The manual creation of virtual environments is a demanding and costly task. With the increasing demand for more complex models in different areas, such as the design of virtual cities, video games and computer animated movies, the need to generate them automatically has become more necessary than ever. This paper presents a method for the automatic generation of traversable houses, using architectural rules and an L-System to generate the rooms. The method has some innovating features, including the implementation of rules coded in a grammar, to produce 2D floor plans as well as complete 3D models with a high level of detail, in just a few seconds. The generation grammar was tested with legal rules from RGEU (Regulamento Geral das Edificações Urbanas) for Portuguese modern houses as well as heritage rules referring to the Roman civilization. A framework was also developed, and two different applications to evaluate it, which allow for the generation of multiple houses and interactive navigation.