Title: Bafumbira
Content:  The Bafumbira built huts. The roofs were thatched with sorghum and grass from swamps. The walls were circular and were built with mud and sticks. Today they build brick houses with either iron sheet roofs or tiled roofs.
Title: Borcea
Content:  Many of the houses in Borcea are built using traditional means of construction and locally sourced materials. The masonry construction of the houses use sun-dried mudbricks called chirpici. Finer adobe is also used for exterior coating and as a binding material. The exterior of a house is usually covered with a layer of lime. Some houses are decorated with traditional motifs. The simple ridged roof consists of declined rafters that rest on vertical wall-plates on top of each wall. Tiles are often used as a roof covering although galvanised steel and bitumen could also be found. The roof often extends toward the front of a house to cover a small porch. Supporting frames are seldom used in this type of construction and are usually made of wood. Building an mudbrick house is a community effort with relatives of the house owner assisting in the erection of the building. 
Title: Architecture of Bermuda
Content:  air from the food. Kitchens were also distinctive, occasionally placed in out-buildings or in basements and noted for the use of wide, raised chimneys possibly inspired by the open hearth.  The earliest roofing was made of palmetto thatch but, partially from encouragement from the colonial government, stone shingles slowly came to be preferred. By 1687, only 29 of the 579 houses in Bermuda had been upgraded to stone and only 63 were shingled. The buildings were originally quite plain, due to the brittleness of limestone and lingering Puritanical asceticism. Only two means of decor have been observed in 17th century buildings: "Eyebrow 
Title: Buru
Content:  their field and return only for the religious service on Sunday. It was also rather common to move the entire village after some 20 years of exploiting a plot of land. Partly because of this, most settlements were rather small, with the smallest type accommodating one-two families (hum-hawa or hum-tapa), middle-type (hum-lolin) consisting of 3–10 houses and accommodating 20–50 people, and larger ones of 30–50 houses and 150–300 people (fen-lale). On the coast, there were several multi-ethnic settlements with more than 200 houses (ibu kota kecamatan). This local variety of terms for a "settlement" puzzled the Dutch colonizers trying to systematise the local registries. Traditional Buru houses were made from bamboo, often on stilts. The roofs were covered with palm leaves or 
Title: John Busst
Content:  Busst designed their new home to be strong enough to withstand cyclones, and utilised locally sourced materials. He employed a local builder to erect the shell of the building using bricks from the Silkwood Brickworks, and then used bamboo, an exotic that had been planted in the district in the nineteenth century, to create decorative ceiling features, architraves and fittings throughout the residence and to make furniture. Patricia Clare, who visited the Busst's new home at Bingil Bay in the 1960s, later wrote: "'The white house stood on its own cliff, the rainforest behind it, and in front the satin shine of blue water stretching away to where the reefs of lime lay hidden. It was the traditional Australian 
Title: Batak architecture
Content:  The roof of the Karo house is different from other Batak peoples, being a hip roof. The roof is the dominant feature of the house, sometimes being as tall as 15 metres high, against the supports and walls, both around 1.5 metres each. The most basic house, known as rumah beru-beru, has a basic hip and saddle roof. The rumah tersek has a double-storied roof with a saddle roof on top of the lower part. This improves ventilation in the house, reducing the impact of cooking smoke. A house with four gables, known as a si empat ayo has two saddle roofs crossed at right angles. In some cases an anjong-anjong, or miniature house, may be placed atop the house for further decoration
Title: Architecture of Bermuda
Content:  a stone gutter from the roof. Sunk six to eight feet down, they were typically rectangular and appeared barrel-vaulted above the surface. A distinctive style of developed, with a stepped profile of limestone slabs, grouted to make it impermeable and to stay clean. Rain on such a roof is slowed by the steps, rather than sloping tiles, and is collected by the gutter. This dependence on harvester rain led to a culture of water conservation, even with today's desalination plants. Interior wooden elements such as the ceiling and floors would be made of wood, often pine or hemlock from the continent.
Title: Architecture of Bermuda
Content:  These slates were slightly over an inch thick, and ten to twelve inches (305 mm) long; laid over a cedar frame in an overlapping pattern, they gave a down-stepped appearance. Finally, the roofs were coated with a mixture of lime, sand and water and, when available, turtle and whale oil to provide extra weather-proofing. Apart from the animal oil, this method of roof construction continues to be used. The walls, likewise, were often whitewashed, giving the island a faux snowcover if seen from a distance, though American author Mark Twain preferred to liken it to cake icing, "the white of marble...modest and retiring [in comparison]". 
Title: Rang Ghar
Content:  The roof of the Rang Ghar is shaped like an inverted royal Ahom long boat. The base of the monument has a series of arched entrances, while atop the roof sits a decorative pair of carved stone crocodiles. Many of the arched entrances have retained little more than their brick framework, with mere vestiges of sculptural adornments here and there. The Ahoms, who used special, thin, baked bricks, did not use cement but a paste of rice and eggs as mortar for their construction, a pulse called Maati Maah and a fish named Borali Mach in Assamese. They also made use of powdered mixed lime and bricks to cover the surface of the inner walls. It is 
Title: Zanzibar
Content:  of the 10th century Zanzibar was one of the central Swahili trading towns. Excavations at nearby Pemba Island, but especially at Shanga in the Lamu Archipelago, provide the clearest picture of architectural development. Houses were originally built with timber (circa 1050) and later in mud with coral walls (circa 1150). The houses were continually rebuilt with more permanent materials. By the 13th century, houses were built with stone, and bonded with mud, and the 14th century saw the use of lime to bond stone. Only the wealthier patricians would have had stone and lime built houses, the strength of the materials allowing for flat roofs, while 

Question: what material was used to build the roofs of houses in burzahom?
Answer: birch.