If I were doing it...I would make the door first...then duplicate 3 faces on the sides and top of the door...then you can extrude them out to the required width. Does this make sense mate?? If not I will post a pic or 3 or a video for you.
cheers bullet
bullet1968
"A Darkness at Sethanon", a book I aspire to model some of the charcters and scenes