceilings and corrugated iron, aluminium or asbestos-cement roofing sheets over a timber substructure. The plans of the buildings are rectangular. The rectangular layout for building has also been introduced in those rural areas where the traditional layout was circular. Yet the traditional building method with wet mud walls moulded into layers achieves its best structural strength through the circular form. In the rectangular shape erosion with resulting disintegration starts at the corners of such structures.
1.1 Traditional Building Methods in the Northeast of Ghana
1. HOUSE CONSTRUCTION
The materials used and the resulting form of the traditional buildings point to different socio-economic organizations, activities and religious beliefs of the people in this region. This is also reflected in the time for building activities. In the case of the Dagombas (and also Mamprusis and Konkombas) where most of the yam in this region is grown, the months of March and April are “building months”. In the other areas building activity may commence on the on-set of the dry season in November and last until March, especially in places where extensive decorations are applied to the freshly plastered walls (Fig. 10).
The men are the builders. They build the walls and roofs of the buildings. Women begin the building activity, after the Tindana (the Earth’s custodian) has performed the appropriate ritual on the chosen site (in the non-Christian and non-Moslem areas), by weeding and sweeping the space marked out by the compound owner for the building. The swept site is then watered thoroughly. After the men have completed the wall construction and built the roof (a co-operative effort by the clans), the women plaster the in-and outside of the buildings, lay and beat the floor and apply decorative finishes to the walls. The Dagombas and Gonjas do not plaster their buildings; decorations are applied only around door openings. Their structures have a much shorter life span (about 4 years, unless annually maintained). A plastered and therefore protected mud structure will last a long time. Plaster is repaired and decorations are normally renewed every 4 to 5 years. Roofs have to be annually maintained in all structures.
Laterite or soils containing clay (dug from pits near the building site) or alluvial soil from riverbanks are used as material. Organic matter and stones are removed. The material is then mixed with water, kneaded (with feet) until it is smooth (Fig.11). Fine, sharp river sand or gravel may be added as a form of aggregate. The material is then rolled and formed into balls (Fig.12). In some areas the wall will have a small foundation, dug about 150 to 300mm deep, rammed and filled with stones or a first layer of mud balls. In other places the wall is started on the swept and wetted ground. It is constructed in layers, each approximately 300 to 400mm high from a thickness of about 350mm at the foot of the wall to 200mm at the top. The mud balls are worked and moulded by hand and the top for bonding with the next layer (Fig.13), normally laid the next day after the first layer has been allowed to settle and dry.
The traditional circular house has no door. The entrance into the house is an opening, cut into the wall with a cutlass by the builder after the construction of the wall has been completed. The ethnic groups have different sizes and shapes of openings as can be seen from the illustrations (Fig.14 and Fig.15). In some cases already timber door frames are fitted into the wall during construction to receive door stops and an inward opening boarded door of about 1.50m height (Fig.16).
The traditional round house has no windows. Ventilation is achieved by lifting the “roof skin” with a bent wooden piece in form of a knee which is inserted under the roof on top of the mud wall opposite or above the entrance opening (Fig.17) In the case of a flat mud roof a clay pot without bottom is inserted into the mud layer during construction of the roof, also at a position opposite or above the entrance opening. The top of the pot can be covered with a calabash or another pot during rain. Both “openings” admit light and achieve vertical ventilation through the stack effect. In rectilinear structures in some areas small wooden framed and boarded windows have been introduced (Fig.18 and Fig. 19)
1. THATCH ROOF
This refers in most cases to the conical thatch roof over a round house, but in some places of the region (especially in the Nabdam and Kusasi ethnic areas along the Bolgatanga-Bawku road) to a thatch roof with ridge over a rectangular house.
Due to the limited structural properties of the materials used roof spans are rather short; buildings normally have a width or diameter of around 3 metres. This can be extended by introducing different methods of support.
The traditional conical thatch roof (Fig.20) has a substructure of four main bush pole rafters (normally from the Shea-butter tree - Butyrospermum Parki – a heavy termite-proof timber) about 2.5m long and 75mm in diameter bedded into the top of the wall, forked and tied at the top ends with Kenaf fibres. These rafters form a radial frame together with smaller rafters (of 45mm diameter). They are stabilized by a number of 50mm diameter grass-rope purlins or purlins roped similarly from young Nim tree branches (Azadirachta Indica) tied together and to the rafters with kenaf fibres. The lower third of the roof is then covered with a Zana-mat (Fig.21) which is woven from grass (Andropogon Gayanus) a grass growing up to 3.5m in length in the coastal and interior savannahs and used in the North for weaving rough mat walls, screens for openings and protection against wind etc.). On top of the Zana-mat the roof thatch (from dried spear grass – Heteropogon Contortus, or another common savannah grass – Imperata Cylindrica) is laid in layers, “sewn” with Kenaf fibres through the Zana-mat to purlin ropes and rafters. The thatch is tied together at the apex, sometimes kept fixed into place with a bowl without bottom or an overturned pot or grass ropes and sticks (Fig.22). The upper layer of the thatch near the apex is in some areas again a Zana-mat.
The largest safe span of a conical roof constructed in this fashion is 4-5 metres, with an additional centre support in form of a post which is placed beneath the junction of the rafters. Large rooms are rare, however, since it would already be difficult to find the necessary longer rafters for such span.
2. THE FLAT MUD ROOF
this type of roof is built by the Talensi (Fig.23), Frafras, Nanakansis (Fig.24 and Fig.25), Kasenas and Builsas, as well as by the people living in the north-western part of the region (described separately). The walls are load-bearing, they fully support the roof beams, except in places like the roofed-over wet season kitchen of the Nankansis which is built against another house.
Timber used for construction is from the Shea-butter tree, which is termite-proof. One layer of beam-poles is supported on the wall, thinner rafters are laid across these about 100mm apart. On top of this layer small pieces of split poles or twigs are laid in a cross-wise direction, very close together. The next layer is about 250mm thick from well-kneaded mud clay. The finish is a screed of a mixture of mud or clay, fine sand, cow-dung and the residual meal from the Shea-butter-nut during extraction. The surface is finished off with a varnish which is produced by boiling the empty pods of the Dawa-Dawa tree (West African Locust Bean tree, Parkia Clappertoniana). The mud layer of the roof is given a fall, so that the roof sheds rainwater easily through spouts (from metal sheets, wood or openings left in the wall. A parapet wall from mud is built around the roof. The roof is, in many areas, used for storage as well as for sleeping during the hot months at the end of the dry season (March, April).
Walls are plastered in and outside with a mixture of cow-dung and the juice from the boiled, empty Locust Bean tree pods (Figs.26, 27, 28, 29). This extract (sometimes the bark is also boiled in addition) acts as a plaster hardener and stabilizer, and forms a firm waterproof layer on the external surface, when it is sprayed on with a brush after plastering. The wall finish, as mentioned before, is the work of women, who have, in different ethnic groups, developed high artistic skills in decorating the finished walls. These decorations are incised patterns (applied with flat or pointed pebbles or fingers), moulded, painted or a combination of different techniques (Fig.30). Dagombas and Konkombas have no surface decoration, but embed cowrie-shells or broken china (or whole plates) into the mud above the entrance opening to the round house or embellish the complete openings. In Dagombaland this decoration symbolizes the house owner’s wealth. Openings which are to receive such decorative treatment are first plastered (mixture of mud and cow-dung, Fig.31 and Fig.32). Another method of finishing a wall is used by the Konkombas. They grind shells collected from the banks of the river Oti (which passes through their area) and mix the obtained lime with cow-dung. This “limewash” hardens the surface of the walls, makes it impervious to rain and gives the Konkomba houses their characteristic white, rather concrete-like appearance.
In the Nankansi area the women decorators polish the painted surface of the wall with flat stones (granite or pebbles), until the appearance is that of a wall painted with glossy oil paint (Fig.33 and Fig.34).
The last job is the laying and finishing of the floor. This work is again done by the women if the compound and it extends to laying the floor not only in the rooms but also in the actual compound yard outside the houses up to the walls which encircle the inner yard of the compound in which the granaries are placed and sheep, goats, cows and poultry stay during the night. Mud or laterite is mixed with fine sand collected from riversides. Cow-dung solution or in some places a mixture of sand and cement is sprinkled over this layer of mud or laterite (average screed thickness about 20 to 40mm) which is laid straight on the swept and wetted ground. The cow-dung solution has been left to soak in water for about three days. A group of women then beat the floor with special wooden implements or flat stones in unison amidst singing, for about two to three hours (Fig.35). The resulting floor finish is a smooth, hardwearing surface. The extract from the boiled empty pods or bark of the Locust Bean tree is sprinkled daily on to the finished floor for two weeks. This hardens the surface further, makes it waterproof and at the same time gives it a pleasant, rustic, reddish appearance. The outside floor is laid to fall to enable surface water to drain off easily, usually through an opening at the base of a bathroom wall to the outside of the compound.
3. FULANI COMPOUNDS
In some areas of the north Fulanis (who are nomads) have settled; they still pursue their traditional profession as cattle herders. One can find their settlements in Zongo-sections of Bolgatanga, Tamale, Bawku or in villages in which cattle are raised.
Their house structures are different from those of the host villages or towns in which they live. The structures reflect their lifestyle. Although they may have settled permanently in the chosen area, their houses appear like large tents. Wooden poles are anchored into the ground, arched over to meet and be fixed at the apex (the layout is more or less circular). This structural framework is covered on the out-and inside with rough woven grass mats (Zana-mats) held in place with branches and mud. Towards the apex layers of thatch are added on top of the mats similar to the indigenous conical thatch roof finish. From the outside such a house resembles the traditional circular building but its structural system is completely different; it reflects a lightweight shelter which can easily be removed and assembled elsewhere (Fig.36). The arrangement of individual compound units placed around an internal courtyard is similar to the compound arrangements in the northern part of the region; their linking walls are also made from woven grass mats.
The importance attached to the place in which the basic food items are stored which the northern farmer harvests from his farm can be seen from the high level of proficiency in the indigenous construction methods used for the construction of granaries (silos, barns). Maize, millet, guinea corn and rice are stored in these structures. In areas where the animistic tradition is still followed the main granary of the compound is the place in which the soul of the compound owner lives during his lifetime. It is the location of this granary which is fixed by the Tindana (or Earth’s custodian) first and all the other buildings of the compound are laid out in relation to it. This tradition is still followed, as investigations in the field revealed, even in areas where Christianity has penetrated.
The granaries are built from wet mud in the same way as the circular houses are built, on top of a well designed foundation from large stones (solid) or stones together with a system of cross beams from the Shea butter tree on top (to allow ventilation to pass under the silo). The walls taper off towards the opening at the top which is covered with a woven thatch “lid” (Fig.37 and Fig.38). The average capacity of the mud silos is 11/2 to 2 tons – the Frafras, Kusasis and Builsas have built silos with larger capacities. The Konkomba silos (for threshed and unthreshed grains) are distinctive structures (Fig.39). They are built in large pot form from coarse woven basket work which is thickly covered with a mixture of soft mud and cow-dung on both side. They are supported on three or four large granite blocks with a flat stone as base laid over. The externally applied thick solution of mud and cow-dung is also smeared over the base stones. The outside of the granary is finished with limewash (the lime is obtained from grinding rivershells). In the interior of the silo divider walls of mud (about 100mm thick) are built for stabilization of the structure. The Konkomba silos are larger than the similarly constructed Mamprusi basket granaries. The circular barns of the Mamprusi and Dagombas (as well as those of the Gonjas) are built for the storage of unshelled late-millet, guinea corn, bambara beans, yam and sweat potatoes. The grain is not stored for very long in these barns (Fig.40). It is removed as the threshing proceeds and then transferred to the permanent grenary. Normally four large granite stones (placed to form a square inside a marked circle) carry a wooden platform from bush poles. About 12 poles with forked top ends are dug into the ground around the platform. At the top they are tied to a thick grass rope (which acts as “well plate”). The inside (floor and wall) is covered with coarse woven grass mats which are fixed to the poles. An additional thick woven grass mat is laid on the floor. The thatch roof is built in the same way as has already been described.
1.2 Traditional Building Methods in the Northwest of Ghana
In this area of the country-floor plans of buildings are more or less rectangular. In the Lobi-house with its covered internal courtyard, walls are laid out rectilinear to enclose interconnecting spaces. They are built in the same way as the circular house walls in the North-east of Ghana, that is: moulded in layers with wet mud balls or with sun-dried mud bricks or in some cases also with dried mud clods from old, broken down buildings. The walls are however, thicker (average 400mm). The separate layers, if built with mud balls, are clearly recognizable, since the next layer overlaps the previous layer so that the external appearance (the inside walls are plastered and finished smoothly) is that of an exaggerated horizontal feather-edge boarding (Fig.42 and Fig.43). The Lobis support the flat mud roof entirely with a post and beam arrangement (which will be explained later). The walls are therefore not load bearing. Room widths do not exceed 2.5 to 3 metres. Each room is in itself an independent structural entity, as can be seen from the part-plan of a Lobi house (Fig.44). It is easy to understand the internal layout of such a house when one stands on the flat roof. The non-load bearing walls project in the form of parapets (about 250 to 300mm high) beyond the roof surface (Fig.45). The Lobi house walls are exposed to fewer ethnic groups in the area, where the flat mud roof is supported on these walls with its beams and rafters bedded into the mud of the wall. Corners of such buildings, unless reinforced cannot transmit the forces to which the walls are subjected. Early deterioration is the result. From the 16th century onwards when Islam was introduced in West Africa and also in the present North-west region of Ghana through traders and migrants from North Africa and the Sahel area the method of constructing heavy buttresses to reinforce wall corners and walls found its way into this area with the mosque buildings (Fig.46) and was also adopted by most of the people along the present Lawra-Wa-Bole-Bamboi road, part of the historic north-south trade route, with exception of the Lobis (Fig.47). From this it can be seen that “foreign influence” in the North is restricted to a comparatively small area. A combination of both construction methods has developed at the same time and can be found in the buildings of the Gonjas, Dagartis, Walas and others.
DOORS AND WINDOWS
Due to the linear layout of the buildings in this part of Ghana entrance openings to rooms (or to the house in the case of the Lobis) are more or less rectangular. They are covered or closed with thick mats woven from grass (similar to the Zana-mats), or have already a doorframe with an inward opening boarded door (Fig.48). Windows were not normally part of the traditional house or compound. They have been introduced during the last 25 years. Own field studies undertaken in the area in 1961 showed very small window openings (boarded casement windows in a timber frame) in some houses of the Gonjas, Walas, Dagartis and Lobis. During the documentation survey which the Department of Architecture students undertook in 1975 in Gwollu in the Northwest of Ghana close to the border with Upper Volta, it was found that nearly all buildings in this rural community had small windows.
As already described under “Walls” the flat mud roofs (the conical thatch roof, which is quite alien to this region, is found occasionally in Lobi compounds) are built with a supporting bush pole substructure of posts and beams or beams and rafters from the Shea butter tree bedded into the mud wall. The posts have forked ends at the top and carry the beams. Across these are laid smaller poles (rafter) at the distance of 100mm apart in two layers. Over these follows a layer of crosswise arranged, closely laid twigs or small split poles. A layer of about 200mm thick well kneaded mud or clayey soil is put on top of this. A finish of a mixture of mud, cow-dung, sand and the residue from Shea butter during extraction is applied to the mud layer and brushed with the liquid obtained from boiling the Locust Bean tree pods. A pot without bottom is inserted into the mud roof in places to let in light or for extraction of smoke. It can be covered with a calabash or bowl during rain. The mud roofs are laid such that they drain off rainwater easily through spouts let into the small parapet wall which normally surrounds the roof (Fig.49).
Only in areas where cattle are raised is cow-dung available as the smooth cohesive agent for the traditional mud plaster, and this applies only to a part of the region. For example the Gonjas, who do not have cattle, will only apply an additional mud coat to the completed walls. The Lobis finish their external walls smoothly during building in the described overlapping fashion. Due to the absence of proper plastering buildings tend to deteriorate quicker than in the Northeast of Ghana and need very regular maintenance. The only decorative treatment of wall surfaces in form of “herring-bone” or round patterns is applied with fingers by the Gonja women into the rendered walls, especially around door openings. The Sisalas and Walas use decorations over door lintels or in the roof parapet by arranging sun-dried mud bricks in such a way that they form triangles (which can also be found over the entrance into the mosques in this area) which give the appearance of a “perforated” wall.
The floor finish is applied quite similar to that in the northeastern part of the country, and also beaten with wooden implements or with wooden rams by the women of the compound builder’s family.
With the exception of the Lobi silos the granaries in this area are not of such striking features as those of the Frafras, Konkombas or Kusasis in the Northeast of the country. The Gonja farmer grows mainly guinea corn and groundnuts. The large circular barns for storing the unthreshed corn are placed near the farm and built from grass mats similar to the Dagomba barns. In the compound the threshed corn is stored in large baskets inside a store and the groundnuts in small baskets, smeared in and outside with mud and covered with thatch, which are placed on wooden platforms inside the compound yard. The Lobis build cylindrical granaries over a square base tapering off towards the top, from a thick mixture of mud, cow-dung and crushed straw (from dried guinea corn or millet stalks). The neck is covered with a thatch “hat”. They locate the granary outside the external compound wall. A roof is built around the neck of the granary (threshed grain is stored and taken out from the top). Like this the granary is incorporated into the house when new rooms are added to it . Similar to the Konkomba granaries divider walls which at the same time act as reinforcement of the granary are built inside. For the unthreshed corn square mud silos covered with thatch roof are built near the farm (Fig.52).
In the Savannah mud has always been a universal building material, its plastic form and moulded application resulting in a unique architecture. In addition the circular mud wall is a structure which consequently achieves the fundamental principle of building construction: The stability of the structure.
Since building is a co-operative effort of the whole family or clan in this area, the technology with which this is achieved is known to everybody. A farmer does not engage skilled or specialized craftsmen to build his house. He and his brothers and sons are skilled themselves. And to what high level can be seen from the optimum use of mud as structural material in the building of his granaries, especially among the Konkombas, Frafras, Kusasis, Builsas, Mamprusis and Lobis.
Article and illustrations by Hannah Schreckenbach (extracted from her book "Construction Technology for a Developing Country", GTZ publications, 1983, pp 21-72 http://www.gtz.de/basin )