A tie system and method for forming a wall from a hardenable building material. In one embodiment, the tie system includes multiple ties configured to be directly interconnected into a vertically extending tie stack such that multiple tie stacks can be positioned over a footing in a spaced apart arrangement. The multiple tie stacks are configured to extend substantially perpendicular between substantially parallel panel structures. Each tie stack includes one or more base members and one or more wall ties, each of which directly attach to each other in a vertically stacked arrangement.