Using L-System to describe botanic 3D structures and grow plants by deriving its self-expandable grammar terms is a main stream of plant simulations. In addition, there are several pioneering projects aiming to adopt L-System to describe city and street structures. Because L-System is suitable for handling structural objects, in this paper, we propose to use a non-deterministic L-System for modeling a building’s composition including its floor layouts. The building can be a house that has similar rooms or even a very complex maze. By using L-system, we can semi-automatically create very flexible floor-layouts and interesting mazes based on different production rules.