A simple scheme for soil sampling and subsequent analysis for total soil phosphorus using perchloric acid digestion is described and its application illustrated by samples from the native farmstead of the Roman period at Cefn Graeanog in North Wales. The floor deposits of three distinctive buildings were analyzed, and the data obtained enhanced by Trend Surface Analysisto produce generalized maps of the phosphorus distribution, together with levels of significance of such distribution patterns. These were then used to clarify the details of the interpretation of the usage of the various types of buildings. Data for soil phosphorus concentration clearly reveal the pattern of erosion of constructed floors, the presence of features such as hearths and drains, and can be used to reveal patterns not otherwise discernible by excavation techniques. -- AATA