DO I HAVE TO FIT A CHIMNEY LINER?

DO I HAVE TO FIT A CHIMNEY LINER?

Regulations state that before an installer proceeds with any work they must first check that the proposed chimney is free from defects and is suitable for use with a stove. For most installations, especially in older houses and those that predate 1965, the only sure way to deliver a safe and building regulations compliant chimney for use with the stove and prevent smoke and fume leaks is to line it with the appropriate liner. Flexible stainless steel liner is the most common and cost effective method currently being available.

You may hear a homeowner state that their chimney was already lined when they originally had their gas fire fitted so why does it need a new liner? Chimney liner for stoves and gas fires are constructed differently with different safe operating temperatures and are therefore only suitable for use with that particular fuel.

It's worth noting here that any work undertaken on a chimney, for example opening up the fireplace or installing a stove and liner, is regarded in regulations as a 'controlled service' and must be approved by the local authority Building Control department. Alternatively, in England and Wales such work can be carried out by an installer who currently registered with a government Competent Persons Scheme such as Hetas or OFTEC who can self-certify that their work will comply with building regulations without the need to refer it to building control prior to starting.

There are a number of excellent reasons for installing a flexible liner...

• Older chimneys, especially those used with an open coal fire for many years, will probably have developed failing mortar joints because of poor combustion and its resultant acidic condensates eating away at them. This could potentially cause the chimney to leak when these joints come into contact with the high temperature flue gases that a stove can create. A one-piece flue liner correctly installed will prevent potential leaks.
• Some older chimneys contain large voids and bends which will affect the performance of the stove by slowing and cooling the flue gases as they exit the terminal making the stove harder to light among other things. On some larger Victorian houses two flues often share the same stack with only a single course of poorly laid bricks between them and which, over time, often fails because of very loose or sometimes even missing mortar and bricks. Poor sweeping practices in the past won't have helped either. A one-piece liner provides a continuously smooth and consistent diameter flue with a direct relationship to the diameter of the flue outlet on the stove to deliver improved and dependable operation.
• Condensates or creosote tar can can seep through chimney walls causing staining, inside or outside of the building – admittedly this is mostly due to the poor combustion of wet wood but could also be due to a chimney on an outside wall that is subject to cold prevailing winds that severely cool the flue gases in the chimney to create ideal conditions for condensation. A flue liner will partially insulate the flue gases to keep them hot and also help eliminate potential condensation and subsequent leakage. Insulating the flue liner as well would also have some advantages.
• Many chimneys have inconsistent, rough and poorly applied interior mortar joints on the basis that no-one is ever going to see them. In addition some concrete or clay liners in post-65 homes can often have the liners positioned the wrong way up with incomplete mortar joints again, because no-one will see them. Both of these scenarios will cause frictional resistance and cool the combustion gases to adversely affect the flue draught and in turn the stove's operation. Clay and concrete liners pointing the wrong way can also cause condensation leakage. A flexible flue liner will create a smooth and speedy flow of combustion gases which won't have time to cool when the stove is operated correctly.