…how do they work?
The liners are installed from the top of the stack once the chimney pot has been removed. Access to the stack must be safe and installing liners cannot be carried out of ladders and roof ladders so a scaffold is generally required. The liner is then pulled down the flue and terminated in the fireplace opening in one of two ways.
1. A plate is inserted through a hole made in the breast wall in the line of the flue and the liner is connected. The plate is then sealed and the hole is re-bricked ready for plastering.
2. A specially made gather is made to fit up inside the fireplace opening and the liner is connected to its spigot. The gather is then sealed to the chamber walls. This method can only be carried out if the aperture is larger than the diameter of liner used.
The second method is used when a liner installation is carried out in a decorated room.
Once the liners are down and sealed the flues can be back-filled using vermiculite insulation. The pots are then replaced and suitable terminals fitted.
After the installation is complete we would carry out a spillage test to ascertain the final working opening size of the fireplace chamber. By lining the chimney you are reducing the free area of the flue, which means the amount of gases that used to go up the flue, decreases. This has an effect on the opening size. The opening may have to be reduced using slips or by means of a glass header slip.
If you specify a larger opening size prior to installation then the use of a chimney fan would be advised. All flue work should be notified to local authorities as set out in Document J building regulations.