This work aims at investigating the behaviour of load-bearing masonry wall joined with thin-adhesive mortar when exposed to fire, with both theoretical and experimental analysis. This analysis is addressing the need for understanding and improving the fire performance of walls. For this purpose, the fire response of the studied wall is first investigated on the basis of experimental data, including temperature evolution inside clay masonry units. Three-dimensional finite element simulations are then carried out using several values measured at various temperatures on clay samples extracted from masonry units: tensile strength by bending, compressive strength and Young's modulus as input parameters. This modelling allows to estimate the distribution and the evolution of thermal gradient and mechanical stresses inside webs and shells of the clay masonry units. The shell may fail either by being crushed under compression, or by the detachment of its partitions under traction. Experimentally measured strengths on partitions at high temperature are compared to simulated compressive and tensile stresses. These comparisons are used for the identification of both the shell failure mode and the failure time.