Many structures are designed to rest on mat foundations, however, due to construction difficulties associated with the existence of vulnerable neighborhood structures that may have shallow foundations, designers rely on using a set of closely spaced piles to stabilize the soil underneath the neighborhood structures. ln such case the mat may eventually be constructed over these piles, and its behavior may be influenced by their existence. The behavior of mat foundations supported totally on the soil and partially on an edge pile system has: been investigated, Different soil subgrade reactions are taken into account So as to, simulate soft, medium and hard soils. Moreover, different arrangements of piles as well as pile source€ Of resistance are taken into consideration' Common solutions proposed to. the problem by the designers are presented and evaluated. finally recommendations for dealing with such difficulties are driven.