Questionable definition of indoors.

[Mas Tnega]

As long as you remove no more than the outer walls of a building, you can place an indoors only room (such as a cell or execution chamber) in that location.

[Stardog]

And is there a difference between the "Foundations > Building" and the "Materials > BrickWall"

I'm having tons of problems with these. Why can't we just use BrickWalls to build interiors?