Roofing in Tanzania

Tanzania combines a long Indian Ocean coast and the islands of Zanzibar with a high, largely dry interior plateau, the Rift Valley lakes and the mountains of the north. Its roofing history is unusually deep on the coast, where Swahili builders were roofing mosques with coral-stone vaults and domes in the 13th and 14th centuries, while inland houses used grass, leaves, earth and dung. By the 2022 census, about 85% of households lived under iron-sheet roofs.

Climate and hazards

The coast and islands are hot and humid with two rainy seasons; the central plateau is semi-arid with a single rainy season; the highlands are cooler and wetter. Roofs must deal with tropical downpours and strong sun everywhere, salt air and high humidity on the coast, and termites and fire risk for organic materials. Earthquakes also occur in the Rift system: according to one published account, an earthquake in 1331 brought down much of the Great Mosque of Kilwa.

Roofing history

The medieval coast. At Kilwa Kisiwani, the Great Mosque probably originated in the 10th century; its northern prayer hall, built in the 12th century, was fully roofed on coral-stone and later timber pillars. Between 1294 and 1302 a southern extension was added to carry a semicircular vault, and in the early 14th century Sultan al-Hasan ibn Sulaiman added a large dome, reportedly the only one left standing after that earthquake. Builders used coral stone for walls and columns, lime plaster for floors and lime mortar on later walls. Kilwa Kisiwani and the nearby town of Songo Mnara (occupied from the 14th to 16th centuries) were inscribed together as a UNESCO World Heritage Site in 1981.

Zanzibar. In Zanzibar, multi-storey stone buildings were made of coral rag and lime with mangrove poles and coconut palm material. Most of the architecture of Stone Town dates from the 19th century trade boom, when Omani, Indian and Persian merchant communities settled there.

The interior. Inland, documented early buildings are few. The house at Kwihara near Tabora known as Tembe la Livingstone, built in 1857 of stone and mud in a coastal Swahili style, was used by David Livingstone and Henry Morton Stanley in 1871-72 and is now a national historic site.

Modern era. Corrugated iron spread during the German and British colonial periods and after independence. At the 2022 census, 85.6% of households lived in houses with improved roofing materials.

Traditional and vernacular roofs

• Coral-stone roofs on the coast and Zanzibar: coral and lime laid over mangrove-pole joists (see Swahili coral-stone house).
• Makuti: sun-dried coconut palm-leaf thatch, widely used along the coast and on Zanzibar.
• Maasai house in the north: low domed dwellings packed with leaves and plastered with cattle dung (see Maasai enkaji).
• Hadza shelters: domed huts of branches that are thickly thatched in the cooler season.
• Barabaig huts: some built with flat-roof frames inside thornbush enclosures.

Roofing today

The 2022 Population and Housing Census gives the main roofing material of households:

Main roofing material	Tanzania	Mainland	Zanzibar
Iron sheets	84.8%	84.6%	92.5%
Grass/leaves	11.6%	11.7%	5.7%
Mud and leaves	2.4%	2.5%	0.2%
Others	1.2%	1.1%	1.6%

Taken together, organic and earth roofs (grass, leaves and mud) still covered about one household in seven nationally, but only about one in seventeen on Zanzibar.

Codes, standards and regulation

In Zanzibar's Stone Town, alterations to historic buildings are governed by the Stone Town Conservation and Development Act of 1994.

Industry

Regional coated-steel groups, including Safal Group (parent of Kenya's Mabati Rolling Mills), list Tanzania among their operating countries.

Notable roofs

• Great Mosque of Kilwa (Kilwa Kisiwani, UNESCO 1981): coral-stone vaults and a 14th-century dome.
• Stone Town of Zanzibar (UNESCO 2000): about 1,709 coral-stone buildings, many in poor repair, with large verandas behind carved wooden balustrades.
• Tembe la Livingstone, Kwihara: 19th-century stone-and-mud house, now a museum.

Local roofing terms

• mabati (Swahili): metal roofing sheets.
• makuti (Swahili): coconut palm-leaf thatch.
• tembe (Swahili): used in the name of the Kwihara house, Tembe la Livingstone.

Sources and gaps

The census brief does not define its "mud and leaves" category or break down "others". The traditional flat earth-roofed tembe house of central Tanzania, often described in older literature: published information is limited. Tanzanian national building regulations and roofing standards were not identified.