A space efficient lavatory module for commercial aircraft includes an aft facing concave wall recess that provides a greater distance from an upper, forward facing portion of a cabin structure, such as an aircraft passenger seat to avoid having a passenger's head impact the aft facing lavatory or enclosure wall in a sudden aircraft deceleration. The aft facing concave wall recess also provides space for mounting of a protective cushion, in order to reduce a passenger's risk of head trauma in a sudden deceleration, as well as other items, such as a video monitor, a bassinet or infant bed, without inhibiting passenger movement.