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What is a Flue Extension?

Lori Kilchermann
Lori Kilchermann

A flue extension is an additional length of flue pipe added to a chimney. The flue is a pipe which leads from a furnace or stove to the outside of the building. Smoke, soot and dangerous gasses flow away from a fire and through the flue. The flue extension often is used to improve the draft of an existing flue pipe and can be constructed of clay tile, galvanized metal or tin.

Many times a building is constructed as a lone structure on a piece of property. At the time of construction, the chimney may have had adequate flow and been sufficient for the job. Over time, other buildings may have been constructed, or perhaps trees planted had grown and matured. This disruption in the way the air currents flow around the building may impact the drafting characteristics of the existing chimney system. A flue extension may be required to elevate the top of the flue into a different air pattern and restore the correct draft to the chimney.


Whether conforming with changing building codes, working around additions near a structure which changed the draft to a chimney or building for aesthetic reasons, a flue extension is a relatively easy upgrade to an existing chimney. There are many companies producing flue extension kits that the average homeowner can complete in a weekend using minimal hand tools. The flue extension kits typically include not only a section of flue material, which can be purchased in a matching product to the existing flue, but also a reinforcing and stabilizing wire guy system and a flue cap.

It is often a wise idea for people to clean and service a chimney at the time of adding the flue extension. The opportunity to be on the roof of a structure does not present itself often, and full advantage of the situation should be taken when it does. Most flue extension kits are complete with easy-to-read and easy-to-follow instructions detailing the installation procedure. It is often wise for people to test-fit the entire system prior to permanently fastening any part.

When purchasing a flue kit, individuals should be sure to have the original flue material type and size as well as the needed length. It is also wise for people to inform the sales associate of the type of gasses that will be flowing through the extension—wood smoke is different than natural gas exhaust, for example. This type of attention to detail prior to purchasing can save money, time and frustration.

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