How to Build a Fine-Grained City: Party Walls, Point Access, and Granular Blocks

Two independent walls face to face is a much simpler solution because it allows both structures to be structurally independent.

It is also safer because stupidity or neglect in one structure does not always impact the adjacent structure...though of course it can.

[edit: this is my favorite wall assembly for light construction https://www.usg.com/content/dam/USG_Marketing_Communications...]