A stair assembly comprising at least two stair modules with each connected to an adjacent module; the stair assembly comprising a first module having first and second side abutments and spanning therebetween a stair tread. There is at least one other abutment surface associated with said first and second side abutments and which provides a bearing surface to receive and retain an adjacent stair module. The second module includes a stair tread which when disposed adjacent the first module is disposed in an us elevated position relative to the stair tread of the first module, wherein the first and second stair module are interconnected via an auxiliary module.