Abstract: An accommodation unit to form, with a plurality of such units, a building, comprises a housing having corner posts, sidewalls, floor and ceiling panels, a window unit at one end and an end wall with a doorway at the other end. The housings are intended to be located side-by-side and stacked one on top of the other secured together at the corner posts.Concrete is cast between the adjacent side walls of the housings and the outer faces of the side walls are formed with T-section ribs which key with the concrete to provide a composite rigid wall.