A flue is the vertical passage inside a chimney that carries smoke, gases, and heat from the firebox or a heating appliance up and out above the roofline.
Every working fireplace, wood stove, or furnace that vents through a masonry chimney needs its own flue sized to that appliance, since a flue that's too big or too small hurts draft and can let smoke back up into the room. Most masonry chimneys have a lined flue, either clay tile sections stacked one on top of the next or a metal liner, rather than smoke traveling directly against bare brick and mortar.
The flue is the part of a chimney you can't see, so problems inside it often show up as symptoms elsewhere first, like soot streaking on the outside brick or a smoky smell in the room when a fire's going. Draft depends partly on the flue's height and cross-section relative to the appliance it serves, which is why a homeowner shouldn't just swap in a bigger stove without checking whether the existing flue can handle it. On an older chimney with a deteriorated liner or none at all, we generally recommend relining before the fireplace goes back into regular use.
More masonry vocabulary from the glossary.
The services where this term comes up.
Chelo's Brick & Stone serves Hillsville, Galax, Wytheville, Fancy Gap, and Independence, VA. Call for a straight answer and a free on-site estimate.
