A tie system and method for forming a wall from a hardenable pourable 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 a base tie and one or more wall ties, each of which directly attach to each other in a vertically stacked arrangement.