In view of declining populations and adequate housing provision in the western world, building in existing built contexts is becoming increasingly relevant. The conservation and use of existing buildings stock is not only ecologically sound but also an economic imperative. A prerequisite for computer-aided planning for existing buildings is both the use of on-site computer-aided surveying and the integration of all participants and disciplines in the planning process using integrated information and communication systems. The aim of this research project is twofold: to design a practice-relevant software concept for the support of the entire building surveying process embedded in the planning process, and to develop a practice-oriented mobile, digitally supported equipment and system environment for the digital architectural surveying of buildings. This paper will discuss the IT concept of a building surveying system, the software and hardware prototypes developed as well as usability aspects of wearable computers.