brick above lower wall

[MPDesign]

alyxduncan,

Try a molding ployline around the exterior, set your size, height and required profile.
If you left click near the exterior side of one of the exterior walls it highlights the area immediately around the building. Then in the subset of tools that show up at the bottom or right side of your screen is where you can find the command. or main menu Build, Trim, Molding Poly Line.