Description: In modern architecture, construction processes are based on top down planning, yet in vernacular architecture but also in nature, the shape of shelters/nests is the result of evolutionary material processes which takes place without any global coordination or plan. This work presents a framework for exploring how self-organizing structures can be achieved in a bottom up fashion by implementing a swarm of simple robots(bristle bots). The robots are used as a hardware platform and operate in a modular 2D arena filled with differently shaped passive building blocks. The robots push around blocks and their behavior can be programmed mechanically by changing the geometry of their body. Through physical experimentation and video analysis the relationships between the properties of the emergent patterns (size, temporal stability) and the geometry of the robot/parts are studied. This work couples a set of agent based design tools with a robust robotic system and a set of analysis tools for generating and actualizing emergent 2D structures.