INTRODUCTION
The creation of an indigenous architecture in southern Africa has always been part of a larger process whereby both the individual dwelling unit and the larger homestead or village derive their existence from the found and natural materials of the physical environment. They use their immediate surrounds as a ready quarry for the timber, the stones, the clay and the grass required for their construction.
Theirs therefore is a highly functional kind of architecture which uses materials according to their natural properties. As a result the form of dwellings, the size of settlements and even the resolution of certain structural details, such as the roof apex, have all been subjected to different environmental forces leading to certain regions developing strong architectural identities in their own right. In spite of these outward differences however, all rural architecture is linked by the fact that this habitat is part of a delicate environmental balance which brings together human settlement, economic activity, physical environment and culture into one larger interacting whole. Thus if one of vernacular architecture's attractions lies in its seeming ability to merge with immediate surrounds, that is because it draws upon its social and physical environs for its very being.
THE ECOLOGY OF THE DWELLING UNIT
Traditionally the dwellings of rural southern Africa have been built predominantly out of saplings, timber, clay, grass and cow dung. Depending on the region, stone rubble and shales have also been used in wall construction while natural lime has been found to be a good soil stabiliser. However, being natural materials, these have also tended to provide a home to a variety of insects, lizards and other small fauna which can subsist alongside, or even in spite of, man. This has led to the rural dwelling developing an internal ecological balance of its own, with man and his activities on the one hand, providing a check to the infestation of his environment on the other. Thus it was found, during the course of current research, that when rural residents built fires in their dwellings for both heating and cooking, their smoke rose and percolated through the thatch grass roof thus effectively fumigating it and discouraging vermin infestation.
To a certain extent this process must also be assumed to be effective where clay walls are concerned. Therefore, should a family decide, for any reason, to change their grass roof and replace it with zinc sheeting, they will no longer be able to build an effective fire within it without the assistance of a smoke flue. As in the majority of cases the flue has not found popular application in the region's architecture, it is likely that this group would soon cease to build internal fires in their dwelling thus terminating the fumigating process. One probable result of this action will be that they will need to introduce cement and brick into the structure in order to reduce or eliminate infestation of the walls. Once a family initiates the use of cement, it is also likely to cut down on its maintenance efforts by using this material in the floor. However cement floors are hard and cold to sleep on and therefore European- style furniture will have to be bought to replace traditional grass sleeping mats. By implication then, such a family will be making a transition from a local subsistence and craft- manufacturing economy to an externally based cash-using society. However, in view of the fact that industrially manufactured furniture is normally based upon a 90°geometry and that circular floor plans are thus difficult to furnish, a change in fittings might also bring about a change in the dwelling's floor plan from the circular to the square, thus also forcing a change in its roof technology.