The installation of this back door is part of a much larger project involving pretty much the whole house (more post on the other work will be posted soon). Originally, there was a sliding glass door in this spot. Unfortunately, the door was poor quality and not installed correctly.
Framing in the new door required adding a proper sill that was missing from the old door. That required cutting the opening higher so the door would fit properly. After that the real work began, the outside of the had three layer of siding making for and extremely thick wall. So a lot of custom cutting and fitting had to be done in order to make the door look like it belonged there. That and some extra trim work to cover old joints and cuts. In the end a perfect fit. I'm very happy with the out come of this installation.