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 (c. 1050) and later in mud with coral walls (c. 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 the majority of the population lived in single-story thatched houses similar to those from the 11th and 12th centuries. According to Tom Middleton and Mark Horton, the architectural style of these stone houses have no Arab or Persian elements, and should be viewed as an entirely indigenous development of local vernacular architecture. While much of Zanzibar Town's architecture was rebuilt during Omani rule, nearby sites elucidate the general development of Swahili, and Zanzibari, architecture before the 15th century.