top of page

Flexible chimney liner

Flexible chimney liner is recommended for many solid fuel installations, but what exactly does it do?

Solid fuel flexible chimney liner is made in two different grades, a 316 grade steel and a stronger 904 grade steel. Most 316 grade flexible chimney liners are suitable for wood burning installations and occasional smokeless fuel burning but a 904 grade is recommended for very heavy usage or when burning mostly smokeless fuels as these fuels produce hotter gases.

Solid fuel flexible chimney liner should not be confused with a gas liner which looks similar but is produced using aluminium. Gas liner cannot tolerate the temperatures created by the flue gasses produced in solid fuel combustion.

Solid fuel flexible chimney liner is made with two layers of steel which are crimped tightly together and is often referred to as twin wall for this reason, the tough outer wall protects the liner against rough edges and the smooth inner layer ensures a safe passage for escaping flue gasses without causing friction.

A flexible chimney liner creates a chimney within your chimney, this stops smoke escaping from any vulnerable spots in your chimney and also decreases the internal diameter which in turn allows the flue gasses escape faster and stay warm for longer.

As solid fuel flexible chimney liner contains no insulation between its two layers, most flexible chimney liner manufacturers recommend that you insulate around the liner and many increase their warranty if you do so.

Insulating your chimney will help to reduce condensation build up which can corrode your liner and insulating also helps to increase draw by helping flue gasses stay warm and rise.

Insulating around a solid fuel flexible liner can be achieved in two ways. Firstly by wrapping the liner in rock wool or an insulating sleeve or secondly by pouring a loose fill insulation around the liner such as vermiculite, which can be mixed with concrete if required producing a semi set material.

When installing a solid fuel appliance, a flue pipe is taken from the stove which connects to the flexible liner inside the chimney above the register plate or closure plate using an MA (main appliance) adapter. The flexible liner should be in one continuous length with no joins and terminates at the top of the stack.

Flexible chimney liner is available in various diameters such as 5” (125mm) and 6” (150mm) to match the appliance outlet. It is possible to use a solid fuel liner with a diameter larger than your appliance outlet by using an increasing MA adapter eg a 5”-6” increasing MA adapter; but it is not recommended to use a liner that is smaller than the diameter of the appliances flue outlet as this restricts dangerous flue gasses from leaving the appliance quickly and safely.

North Wales Stoves ltd stocks only high quality flexible chimney liner which is available to buy from our HETAS registered showroom in Betws Yn Rhos, Abergele, Conwy. We are also registered under HETAS to install and certify solid fuel installations using a flexible chimney lining system. For more information, or to book a free estimate in the North Wales, Cheshire or Wirral area contact 01745 822344 or email

Featured Posts
Recent Posts