Expanding soil, sometimes known as shrink-swell soil, can cause significant volume changes—up to thirty percent or more, depending on the soil moisture content—which can lead to foundation issues. This soil type can result in building settlement during decreasing moisture periods, exerting lateral pressure on foundations, basements, or retaining walls. There are several ways to address this problem; the most common one is to use stabilizing substances like cement or lime. The purpose of this study is to add fly ash and lime to expanding soil to increase its stability. First, bentonite is mixed with different weight percentages of fly ash (20, 35, and 50%). The mixture is subsequently modified by adjusting lime percentages (3, 5, and 8%). The test specimens undergo several examinations, including grain size distribution, Atterberg's limit test, free swell tests, and standard Proctor tests. If calcium or magnesium ions are substituted for sodium or potassium ions, the clay's plasticity index is greatly reduced, which lowers the bentonite soil's capacity to swell. When 20% fly ash and 8% lime are added to bentonite, the swelling index significantly decreases and approaches the values attained when 3% lime and 35% fly ash are added. The results indicate that lime and fly ash together can stabilize expansive soil and produce better soil qualities that are appropriate for building. The study shows that expanding soil can be efficiently stabilized by adding lime and fly ash to the composition. Stabilization with these agents turns out to be a workable therapy, enhancing the qualities of the soil for building. Results from laboratory research show that lime and fly ash stabilize expansive soil, which is useful information for engineering applications.