While the requirement for installing a mantel shelf above a masonry fireplace opening without a wood insert installed is normally 12" measured from the base of the mantel to the top of the fireplace opening, the installation instructions for the manufactured wood insert should be referred to for any additional clearance requirements. To answer your question, there is no nationally-accepted code requirement for installing a mantel above a wood insert.
Submitted by:
Will M.
on July 5, 2019
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