The design of reinforced concrete flat slabs can be governed at failure by punching shear close to concentrated loads or columns. Geometrical features, reinforcement layouts and in-plane forces provided by external vertical elements, such as shear walls, can affect the membrane action and, consequently, the punching shear resistance. This paper presents a study on reinforced concrete continuous flat slab whose lateral expansion is restrained by the presence of vertical elements considering also shrinkage effects.