Comfort and habitability are requirements for housing quality, affected by underfloor system. Thus, this study aims to design lightweight concrete slabs underfloor with the use of ethylene vinyl acetate (EVA) aggregates, with two grain sizes of conventional aggregates replaced with EVA. The experimental counted on four unit mixes, varying the ratio between EVA coarse and fine aggregates and natural aggregates. The underfloor plates were molded with thickness of 3, 5 and 7 centimeters, and 3cm plus 1cm of conventional coating. Slabs were submitted to specific mass and standardized impact sound pressure level tests. Results showed a correlation between specific masses and impact sound values, being that 7cm thickness slabs with smaller specific mass, with total aggregate replacement, presented noise intensity reductions of 17dB in comparison to same thickness slabs with natural sand and smaller content of EVA coarse aggregate; and a 28dB reduction in relation to the slab without underfloor.