An incident blast wave interacting with a building will diffract around the side walls and roof, resulting in reduced blast loads on the back wall. There is also a region behind the back wall where the blast loads will be attenuated (i.e., lower than the incident blast loads). This paper focuses on defining the attenuated blast load region as a function of the blast wave strength and building dimensions. Characteristic parameters are utilized to present the analysis results, including wave length, wave length normalized by a characteristic building dimension, and normalized standoff distance from the building back wall. Blast load adjustment factors (i.e., ratio of the diffracted to incident blast load) are used to define the blast load attenuation as a function of these characteristic parameters. The purpose of this work was to generate a database of the shock attenuation behind a structure for engineering modeling applications.