It seems likely that the northern wall of Room H14 was built in two phases: in the first phase, the space was only partially enclosed on the eastern side by opus reticulatum wall 7285, whose western limit aligns with walls 7079 and 7080 to the north. In the second phase, this wall (7284) was built to fully enclose the space on its northern side, covering and putting out of use an earlier tufo slab floor (7315).

Concrete wall with tufo, tiles and large basalt stones near eastern end of northern wall of Room 14. Different building technique from the eastern opus reticulatum part of northern wall of Room 14, extending from the tufo pillar SU 7283 to meet the opus reticulatum wall SU 7285 and together form a northern wall of Room 14. The large basalt stones might be taken from other place and reused to build to wall. There is a gap in the middle between this irregular wall and the opus reticulatum wall. The modern concrete conservation fill the gap, so it is hard to tell if the gap was intentional when the wall was built, but the relatively big tufo block at eastern bottom end of the wall might indicate that the gap was intentional and could be a doorway.