Geometric reasoning, the integration of geometric representation and inference in advanced computer systems, is presented as an issue at the forefront of research in construction automation. The unique demands that construction automation poses on such reasoning are discussed. An architecture that provides a structure for geometric reasoning is presented and results from a prototype implementation are shown. A project to develop geometric reasoning in the construction domain of panelized building systems is introduced. Within this project, two exemplary applications, structural/architectural design and construction sequence planning, each supported by the same geometric reasoning facility, are being demonstrated.