Flue Pipes For Stoves - How To Identify Your Flue
With the amount of confusion I hear from customers on flues I've put together a simple identifier, so
that you make correct and informed decisions.
Firstly Class 1:
Now, this is for a fire using as its fuel either solid fuel, such as coal, wood or any renewable such as
peat, as well as gas or oil. We see Class 1 flues all the time. You see a chimney is a Class 1 flue, but,
that doesn't mean it has to be made from brick. Today a flue can be made from vitreous enamel,
steel, volcanic pumice and come in a variety of colours as well as gloss or matt finish. The diameter is
usually at least 7 inches (18cm).Class 1 is ideal for the larger fire as more air (smoke) will be
transported up the flue.
A less robust type of flue than the Class 1, generally used for gas fires. It can also be built from a
variety of materials, but mostly is constructed from aluminium. You can turn a Class 1 into a class 2
by adding a liner. The smaller diameter and construction materials are used for the smaller "reduced
draught" gas fires, certain gas stoves and glass fronted gas fires.
Class 2 (Precast):
This is usually seen on newer properties. Basically its a block system that is incorporated within a
new builds wall. If you look at the roof you'll notice a raised edge ridge tile, this is the termination point
for this type of flue. As the Class 2, its fairly limited in its fume transportation. So there is a reduced
range of stoves and fires that its compatible with.
A recent entrant on the flue market. They are based around catalytic converter technology. All of the
properties released from the burning gas come in to the room. Please note this is not all heat. For this
reason there are restrictions on the appliances uses. Described as 100% efficient, the output of the
appliance must be related to room size. This generally is with in the range of 30-40 cubic meters. Its
very important that the room is ventilated, the vent size is dictated by both the manufacturer and
A very unique flue, the only one that DOESN'T make use of air in the room to feed the fire.They are
double skinned with the exhaust fin traveling through the core with fresh air drawn from outside the
building via the outer wall of the flue.Because of this there is no need for room ventilation. Often
described as "room sealed.Due to their flue construction, all fires that use this system are glass
If you have a large gas fire and the Class 1 option isn't available, this type of flue is a good fall back.
The fumes are passed via a pipe, outside and are helped on their way by an external fan. Whilst they
may solve your construction problems, they will be dependent on electricity, so if your power is cut
your gas is automatically shut off. Great, sitting cold in the dark! There is also some times a slight
problem with the level of noise from the fan unit itself. This will depend on how close the fan is to the
fire, the fire type and flue pipe material.
This is meant as a guide to identify your flue type. Other things to bare in mind is the height of your
flue when it terminates outside your home, its actual external appearance. As stated above consult
with either a CORGI or HETAS fitter. Or if you are attempting this yourself your local planning officer
or current building regulations.
I hope this has been of some help & remember to keep the home fires burning!
Chimney Repairs Suffolk County