I encountered an issue with reinforcement installation on a construction site and there was a discussion regarding the following detail: In first drawing, the top reinforcement mesh is placed on top of the U bars, while in another drawing it is below the U bars, meaning the U bars hold both the top and bottom mesh. Is it critical how this detail is executed? Can the top mesh be placed on top of the U bars, or does it need to be under the U bars? Is it sufficient to ensure the proper overlap of bars only? The design standard being followed is Eurocode 2 (EC2).