Spawning seems to differ depending on where the spawn point is

Unity 4.6. I have an object (a house) that is in the world. I have other objects (furniture) that spawns in via script. So to spawn the furniture in the correct location (there are lots of houses) I store the difference between 0,0,0 and the furniture position. Then the algorithm take the transform position of the house in which the furniture will spawn, and adds the stored value to the parent transform position.

For 2/3 of the houses in my world this works great. But oddly, the very same algorithm with the math 100% correct, spawns things outside the house instead of inside. The only theory I can come up with is based on the location of the GUI (000) the houses where it is broken seem to be on the other side of that axis. (mostly x/z position).

What would cause this? And how can I fix it? I really find it highly inconvenient to not have the same algorithm work the same way throughout my world. Why would it work differently based on where the houses are located?

I got it working. Someone explained that in run time all transforms are global and only in the editor can you do local. So the issue was I needed to parent the furniture to the house and then use the local position and it all started working correctly.