Hi everyone,
I have an older house and want to install a standard size metal exterior door in the back. Currently, there is a wooden door that has been cut to size. I took down the molding around the door and found that the door has been attached to 2X4's, which is flush to old plaster. There is no oversize roughed in frame for me to install a standard size pre-hung door. I was thinking I would have to rip out the plaster around the door, rip out the frame that is there, install a new door frame to fit a standard door, cut around the siding outside to accommodate the new door size, install the new door, plaster / drywall around it, and finish with molding and paint.
Does this sound right or am I over my head in all of this. I am pretty new, so I am not too sure if this is something I could handle?

 

Sounds about right. You'll need a rough opening 38 1/4" X 82 1/2" (measuring up from the finished floor level) to install a standard 36" prehung exterior door. If the wall is load bearing, it would probably be wise to install a header over the opening as well.

Often you can leave one stud existing on one side (usually the side with the electrical switches) and just tear open the wall back to the next stud on one side only. Then when you put the header in, you can fit it between existing studs and when you put the trimmers underneath it, that will create the R.O. for your door. Leaving as much plaster as possible makes patching in a lot easier.

You may also find that once you remove your old door, you may need to fill in the bottom of the opening with some 2x6's or something to build the door sill up to your finished floor height. Often, old door sills were just set on the floor joists, and when you remove the old door... surprise! You can see right into the crawlspace! But that's a good time to pack a bunch of fiberglass under there.