Architectural design relies on 3D modeling procedures, generally carried out in Building Information Modeling (BIM) formats. In this setting, architects and designers collaborate on building designs, iterating over many possible versions until a final design is agreed upon. However, this iteration is complicated by the fact that any changes need to be made by manually introducing changes to the complex BIM files, which lengthens the design process and makes it difficult to quickly prototype changes. To speed up prototyping, we propose VR-Arch, a virtual assistant that allows users to interact with the BIM file in a virtual reality (VR) environment. This framework enables users to 1) make changes directly in the VR environment, 2) make complex queries about the BIM, and 3) combine these to perform more complex actions. All of this is done via voice commands and processed through a ReAct-based agentic system that selects appropriate tools depending on the query context.This multi-tool approach enables real-time, contextualized interaction through natural language, allowing for a faster and more natural prototyping experience.