Boolean operation being done backwards

Support Modeling
1

Sort of.

I have this problem that when I’m trying to ‘punch a hole’ for a window in a structure, instead of a hole I end up with a protruding block.

Please see here:
http://www.diamantstudios.ca/Gemeines/Blender_Boolean_01.PNG http://www.diamantstudios.ca/Gemeines/Blender_Boolean_02.PNG

What gives?

TIA

2

Make sure all your face normals are pointing outwards by removing any doubles (W / remove doubles) and recalculate normals with Ctrl+N
Ensure you have set the correct boolean operation in the boolean modifier settings

3

I had the same problem when I extruded an object from top down and then attempted to use booleans. Extruding from the bottom up was the work around for me.

4

I did extrude from the bottom up, but thanks for the heads-up: I’ll try to make it a habit to continue extruding this way.

Thanks Richard, recalculating the normals did the trick.