My fabric is stored up stairs in the guest room closet - so when I'm going to go through my stash I just say "I'm going upstairs!" Then my hubby knows not to bother me and to answer the phone!
My sewing stuff is all downstairs in the lower level (ok, the basement), so I just say "Going downstairs!" and hubby knows to follow the same rules!
So, I guess I call my sewing room studio "Upstairs" or "Downstairs"!