A filter plate subframe for a filter plate frame assembly having a filter plate frame and a filter plate subframe receivable therein, characterized in that the subframe comprises separate periphery segments (2a, 3a, 4a, 5a, 6a) attached to each other so as to form a continuous periphery region of the subframe, such that the periphery region surrounds and delimits an open region of the subframe, wherein the periphery region is of a generally rectangular shape having: - a first flank side and an opposite second flank side parallel with the first flank side, the flank sides (2, 3) running along a longitudinal direction of the subframe, and - a first end side and an opposite second end side parallel with the first end side, the end sides (4, 5) being transverse to the flank sides (2, 3), wherein the flank sides (2, 3) have a linear density lower than that of the end sides (4, 5), and the end sides (4, 5) have a bending stiffness higher than that of the flank sides (2, 3), wherein either or both of the first end side and the second end side are provided with a reinforcement bar (4b, 5b) for increasing the bending stiffness said end sides (4, 5), wherein the subframe is configured to be slidably receivable within a filter plate frame along the longitudinal direction of the subframe, and wherein a supporting surface is provided on a first planar side of periphery segments forming the flank sides (2, 3) the supporting surface being configured to support the filter plate subframe on a corresponding receiving surface of an associated filter plate frame. characterized in that the subframe comprises separate periphery segments (2a, 3a, 4a, 5a, 6a) attached to each other so as to form a continuous periphery region of the subframe, such that the periphery region surrounds and delimits an open region of the subframe, wherein the periphery region is of a generally rectangular shape having: - a first flank side and an opposite second flank side parallel with the first flank side, the flank sides (2, 3) running along a longitudinal direction of the subframe, and - a first end side and an opposite second end side parallel with the first end side, the end sides (4, 5) being transverse to the flank sides (2, 3), - a first flank side and an opposite second flank side parallel with the first flank side, the flank sides (2, 3) running along a longitudinal direction of the subframe, and - a first end side and an opposite second end side parallel with the first end side, the end sides (4, 5) being transverse to the flank sides (2, 3), wherein the flank sides (2, 3) have a linear density lower than that of the end sides (4, 5), and the end sides (4, 5) have a bending stiffness higher than that of the flank sides (2, 3), wherein either or both of the first end side and the second end side are provided with a reinforcement bar (4b, 5b) for increasing the bending stiffness said end sides (4, 5), wherein the subframe is configured to be slidably receivable within a filter plate frame along the longitudinal direction of the subframe, and wherein a supporting surface is provided on a first planar side of periphery segments forming the flank sides (2, 3) the supporting surface being configured to support the filter plate subframe on a corresponding receiving surface of an associated filter plate frame.