hello!
ive managed to apply one boolean correctly to my model. there is a T shaped hole where the building will fit after CNC but the rest of the buildings just wont boolean properly!
can you really only boolean one time per object?!?
Boolean often leaves extra points and vertexes when working on complex shapes. You might want to examine your shape in wireframe mode and look for vertexes where you don’t intend them to be.
http://www.pasteall.org/blend/19364
well heres the blend file. i cant find anything wrong with the ‘terrain’ that i want to cut the cube shapes out of. (buildings 1 - 19 are supposed to cut their shape out the landscape for CNC cutting the landscape) eugh! this is a nightmare 
ok. after looking at previous models ive looked at thebuilding that did work. it looks like i made that building the wrong way (i just drew vertices around it and extruded it without making the faces quads or triangles) so im going to try that on another building and see how it goes!. ill get back when im done.
ok. what seems to be the problem is all the buildings ive made are crazy with doubles or something. so for simplicities sake what im doing is deleting all but the plan frame of the building and then applying the boolean ‘difference’ it with the landscape.
Can you just duplicate parts of the mesh of the “crazy” building to use that as a separate object for boolean?
well what ive done is just re-create the buildings and then boolean them. unfortunately im going to have to try something else because to get the model CNC’d it would cost me 700 pounds. which is too much. so im looking at other ways to do this.