This paper discusses the development of a machine-readable language representing the principles of building design. Building design is a complex process taking into account many different factors and variables, such as the function, site context, environment, materials, cost, culture, etc. The focus of this work is to develop an ontology describing the principles for building design and relationships among them. The methodology for the creation of an architectural ontology is discussed, as well as the tools used to construct and link concepts, attributes, and relations. The architectural ontology could be used in software applications for automated design, where design parameters are prescribed. In that sense, information about the site, physical systems, building orientation, materials and other constraints can be prescribed the by the user. This paper discusses the applications of an ontology for tall building design, since tall structures impose special problems due to the scale and complexity.