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Chimneys and Lining

What is Chimney Lining?
The function of a chimney is to safely remove the products of combustion from a fireplace or appliance to outside of the building, without causing any danger to the occupants of the house. A chimney works because hat air rises and moves from high to low pressure. Factors such as running the appliance at a very slow rate or cold air leaking into the flue will cool the gases and affect the performance of the chimney. Lining systems are designed to replace the flue in an existing chimney, with dimensions appropriate to the appliance. Insulation may be added or integrated into the new flue systems to improve the efficiency of the draught. This is a particular requirement for external situations. The Lining method of a chimney and materials vary.

Why Line Chimneys?
Chimneys are lined for a number of safety related reasons. The illustration shows two types of chimney systems that pre date 1965 will often require a modern lining solution for the following reasons:
1. The flue may have lost integrity and can leak smoke into rooms or other       parts of the building.
2. Condensates or tar can seep through chimney walls causing staining,            inside or outside of the building.
3. Lining with insulation included improves the operation of appliance and     flue (particularity important when the chimney is on an external wall).
4. Defective flue systems may be eroded and rough. This will cause                     frictional resistance to the flow of the gases resulting in poor updraught
large flues (over 200 mm) particularly ones containing voids may affect       appliance performance. Some appliance manufacturers specify smaller         flues for efficient operation.

Chimney faults
Before having a liner installed in your chimney, you should have it swept to remove soot and tar deposits by a professional chimney sweep. For those that already have a chimney lining, a competent sweep will be able to inspect for the following faults:
1. Liners fitted upside down
2. Out of line or overlapping liner
3. Obstructive ledges hindering updraught
4. Protruding cement joints
5. Liner removed during previous service work or installation
6. Damage through incorrect sweeping
7. Masonry damaging the liner
8. Blocked terminal (cowl or rain cap)
These faults can lead to a number of problems with the operation of a solid fuel appliance. More importantly, faults with chimney lining can pose a risk to the safety of household occupants and should be rectified immediately.