An interlocking beam assembly for a frame assembly of a vehicle that includes an upper beam and a lower beam. The upper beam includes an upper hollow section integrally formed with a lower hollow section and a common wall shared by the upper and lower hollow sections. A notch is disposed in the lower hollow section of the upper beam at a select portion along a length of the upper beam. The notch is defined at cut edges along a bottom wall and side walls of the lower hollow section. A lower beam is configured to extend substantially perpendicular to the upper beam and attach in the notch in the upper beam between the cut edges of the side walls in a manner that bridges load paths across the notch in the upper beam.