The nominal buffer layer combination is evaluated in this paper to control swell and improve the strength property of expansive soils by using geomembrane (G) and various buffer layer materials such as river sand (RS), pond ash (PA) and murram (M). Different combinations of buffer layer, percentage of stabilizing agents (lime, L, and cement, C), and conditions (cured (C) and uncured (UC)) were used to conduct tests. The expansion ratio (ER) was found to be not significantly reduced in combinations with untreated buffer layers when compared to treated buffer layers. ER was further reduced in combinations with geomembrane, demonstrating that geomembrane prevented water movement and prevented Black Cotton (BC) soil from becoming saturated. Three criteria were used to assess the optimal combination: reduction in swell, gain in strength, and feasibility. BC + G + BC3%L + RS (C) and BC + G + M6%L + PA (C) both fit the requirements for construction on expansive soils.