Booleans

I've done a lot of rendering and model building, specifically homes and kitchens with Blender. I am trying to import a .fbx file.  I started with a complete foundation  that included booleans to the walls.  While in Blender I applied the boolean and exported only the selected foundation. I imported really funky.  So, I decided to simplify and import a single wall with an applied boolean for a window.  It imported in with planes on the front and back of the boolean location.  The boolean cube extended past both sides and top of the wall in Blender. And, the Normals were good.  What am I missing?