We manufacture our stair moulds from timber and 18m-birch plywood usually filled through the underside of the unit, although they can be made as cast depending on whether the soffit is to have a fair face finish, we have found that most winder or helical stair flight moulds are made in this way using a series of boards to form the risers and goings. On request, stair moulds can be cast on edge giving a fair face finish to both the soffit and the treads.