Virtual Architecture is a virtual place that uses the metaphor of architecture and provides an online environment for various human activities. While Virtual Architecture inherits many of the characteristics of physical architecture, it is possible to reconsider the virtual in terms of flexibility and autonomy. This paper presents a Usercentred Virtual Architecture (UcVA) Agent, a kind of rational agent capable of representing a person in virtual worlds and designing virtual worlds based on current needs. The UcVA agent model has a design component that uses the shape grammar formalism. This model and a sample grammar are demonstrated for a meeting room scenario.