This paper will introduce a new method, known as small graph matching, anddemonstrate how it may be used to determine the genotype signature of a sample ofbuildings. First, the origins of the method and its relationship to other ?similarity? testingtechniques will be discussed. Then the range of possible actions and transformations willbe established through the creation of a set of rules. Next, in order to fully explain thismethod, a technique of normalizing the similarity measure is presented in order to permitthe comparison of graphs of differing magnitude. The last stage of this method ispresented, this being the comparison of all possible graph-pairs within a given sampleand the mean-distance calculated for all individual graphs. This results in theidentification of a genotype signature. Finally, this paper presents an empiricalapplication of this method and shows how effective it is, not only for the identification ofa building genotype, but also for assessing the homogeneity of a sample or sub-samples.