I need to have the crown repaired on what I think is called a exterior flue enclosure for a wood fireplace. I believe the construction was wood frame with cement board and brick face. I am sure brick face was used. The problem is the crown is asphalt shingle which is worn at the corners that overhand each vertical wall overhang of the enclosure. One possible problem I see on the original installation is this asphalt shingle crown was not pitched from the flue to the outside. How should the repair be done on the crown? Should it be pitched?