As a HETAS Registered Installer, one of our key proficiencies is the installation of flexible flue liners to reline existing chimneys.
In order to have a solid fuel fire or stove fitted to meet current building regulations, it is vital that the appliance is connected to a correctly sized and sound flue.
Most properties constructed prior to 1965 will have a square chimney stack, often measuring 9" x 9", or even larger for pre-Victorian homes. These chimneys were built for open fires, and a single stack often served multiple fireplaces in the home.
There are a number of reasons why you can't connect a wood burning or multi-fuel stove up to an old square brick chimney stack:
- A brick chimney is too large for stoves, which usually have just a 5" or 6" diameter circular outlet.
- A correctly sized and insulated flue is needed to draw the cooler gases produced by a stove.
- The lime mortar inside the chimney stack will have deteriorated, allowing fumes to leak into rooms.
- A mixture of tar and condensation can seep into the unprotected walls of the stack, causing staining.
- The rough, deteriorated surface of the chimney causes resistance to the flow of gases up the flue.
For the above reasons, and to meet current Building Regulations, we always reline square brick chimney stacks as part of a solid fuel stove or open fire installation.
Our recommended method of relining is using twin wall flexible stainless steel flue liner, which is then backfilled with vermiculite for insulation. The relined chimney is sealed at the bottom and top with steel plates, and we usually recommend having a multi-fuel terminal fitted on the chimney pot which incorporates a rain cap and bird guard.
We always specify the better 904 grade of flexible liner, which comes with a 25 year conditional guarantee. A slightly cheaper 316 grade liner is also available, which carries a 10 year guarantee, but our advice is that for the small saving made across the installation as a whole, it is not worth downgrading the quality of the liner used.
It is also worth noting that there are a number of manufacturers of flexible flue liner on the market, and a liner marked as 904 grade refers only to the raw material used to make the product, not the quality of its construction.
To ensure the safety of our staff we always work either from scaffolding or, if there is room for it on your property's drive, using our cherry picker to access the chimney stack.