Xisi Bei district is one of the 25 hutong protected zones in Central Beijing and as such is subjected to this development pressure that is leading its “siheyuan” typology into extinction with the traditional urban life being reduced and in certain cases eliminated. The project proposal attempts to use this traditional system of urban organization as a basis and starting point for the reinterpretation and growth of Xisi Bei area. This is achieved through building a catalogue of a generative typology of four- combine- gardens upon the concept of probability, consequently breeding a wide domain of modular arrangement onto the block of Xisi Bei.