Chimneys and Flue Types

The Flue information provided within this section should be used as a guide only. A professional fireplace survey is recommended prior to purchase/installation of any stove or Fireplace.

Once you know what chimney type you have you will need to check the integrity of the chimney stack and may need liner, read our Twin Wall section to find out what this is and what you may need.

The conventional brick chimney - clearly defined by a chimney stack and pot on the roof. Usually found in older houses that were constructed earlier than 1960. The Class 1 chimney is identifiable by 7" (177mm) or greater diameter flue. The existing chimney must be structurally sound, please have your chimney checked by a professional before the installation of a new fireplace, wood burning stove or multi fuel stove.

Hollow concrete flue blocks create a flue up through the property usually ending with a ridge vent on the roof. Modern houses generally later than 1960 often have a pre-cast concrete chimney system, identifiable by a rectangular box section flue and a terminal, as illustrated in the picture.

A metal flue box situated behind the fire connects to a series of metal flue pipes run up through the house terminating with a pipe and terminal through the roof. Either an older house where the existing chimney has been lined by a proprietary steel flue or a newer house with a steel flue built in. This chimney type is identifiable by a 5" (130mm) diameter flue and a steel flue terminal.

Where no chimney or flue is available. A quiet but powerful fan situated on an outside wall expels the flue gases from the fire. Mains electricity required.

Where no chimney or flue is available. The fire vents directly outside through a horizontal twin wall pipe. These fires are glass fronted. No mains electricity is required.

Flue Safety

It is extremely important that the right type of flue is used for the fire or stove that you plan to have installed within your home.

A wood burning stove should not be connected to a flue pipe that is used to service a gas appliance. This type of flue will have an aluminium lining and will be rather thin, when connected up to a wood stove it will soon corrode or burn out, which could be potentially very dangerous and could cause a fire.

If you have a wood burning fire or stove, remember that it is a prudent to get the chimney swept on a regular basis. Doing this will prevent the build up of creosote in the lining. A cool chimney, which is usually the case in the Uk could allow third degree creosote (sometimes called glaze creosote) to form on the in. This is much denser and more difficult to remove than regular creosote. Creosote is a flammable by-product of burning wood.
If the creosote is allowed to build up, and the chimney gets hot, it can catch alight and get out of control this is known as a chimney fire and should not be encouraged under any circumstances. Having your chimney swept on a regular basis will help prevent this. An alternative to sweeping is to have the chimney lined. These days, flue linings made from steel have been developed for use with different fuel type fires. There are also options for Twin wall linings, more information can be found in our Twin wall section.

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