The use of masonry, and particularly of geo-sourced materials like compressed earth bricks, has been generating growing interest. These materials represent an alternative to cementitious products such as concrete, thereby reducing the demand for cement. For this substitution to be fully effective, improving their mechanical performance remains a crucial challenge. Although several studies have been conducted on the brick scale, the improvement of the masonry structure may be achieved through the improvement of mortar joints and their interface with the brick. One of the best ways to ensure perfect adhesion of interfaces is to produce full bricks with cavities such that the wet mortar takes the shape of the cavity and anchors itself in the brick as it hardens. Such cavities can influence the global behaviour of masonry. The common shape of the cavity in the CEB is trapezoidal and is located only at the middle top of the brick. This study aims to investigate the real added value of these cavities and to study the influence of the different shapes and sizes of the cavities on masonry behaviour. To achieve this objective, an experimental study and numerical simulations were conducted. In the first approach, a push-out test was performed on triplets formed using bricks without cavities. This first approach allowed to obtain interface parameters such as cohesion and coefficient of friction. The same test was performed numerically using triplets formed by bricks with different cavities. In this second approach, a total of 12 bricks were designed with different shapes and sizes of cavities. The results showed different distributions of stress at the interface with a concentration near the joint protrusions.