chimney staining on outside?

[vipertec]

My chimney on the outside has wet staining/black creosote spots in many locations.It is a 8 inch masonry with square flu sections.The chimney was replaced about 5 years ago and the mason told me that the flu blocks do not seal between each other so this is possible with an indoor boiler that does get choked down.Is this normal or something I should be concerned about?

 

[sauer]

pics?
My old smoke dragon furnace did somewhat what you describe, basically stained the chimney crown somewhat. untill I put a epa hearthsone stove downstairs where the furnace sat.