A building system for fabricating a multi-storey building structure, the system comprising at least one first building structure and at least one second building structure and means for elevating the second building structure to allow provision of the first building structure under the elevated building structure. A method for fabricating a multi-storey building structure, the method comprises the steps of providing a second building structure; elevating the second building structure; providing a first building structure under the elevated second building structure; and lowering the second building structure onto the first building structure. There is also provided the elevating means, such as jacks for elevating the building structure.