a bearing wall and slab system is used mainly in low-rise residential type buildings.salbs are generally 100 mm to 200 mm thick with spans from 3 m to 7.5 m.when the slab is supported only on opposite sides,the slab bends in one direction only and the slab is called a one-way slab.the entire load is transmitted one way to the two supports.a very similar situation exists in a long rectangular slab (length about twice greater than the width)supported on all four sides.the bending of the slab is predominantly along the short span and most of the load is transmitted across the short span onto the two longer supports. when the slab dimensions approach a square the bending action along both spans becomes relatively significant.in this case,load is transmitted in both directions and the slab is termed a two-way slab.