Large-scale brick-mortar structures and tough/strong nacre have common layered structure features. If enlarged by 20,000 times, fracture patterns in natural nacre consisting of micro-layered structures around 2 μm in thickness are virtually identical to those in large-scale brick walls. In this study, large brick-wall blocks about 3 m long and over 1 m tall were tested under three-point-bending and explained by a simple closed-form model. Two notch lengths (two and four brick heights) and two wall heights (about 1.1 and 0.6 m) were tested with 35 brick-mortar blocks. A linear relation between the maximum fracture load Pmax and the equivalent area Ae was established with the “structureal” tensile strength ft of brick walls as its slope, affirming one of the most common physical relations in Solid Mechanics, Pmax = ft × Ae. The equivalent area Ae contains all brick wall dimensions including the brick height Cch. As the characteristic structural measurement of brick wall elements, Cch plays a key role in modelling of the overall damage zone in front of the initial notch.