Spatial engineering is an activity of fundamental importance when designing large, complex, made-to-order engineering products. Work is described which is concerned with the application of a simulated annealing optimization method and knowledge-based systems techniques to concept design stage spatial engineering problems. The discussion begins with a description of a prototype environment for computer-aided design tools that are able to manipulate and analyze a product's topology, rather than its precise geometry. The content then focuses on on-going enhancements and refinements that are being made to the prototype environment to improve its efficiency and range of application. An example is presented demonstrating the use of the system in defining a conceptual layout of the fuselage for a military aircraft.