One-way ribbed slabs are adopted regularly in construction where the ribs transfer the loads in one direction to the supporting beams. When spans are larger than 5 meters a transverse rib is recommended. This numerical analysis research aims to study the effect of the transverse rib on the carrying capacity of a central rib under a direct uniformly distributed wall load. The ribbed slab was modelled on SAP2000 structural analysis program and numerical results were compared, where two cases were considered: a reference ribbed slab (without a transverse rib), and a ribbed slab with a transverse rib. Results of the slab without a transverse rib revealed that the main rib carrying the uniformly distributed wall load fails much earlier where large stresses and strains developed revealing large deflections, since all the load is carried by that single main rib alone. On the other hand, for the slab with a transverse rib, failure occurs much later at higher levels of loads where stresses and strains develop slowly and deflection is much less, since the adjacent ribs assist the main rib in carrying the uniformly distributed wall load hence prolonging the time to failure. In conclusion the transverse rib of high importance, where it ties main ribs together allowing them to work collectively in carrying load that may coincide on one of the main ribs.