This paper describes and develops a preliminary approach to the measurement of the information content of two-dimensional design drawings. We utilise a general method for extracting information from an encoded string of symbols as a canonical representation of architectural plans. The information content of each drawing or set of drawings is determined by measuring its entropy. We present two classes of qualitative representation of shape and space. The first uses a qualitative representation of the outline of shapes in the drawing. The second uses a qualitative representation of the spaces described in the drawing. We describe the preliminary implementation of the method to a time-evolution of two formally described design styles, Romanesque and Gothic cathedral plans.