Chimney Liners
The flue is a duct for smoke and waste gases produced by a fire, a gas water heater, gas or oil furnace or other fuel-burning installation to be transitioned through the chimney. It is imperative the material that makes this duct or flue be made of proper materials and in good condition. The chimney flue can be made of a variety of materials. The most common is clay or Terra cotta flue tile. All the joints in this system are to be sealed and smooth and the tiles must not have any cracks, gaps, or holes. Damage or imperfections in the flue material could allow the byproducts of combustion to enter the home or other parts of the chimney. If creosote gets through any imperfections in the flue it will build up in places that cannot be seen or swept out. In the event of a chimney fire these unseen deposits become an additional source of fuel for the fire. The flue lining material is the first line of defense to protect your chimney and home from damage during a chimney fire. The importance of the integrity of the flue lining material cannot be overstressed.
Flue tiles are to extend the entire height of the chimney and extend not less than 2 inches above the crown or splay or wash of the chimney. When a flue tile is heated in normal use of a fireplace or appliance the heat will cause the flue tile to expand in length. When the tile cools it will shrink in length. If the tile is less than 2 inches out of the crown the concern is the tile could slip below the crown surface. (2019 NFPA 211 7.2.13.3) Then when the flue is reheated it will expand and may collide with the crown causing damage to either the flue or the crown or both.
