The mechanical behavior of non-bonded unturned shear walls (UPT) of high resistance SI ELiment masonry with thin layer mortar (CASIEL-TLM masonry) was experimentally and numerically investigated. Eight walls were tested with the following key variables: unit type, prestressing level and cross-sectional shape (rectangular or T-shaped with interlocking of the web and flange). A wide measurement scheme was adopted that allowed the derivation of the curvatures and mean strains in the inferior region of the wall, besides the displacements of the wall. Since UPT masonry is characterized by the absence of local compatibility between masonry tendons and UPT, a numerical model was developed for monotonous quasi-static analysis that provides an iterative solution for the global interaction between masonry tendons and UPT. In the numerical model a stress-strain diagram of common masonry was adopted. A peculiarity of CASIEL-TLM masonry is the kicker course, which reduces the rigidity of the lower region of the shear wall. This layer was modeled with non-stresses, linear-elastic behavior and reduced stiffness. However, the model underestimates the experimental deformations of the rectangular cutting walls, while the resistance is in reasonable agreement. The walls with T-shaped cross-section failed prematurely by shearing of the web bead interface, resulting in diagonal dividing cracks in the locking units. This paper deals with the experimental results of the UPT CASIEL-TLM masonry cutter walls with rectangular and T-shaped cross-sections and with the numerical modeling of UPT's shear overturning behavior with rectangular cross-section.