Adding to what Ricewagon said in response to the UV mapping,
I agree that the walls are best extended past the UV space to occupy the amount of space it takes up in world space. For instance, if I have a wall that is 300cm in height, and 600 in width, then I’ll change the UV Grid in the UV Editor to match the settings. In Maya, you could change the “Length and width unit” amount to be “6.” One unit would equate to 100cm, so change the Unit amount to match the longest or tallest part of you wall. Once it’s at 6 units (your “grid lines every ___ units” should still be at .1), and making sure that the “Grid Numbers” are checked to “On axes,” simply scale your Wall UVs to match its size in real world.
Firstly, you’d take the UV shell of your wall and change the pivot of it to be the bottom left corner of the shell, and then snap the whole shell into the corner at 0,0. Then simply snap the top edge of the wall shell to “3” on the number grid, and snap the width (right edge) of the wall down to “6.” This will mean that your wall’s UVs now take up real time space, and the material you apply to it and display as it was most likely intended.