Reliability of masonry walls under wind effects:: Importance of the joints and error models in design

French design and calculation rules concerning masonry walls are based on the principle of admissible stresses verification. This approach does not incorporate explicitly neither the idea of partial factors nor the idea of loads combination. It is, then, not possible to take into account, in a detailed way, the influence of uncertainties that may affect the parameters involved in the design and calculation. In the present paper, a wall of masonry is analyzed, under lateral wind loads and vertical loads, the whole being considered as random variables, in order to evaluate the mechanical influence of the joints quality two kinds of walls are considered : walls with both horizontal and vertical joints, in one hand, and only with horizontal joints, in the other hand. The mechanical properties of the joints, considered as random variables, are those of the mortar : its strength, its cohesion and mortar-brick friction factor. The limit state concerns the transformation of the wall into a mechanism due to joints failure while the bricks are assumed to remain as rigid and solids. The use of the mechanical models, described herein, aims to construct more economically while avoiding wall oversizing. Aiming to provide useful bases for assessing partial factors applicable to such structures, a reliability-oriented analysis has been performed and demonstrates the effect of the parameters variability.