Yoruba houses, like those of the various cultural groups in tropical Africa, are generally thought to be a mere place of abode and shelter from the tropical downpour and the sun. This is a physical environmental view which underestimates the importance of the socio-cultural values of the Yoruba in house formation. The Yoruba household is considered in this paper to be a structured, socio-cultural institution which has three important components. The overriding influence of the lineage ancestor on the household makes up the first component, and this is considered to be the spiritual foundation of the institution. The head of the lineage forms a link between the ancestor and the living members. He ensures maximum cohesion among the extended family members through the exercise of his legislative, judicial and administrative powers. The roles of the lineage head constitute the second component of the institution, i.e., the administrative component. The complex socio-economic interactions among the members of the extended family make up the third component. These three main components jointly determine the siting of Yoruba houses, the various building and space-formation elements of the house, the processes of construction and the materials used for building. Thus socio-cultural factors, as opposed to physical environmental ones, are considered to be the primary forces that create Yoruba house forms.