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The plastic voided slab system in a building are seems effective and efficient in terms of economy, environmental sustainability as well as structural performances. Buildings with the plastic voided slab system are able to decrease the amount of concrete by 30 percent or more. It reduces the concrete from the mid height of slab where the concrete has no significant structural function. This paper presents, a building having two way reinforced concrete slab with the plastic voids construction in comparison with a building with the traditional solid flat slab construction under the same load carrying capacity. Stepped back building are taken for both the cases with common span of 7.5m in each direction and having column size 800mmx800mm for a building with the 310mm thick solid flat slab and column size 725mmx725mm for a building with the 230mm thick plastic voided slab consisting 180mm diameter spherical plastic balls. The solid flat slab design process follows the IS 456:2000 Code of practice for plain and reinforced concrete, direct design method. While the plastic voided slab design process is adapted from the bubble deck guide for compliance with the Indian standard. Results of comparison study are presented