When installing a full mantel surround, it is critical to remember what the mantel
is doing for your fireplace.  It is a transitional piece to bridge the wall to the material
around the fireplace opening.  Think of it like a picture frame for your fireplace opening. 
       When you have a situation like the one illustrated below, a full surround doesn't work, because the material around the opening is the same as what's on the wall.  It's kind of like having a picture frame mounted on the wall, but the wall itself is the artwork! 
       What probably should have been done here was the installation of a mantel shelf instead.
 

What NOT to do:

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