A housing (1) for mounting in the ground to provide an access manhole or the like has a pair of spaced-apart sides (2) interconnected by ends (3) to define a rectangular open-topped chamber (4). Each of the sides (2) has a twin wall construction with an inner wall (6) and an outer wall (7) which are spaced-apart and interconnected by ribs (9) arranged in a zig-zag formation between the inner wall (6) and the outer wall (7). The outer wall (7) is convex to resist bending of the sides (2) under side loading of the housing (1) when in use mounted in a carriageway or the like due to traffic passing overhead. <IMAGE>
