The following recommendations apply to houses of one or two storeys and two-storey flatted dwellings in which each flat has its own separate access from the outside ground level. Each house or flat is assumed to be intended for use by one family exclusively for residental purposes and to have a total floor area not exceeding 1,500 sq. ft. per house and 1,000 sq. ft. per flat. Houses and flats with a basement or roof space which is used as habitable accomodation are not within the scope of the recommendations in this Chapter but will be covered in the full Chapter for all classes of buildings.