I've been searching around and I can't find the answer, so its time to ask: What clearances to combustables is required for a masonry chimney lined with clay flue tile? My chimney is lined with flue tile and I think it is constructed of masonry blocks (although most of what is visable is surrounded by bricks for asthetics). It looks like I probably have a 1" air gap between the blocks and the flue tile (not sure on that). Is the measurement taken from the flue tile or the masonry blocks? What about if a layer of bricks is also surrounding the masonry blocks (with or without an air gap)? Is the clearance the same if a flexible stainless steel liner is put into the masonry liner? Thanks in advance!