This thesis explores the role of barrier and threshold as a form of differentiation between objects and situations. Building elements such as façade, structure, and space become the means by which to distinguish between separate parts, functions, and experiences. Sited in downtown Washington D.C. the proposed office building becomes the permeable barrier between street and lawn. Within the building there is contrasting differentiation between service space and occupiable office space through the role of different building parts that make up an office building.