Vernacular Architecture is 'architecture without architects'. The term vernacular has been used interchangeably with the terms folk, common, native or non-academic architecture. Definitions often refer to its localised nature, use of traditional skills, use of locally produced building materials and absence of architects. All these points are debatable!
Another definintion is on functional grounds: contrasting "high-style building types as houses, churches, state houses, and theaters" with "utilitarian and vernacular building types ranging from factories and bridges to barns and gas stations".
Kingston Heath argues that a locality with a unique character, culture, materials, climate, topography and so on can "filter" conventional ideas about architecture (vernacular architecture or otherwise). The result is the "product of a place, of a people, by a people."
All prehistoric architecture is vernacular, by most definitions, but 'vernacular architecture' tends to be seen as historic buildings.
There is, at the moment, an ongoing debate on the limits of vernacular architecture. Earlier, rural, pre-industrial buildings were the focus. Urban vernacular, industrial vernacular, and the use of vernacular idiom by architects are now all being considered.