A structure having an area separation wall including: a first building unit; a second building unit; and an area separation wall having only outer membranes. Preferably, the area separation wall is fire resistance rated. The outer membranes provide acoustic attenuation without adversely affecting the fire resistance of the area separation wall. The area separation wall provides improved thermal resistance. In one embodiment, the area separation wall includes: an interior support structure and at least one outer membrane on each side of the interior support structure. The outer membranes provide acoustic attenuation. Between the outer membranes is a substantially organic material barrier. The structure may also include a tying structure connecting the area separation wall to the first unit and the second unit.