Roofing in West Africa

West Africa stretches from the edge of the Sahara through the Sahel and the Sudanian savanna to the humid forests and lagoons of the Gulf of Guinea. Its traditional roofs follow that climatic gradient. In the dry north, builders made flat or gently domed roofs of earth on timber, and in Hausa cities they developed earth vaults and domes; in the savanna and forest belts, steep thatched roofs of grass and palm sat on round or rectangular houses. Over the 20th century, corrugated metal sheet replaced thatch on many traditional buildings, and cement and concrete increasingly replace earth.¹⁴ The region spans Senegal, the Gambia, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Côte d'Ivoire, Mali, Burkina Faso, Ghana, Togo, Benin, Niger and Nigeria, along with Mauritania and Cabo Verde.

Climate and hazards

Long-spanning timber is scarce across much of the region, which shaped roof structure: in drier areas, roofs rest on buttresses, large posts and earth reinforced with bound saplings or tree trunks, while along the coast and in Guinea, where trees are plentiful, roofs are thatched with palm fronds.⁸ Earth roofs and walls are vulnerable to rain, leaching, erosion and gullying, and must be replastered regularly.¹²

Sahelian earth roofs

Mali: Djenné

In the Sudano-Sahelian building tradition, walls are made of sun-dried earth bricks and earth plaster, the technique known in French as banco.¹¹ Djenné in Mali is the best-known example: its old town, a UNESCO World Heritage Site since 1988, retains about 2,000 traditional earth houses.¹² Houses have flat roofs, and ceramic pipes project from the parapets to throw rainwater clear of the walls.² Hand-shaped cylindrical earth bricks (djenné ferey) were used in the archaeological structures, and rectangular bricks replaced them during the colonial period in the 1920s.¹²

Djenné's earliest settlement dates to the 3rd century BCE, and the first mosque on the site of the present one was built in the 13th century.² The Great Mosque of Djenné, the third mosque on the site, was rebuilt in 1906–1907 on a raised platform to protect it from floods.¹² Its earthen roof rests on a palm-wood structure and is pierced by 105 skylights for light and ventilation, while palm-wood projections from the walls serve as permanent scaffolding for replastering.² Each year, usually in April, the town's four quarters prepare mud plaster mixed with rice husks, and about 40 masons, helped by the whole community, can replaster the building in roughly half a day.² Threats to Djenné's architecture include uncontrolled urban growth and the replacement of earth with cement, fired brick and metal doors and windows.¹

Togo and Benin: Koutammakou

In the Koutammakou landscape of north-eastern Togo and north-western Benin, the Batammariba build takienta, two-storey earth tower-houses on circular or elliptical plans that serve as family homes and places of ancestor worship, with granaries on the roof terrace and animals on the ground floor.⁵ The Atacora Mountains dominate much of this landscape.⁵ The Togolese part was inscribed on the World Heritage List in 2004.⁵ Wood and straw are becoming hard to find near the villages, and many newer houses have metal roofs.⁵

Burkina Faso: Kassena houses of Tiébélé

The Kassena compounds of southern Burkina Faso, best known from the royal court at Tiébélé, have flat earth roofs that serve as terraces for drying grain and for sleeping in hot weather.¹³ The roof is built up on a timber structure: a layer of mud, then dry laterite pressed down with a stick, then mud mixed with cow dung, each layer compacted in turn.¹³ Such roofs resist rain well but need replastering roughly every five years, while the painted walls below are renewed every few years, usually after harvest and before the rains.¹³

Nigeria and Niger: Hausa vaults and domes

Hausa builders of northern Nigeria and southern Niger developed a sophisticated system of flat roofs, vaults and domes in earth and timber. Walls were built of tubali, conical or egg-shaped earth bricks laid in mud mortar and plastered with swamp mud.³ Roofs used azara, split deleb palm wood, which is light for its length, resists termites and bonds well with mud.³

To span wider rooms, masons cantilevered successive lengths of azara from opposite walls at decreasing angles, roughly 0.5, 0.75, 1 and 1.5 m (1.6, 2.5, 3.3 and 4.9 ft) long, binding them with cord and coating them with mud until the two halves met to form an arch (kafa).³ Domes (tulluwa) rose without formwork on intersecting half-arches and were finished with mud mortar.³ A dome at Kafin Madaki built in 1861 measures about 8.2 × 8.65 m (27 × 28 ft), and one in the Kano palace built in 1935 about 7.5 × 8.25 m (25 × 27 ft).³ The Friday Mosque of Zaria, built in 1840 by the master builder Malam Mukhaila Dugura, has domed bays carried on massive piers and arches spanning more than 8 m (26 ft).³

Hausa roofs were waterproofed with laso, a local plaster made from dye-pit residue, indigo liquor, ash and a sticky plant extract, which stays watertight for about five years before it must be reapplied.³ Projecting spouts and eaves (indororo) carried rainwater away, and pinnacles called zankwaye rose above the parapets, mainly for decorative and symbolic reasons.³ Wealthy compounds sometimes had a second storey built on the same principles with lighter materials.³ Builders were organised under a chief of builders (Sarkin Magina), and master builders trained through an apprenticeship of about ten years.³

Savanna and forest: thatch

Ghana: Asante

The traditional Asante buildings near Kumasi, Ghana, built between the late 18th and late 19th centuries, were made of timber, bamboo and mud plaster with steeply pitched roofs thatched with palm fronds.⁴ By the time they were protected, 12 of the 13 surviving buildings had had their thatch replaced with lighter, lower-pitched corrugated iron roofs, a change that illustrates the region-wide shift to metal.⁴ The Ghana Museums and Monuments Board acquired the buildings between 1960 and 1970, and they were declared a national monument in 1969.⁴

Guinea: Fouta Djallon

In the Fouta Djallon highlands of Guinea, Fulbe round houses and mosques carry large conical thatched roofs. The thatch is woven and layered over an inner shell, sometimes of bamboo, supported by columns and a central post; a mosque at Kébaly has a thatched roof that starts about 0.5 m (1.5 ft) above the ground and rises to about 12 m (40 ft).⁸ The cultural meaning of these houses and their roofs has been studied as a regional expression of Fulbe identity.¹²

Senegal: the Jola impluvium house

In the forested Casamance region of southern Senegal, the Jola (Diola) build the impluvium house, a ring of rooms with thick mud-brick walls arranged around a central court.¹⁴ Its thatched roof rises to a ridge and then falls both outward and inward, so that rain running down the inner slope pours through a central opening into a low-walled cistern used for drinking water.¹⁴ The thatch shades the walls from the sun, and evaporation from the cistern helps cool the air inside.¹⁴ Similar courtyard houses with inward-draining roofs are found among the Igbo, Yoruba and Edo of southern Nigeria.¹⁴

Roof types at a glance

Zone	Traditional roof	Structure	Main examples
Sahel and Sudanian savanna	Flat or gently domed earth roof with spouts	Palm or other timber, earth layers	Djenné (Mali), Tiébélé (Burkina Faso)213
Hausa lands	Earth vaults and domes	Cantilevered azara palm ribs, mud	Kano, Zaria (Nigeria)3
Atacora uplands	Earth tower-house with roof terrace	Earth, wood and straw	Koutammakou (Togo, Benin)5
Guinea highlands	Large conical thatch	Woven thatch on bamboo shell, central post	Fouta Djallon (Guinea)8
Casamance	Inward-draining thatched impluvium roof	Timber frame on mud walls	Jola houses (Senegal)14
Forest belt	Steep palm-frond thatch	Timber, bamboo, mud plaster	Asante buildings (Ghana)4
Whole region, modern	Corrugated metal sheet	Timber purlins, lower pitch	Replacements on traditional buildings45

Corrugated metal

Metal sheeting has displaced thatch and earth on a large scale. At the Asante shrines, lighter and lower-pitched corrugated iron replaced steep palm thatch on almost every building, and in the Koutammakou villages of Togo and Benin many newer houses have metal roofs as wood and straw become scarce.⁴⁵ Lower pitches are possible because metal sheets shed water without the depth of a thatch coat.⁴

Aluminium and coated steel in Nigeria

In Nigeria, aluminium roofing sheet is made locally and imported. The quality of thin sheet has been a long-running concern: in 2015, Nigerian manufacturers complained that imports of very thin aluminium sheets, around 0.2 mm, undercut local production, and discussed with the Standards Organisation of Nigeria (SON) a minimum aluminium gauge of 0.4 mm with no negative tolerance.⁹ SON has since seized large quantities of substandard roofing sheets in enforcement actions, including a consignment valued at ₦500 million in Imo State.¹⁰

Earth roofs revived: the Nubian vault

Since the late 1990s, the Nubian vault has been promoted in the Sahel as an alternative to imported metal and timber. The technique, derived from earth vaulting developed in Egypt, builds roofs of earth bricks and earth mortar without timber or formwork.⁷ The Burkinabé builder Séri Youlou and the French builder Thomas Granier built two prototype vaulted buildings at Boromo, Burkina Faso, in 1998, and the association La Voûte Nubienne was established in 2000.⁷

Foundations are 20–45 cm (8–18 in) deep and gable walls about 40 cm (16 in) thick; typical guidance limits vault width to about 3.2 m (10.5 ft) internally, with load-bearing walls about 60 cm (2 ft) thick and vault bricks about 24 × 12 × 4.5 cm (9.5 × 4.7 × 1.8 in).⁷ The roof is waterproofed with plastic sheeting laid over smooth mud mortar and protected by an enriched earth render at least 5–6 cm (2–2.4 in) thick.⁷ The programme has completed 8,500 buildings, including houses, schools and health centres, trained and certified 4,900 masons and reached about 108,000 beneficiaries in seven countries, saving an estimated 215,000 tonnes of CO₂ through local materials.⁶

Concrete

In heritage towns such as Djenné, cement and fired brick are increasingly replacing earth, a change that UNESCO counts among the threats to the old town's character.¹

Maintenance

• Earth roofs: replastering, ideally every year, and clearing of drainage spouts before the rains.²
• Hausa roofs: renewal of laso waterproofing about every five years.³
• Kassena roofs: replastering about every five years.¹³
• Nubian vaults: inspection of the earth render protecting the waterproof sheet.⁷

Heritage

Several West African sites recognised by UNESCO are defined in large part by their roofs and roofing crafts: the Old Towns of Djenné (1988), the Asante Traditional Buildings, and Koutammakou (2004).¹²⁴⁵