ABSTRACT
Plans, sections and elevations have a level of precision in terms of the eventual building which is difficult to produce as far as materials are concerned: when I draw a straight line on plan and a vertical line on section I know this denotes a straight wall which is not inclined; if I draw a curved line I know this would be built as a curved wall. The line, drawn while I am designing, tells me nothing, however, whether the wall is in brick or stone or concrete. Large scale construction drawings can distinguish between these materials by conventional hatching but there are no means of doing so at the early design stage although the difference between materials is then also important.
