The current trend of indiscriminate dumping of plastic wastes has lead researchers to look into the reuse of these materials especially in the building industry. In this work, waste plastic bottles polyethylene terephthalate (PET) were recycled to 4 mm diameter polymer rod and were used to replace wire mesh in the topping of waffle slab. The flexural strength and deformation of 12 waffle slabs with sizes of 700 mm × 700 mm × 120 mm, and 800 mm × 800 mm × 120 mm were determined with three samples for each size. The topping of six slabs were reinforced with the polymer rod while the remaining six were reinforced with wire mesh which served as the control. The laboratory test carried out showed that the young modulus of elasticity for polymer rod and wire mesh was 12,766 N/mm2 and 30,469 N/mm2 respectively. The average crack width for the waffle slabs reinforced with polymer rods and wire mesh range from 1 mm to 2.3 mm having maximum deflection of 42.93 mm and 40.64 mm respectively. The average ultimate flexural load was 50KN for both samples. The study concluded that the polymer rod could be used as topping in waffle slab.