The study of matrix and total suction versus depth is important in the analysis and design of slabs on grade such as light structure building slabs and highway pavements. This paper quantifies the seasonal moisture profiles with depth in two typical expansive Oklahoma clays. These soils can be characterized as being medium to highly plastic, blocky structured, with a medium stiff consistency, shallow in depth and residual. Following a detailed field investigation and laboratory soil analysis, the project involves some variation in typical access tube installation technique and moisture monitoring with a capacitance probe. Adjustments to the access tube installation appear to work well. The paper presents characteristic curve equations for different soil horizons which are used along with the monitored moisture profiles to produce suction versus depth changes with time in the field. To date, some change in suction within the active zone has been recorded.