In this paper, the architectural design is considered regarding the lines drawn and the words written from where they come. These written traces of the project, that appear in its duality, condense a though that belongs exclusively to architecture and its design. The study of the signs in this double writing of architectural design allows an access to this specific thinking. Instead of the dialectic between the iconic and the verbal, this approach to the architectural project considers the signs of double writing systematically as a significance unit whose interpretation is found in something outside the logos; it is in the place of the architectural work. The concept of sign of Charles S. Peirce, while three-dimensional between three factors, allows us to assign to the signs of the double writing an interpretation.