A flue is basically a chimney or pipe which will carry away smoke from a stove or boiler, or an open fire. If you have an open-fire then you will already have a chimney, and due to the amount of draught that an open fire needs the diameter of this may be quite large. Each stove will have an outlet at either the back or top of it for connecting to a flue or chimney. This will be a much smaller diameter than a chimney, and each stove depending on the fuel it burns and therefore the amount of draught it needs will be a particular size. So for example a multi-fuel stove may need a 5 inch or 6 inch flue, or a wood pellet stove may need an 80mm or 100mm flue.

A flue system then is all of the flue components such as lengths of pipe, any fittings to hold it in place, a connecting piece to the stove and a cowl or cap for the top of the flue. There are two basic types of flue systems. Rigid flues for when an existing chimney does not exist, and flexible flues where you may have a chimney but it’s diameter is much larger than the stove manufacturer recommends, in this case we would line your chimney with a flexible flue of the appropriate diameter.

We offer some of the following flue services:

tickChimney cleaning

tick Chimney lining

tickChimney camera service including report

tickTar removal

tickDown-draft problems solved

tickCarbon Monoxide assessment



Rigid flues are used for stoves where an existing chimney does not exist, for example if you locate a stove on an outside wall, you can use install a flue to go through the wall up to the height required by building regulations. They are typically 316 quality. Examples are shown below: (Click on picture to see larger image)


Through the wall installation


New twin wall flue -Wood burning and multifuel stoves


Internal installation with a building enclosure


Internal installation without a building enclosure


Single wall liner – existing chimney – wood burning and multi-fuel stoves





































Flues come in a variety of diameters for attaching to your stove or boiler. These are 80mm, 100mm, 125mm and 150mm, and 200mm. We stock a full range of standard flues. Any irregular sizes can be ordered. They come in a variety of lengths from 250mm to 1250mm, as well as adjustible lengths. Also there are some angled bends such as 45° and 90 °bends and tees, as well as connection pieces, adaptors, fire stops and cowls/rain caps. In most cases the connection is made by a twist-lock system with locking bands.


Flexible flues are used for stoves or boilers where an existing chimney does exist. The flue acts as a liner as the outlet on the appliance may be smaller than the diameter of the chimney. Again they come in a variety of diameters, and can be cut to suit the length required. A typical installation will look like the drawing below, but please note that Vermiculite is also added to insulate flexible flue liners and this has been accidentally omitted from the drawing below:


Twin wall flexible liner – wood burning and multi-fuel stoves

FLUE ACCESSORIES: Downdraft solutions

Sometimes you may experience downdraft or updraft in your chimney, due to the prevailing winds or the location of your house. Now this is often less noticeable when you have an open fire, having less affect on your fire. However if you have a stove then as the flue outlet opening on this would be much smaller in diameter than a chimney, an updraft or downdraft issue could have a greater effect on your fire. If you experience updraft, where air is sucked up your chimney,  then we can fit a draft stabiliser which will help to solve this problem for you. Alternatively, if you experience downdraft, where wind blows down your chimney, then we can fit a h-cowl or a rotating chimney cowl, depending on the severity of the problem. All of these solutions are to ensure the efficient working of your stove.


The Department of Environment have drafted Building Regulations J 2014 and as part of this there is a Technical Guidance Document J which outlines the standards for flues. You can download a copy of the full document if you wish to familiarise yourself with the regulations pdf-iconTechnical Guidance Doc J Building Regulations 2014.

Flues may be made of steel, stainless steel, cast iron.

The basic principles of the regulations are:

  • That there is an adequate supply of air.
  • That the products of combustion are safely discharged to the outside air.
  • That the building is protected from catching fire.
  • A notice with the details of the type of heat appliance must be placed in a suitable place
  • That a check list detailing the construction of the chimney should be completed.
  • That a notice plate detailing the correct application and use of the chimney should be attached within the building.

Regulations require that:

  • the materials meet a certain quality standard
  • Direction – Flues should be vertical unless a bend is necessary. Horizontal flue runs should be avoided except in the case of a back outlet appliance, when the length of the horizontal section should not exceed 150 mm.

Source: Technical Guidance Document J Building Regs. 2014.

Other brief details:

  • Stoves: Either twin wall rigid flue is used of 316 quality or flexible flue. Rigid flue must finish 1m above the guttering, and flexible flue must go 1m above the top of a masonry chimney.
  • Boilers: Typically rigid flue of 316 quality. For our Twin Heat appliances a minimum height of 5m is required. For gasification, a minimum of 12 – 15 feet is required. Diameter is decided by manufacturer of appliance.
  • A masonry chimney can be constructed also.
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