Architectural drawings are made according to a set of conventions, which include particular views (floor plan, section etc.), sheet sizes, units of measurement and scales, annotation and cross referencing. Conventionally, drawings were made in ink on paper or a similar material, and any copies required had to be laboriously made by hand. The twentieth century saw a shift to drawing on tracing paper, so that mechanical copies could be run off efficiently.
The development of the computer had a major impact on the methods used to design and create technical drawings, making manual drawing almost obsolete, and opening up new possibilities of form using organic shapes and complex geometry. Today the vast majority of drawings are created using CAD software.
The size of drawings reflects the materials available and the size that is convenient to transport – rolled up or folded, laid out on a table, or pinned up on a wall. The draughting process may impose limitations on the size that is realistically workable. Sizes are determined by a consistent paper size system, according to local usage. Normally the largest paper size used in modern architectural practice is ISO A0 (841 mm × 1,189 mm or 33.1 in × 46.8 in) or in the USA Arch E (762 mm × 1,067 mm or 30 in × 42 in) or Large E size (915 mm × 1,220 mm or 36 in × 48 in).
Architectural drawings are drawn to scale, so that relative sizes are correctly represented. The scale is chosen both to ensure the whole building will fit on the chosen sheet size, and to show the required amount of detail. At the scale of one eighth of an inch to one foot (1:96) or the metric equivalent 1 to 100, walls are typically shown as simple outlines corresponding to the overall thickness. At a larger scale, half an inch to one foot (1:24) or the nearest common metric equivalent 1 to 20, the layers of different materials that make up the wall construction are shown. Construction details are drawn to a larger scale, in some cases full size (1 to 1 scale).
Scale drawings enable dimensions to be "read" off the drawing, i.e. measured directly. Imperial scales (feet and inches) are equally readable using an ordinary ruler. On a one-eighth inch to one foot scale drawing, the one-eighth divisions on the ruler can be read off as feet. Architects normally use a scale ruler with different scales marked on each edge. A third method, used by builders in estimating, is to measure directly off the drawing and multiply by the scale factor.