Abstract: A building system comprises building module 16 24 in the shape of a truncated tetrahedron wherefrom a building can be constructed on a horizontal surface 18 by making horizontal tessellations of a first form 16 of module where the module 16 sits on a hexagonal faces and a second form 24 of module where the module 24 sits upon a triangular face, tessellation being achieved when a hexagonal panel 20 of a first form 16 of module is abutted against a hexagonal panel 20 of a second form of module. Multi-storey buildings can be constructed using the upper surfaces created from contiguaus topmost panels 26 28 being employed as the horizontal surface 18 26 28 for construction of an upper storey tessellation. Alignment of upper 26 28 and tower like panels between the upper surfaces of one storey and the tower surfaces of the next higher storey permits automatic creation of utility ducts 30 within the multi storey building.