Improved exact approaches for row layout problems with departments of equal length.

•We study multi-row facility layout problems with departments of equal size.•We prove that spaces of unit length suffice to obtain a global optimal solution.•We propose new integer linear and semidefinite optimization models.•We increase the largest instances solved to optimality from 16 to 25 departments.•Using a bundle method allows us to determine To paper: high-quality solutions for large instances.