The knowledge base of design brief and process for office buildings appears relatively less developed than that for residential and other buildings of much smaller scales. The treatment of top management as the sole clients in office building design and space planning decisions is a misconception. This view has become obsolete with greater acceptance of broad-based industrial democracy. Despite this development, there is largely a dearth of objective information on the key issues underlying the effectiveness of facilities space management of commercial office buildings. Little effort has been invested in systematic development of comprehensive, coherent criteria to advance superior knowledge and direct decisions in policy and practice. A discovery of this shortcoming, among other gaps, motivated the author to research further into some influential factors in facilities space management of commercial office buildings, with the Sydney CBD as the primary study setting. As the dominant trend in the changing layout of offices is towards a more open-plan space, investigation of open-plan measures in the determination of facilities space management was considered imperative.