A method for forming a foundation wall of a building structure having a building frame seated on the foundation, the method including coupling each of a plurality of elongated vertical members to a floor of the foundation and the building frame so that each of the vertical members extend between the floor and the building frame adjacent to an existing foundation wall, providing at least one elongated horizontal member through apertures of the vertical members such that the horizontal member extends between and passes through respective ones of the vertical members, coupling panels to the horizontal member so as to form, with the vertical members and the horizontal member an integrated self-supporting formwork which, with the existing foundation wall forms a cavity, having disposed therein, the vertical members and the horizontal member, and flowing concrete into the cavity so as to fill the cavity around the vertical members and horizontal member disposed within the cavity.