Abstract: A concrete contraction and expansion joint with a mechanism providing adjustable height, enabling fast, efficient pouring of concrete over layout surfaces, achieving accurate thickness and desired slope of the concrete slab. In a preferred embodiment, the concrete section joint assembly (35) is pre-formed by using longitudinal sections having a channel (37) for holding elastomeric material (42), with the section supported from its underside by shaped support units, each mounted on two threaded studs (24). A specially designed nut (28) threaded on each stud (24) provides height adjustability and by rotation raises or lowers the height of support unit sides. The height adjustment, provided from above the assembly, can be performed before concrete pouring is completed and an upper edge portion of the elastomeric material or the upper edges of the channel are visible with the concrete surface, providing a reference height and slope for the concrete surface.