Walls: the minimum area of horizontal reinforcement As,hmin
Eurocode 2 part 1-1: Design of concrete structures 9.6.3 (1)
Horizontal reinforcement running parallel to the faces of the wall (and to the free edges) should be provided at each surface. It should not be less than As,hmin.
The recommended value for the minimum area of horizontal reinforcement As,hmin is either 25% of the vertical reinfocement or 0,001Ac whichever is greater.