An inherent weakness of masonry structures is low bond and bond strength. Although masonry bond is a result of many interrelated factors (e.g. surface texture, surface absorption and mortar composition, etc.), surface absorption of masonry units has a significant effect on masonry bond. Following a critical review of the current measurements of the surface absorption of masonry units, the theoretical bases of sorptivity as a measurement of surface absorption are presented. The limitations of sorptivity measurement are discussed through a review of the application of the concept of sorptivity to different porous building materials. An experimental programme to examine the surface absorption of masonry units is described. Analysis of the results showed sorptivity to be a simple and reliable measurement of surface absorption for masonry units that could be used in building standards.