I bought an old three family a few months ago and it needs all new doors. It had old horse-hair plaster so I just covered it up with sheetrock. All of the door jambs are very different in width. The doors are also very different in size seeing that this was a very old house. I just stripped the doors out now its time to replace. I know home depot only carries the 4.5 width door jambs in the store. I really do not know much about how to measure the jambs to know which ones to get. Most of the jambs measure around 5 inches but there is now sheetrock over the jamb. So do I measure the sheetrock as well for the jamb width? Or is there a way I can buy the standard 4.5 jambs with and adjust the door somehow to fit the width that I have now? I guess what I am trying to ask is- when measuring the jambs, do I measure just the wood in the jamb or do I have to measure the sheetrock along with that? any help would be greatly appreciated seeing doors are very greek to me! thanks!