Exported model (3ds, x) without some faces

I used simple plane with extrude option to made walls and hole for windows of my flat. When I was try to add UV texture in UV FACE SELECT mode some faces of extruded plane doesn’t represents. I set Twoside button on Texture face to show faces. Then I exported model in .x, .3ds files but same faces dissapear and model seems hollow (like in attach file).
All suggestion are welcome.
Thanks in advance.