Success! Thanks again

Kriscidious's tutorials are good; and ultimately you will need some very good model organization: Make your floor plan a component. What you include in that component depends on the flexibility you want/need. You can Copy that floor plan component off to the side and edit it, after your edits are finished, erase it, your plan in the house will be changed as long as you didn't select "make unique". there are other ways too but this technique is consistent for me.

If you are drawing with profiles turned on, a thicker line usually indicates that it has not been successful in sub-dividing the surface...and is still therefore regarded as a profile. Maybe it didn't quite make it to an edge or is in some way still separate from the surface. Check that when you select the surface on one side of the line, that the selection doesn't simply ignore that line and extend beyond it.