Studies of software engineering projects show that a large number of usability related change requests are made after its deployment. Fixing usability problems during the later stages of development often proves to be costly, since many of the necessary changes require changes to the system that cannot be easily accommodated by its software architecture. These high costs prevent developers from meeting all the usability requirements, resulting in systems with less than optimal usability. The successful development of a usable software system therefore must include creating a software architecture that supports the right level of usability. Unfortunately, no documented evidence exists of architecture level assessment techniques focusing on usability. To support software architects in creating a software architecture that supports usability, we present a scenario based assessment technique that has been successfully applied in several cases. Explicit evaluation of usability during architectural design may reduce the risk of building a system that fails to meet its usability requirements and may prevent high costs incurring adaptive maintenance activities once the system has been implemented.