Do I need my chimney lined

Do I need my chimney lined?

Liner v’s no liner

One of the most common questions asked on the HETAS Consumer Helpline is Do I need my chimney lined?

There is a regulation that says your installer must satisfy themselves that the chimney is free from defects and suitable for its intended use. When he or she checks your chimney they may find that the only way to provide you with a compliant and safe installation is to line the chimney. If there is any risk that the chimney could leak fumes in to the house they must line it with a suitable re-lining material. There are quite a few choices of system and the most popular is the flexible stainless steel type. It may be an essential part of your installation.

If any work undertaken on the chimney, including installation of a new liner, is done in conjunction with the installation of a heating appliance, then that work is a controlled service and must be undertaken by a competent person, such as a HETAS Registered Installer or approved by your Local Authority Building Control department.

Why line a chimney?

Chimneys are lined for a number of safety reasons. New chimneys may require relining to suit the fuel type being used (a gas flue liner may not be suitable for other fuels). Chimney systems that predate 1965 will often require a modern lining solution for the following reasons:

  • The flue may have lost integrity and can leak smoke into rooms or other part of the building
  • Condensates or tar can seep through chimney walls causing staining, inside or outside of the building
  • Lining with insulation included can improve the operation of the appliance and flue – particularity important when the chimney is situated on an external wall
  • Defective flue systems may be eroded and rough. Thus will cause frictional resistance to the flow of the gases resulting in poor up-draught
  • Large flues over 200mm, particularly ones containing voids, may affect appliance performance. Some appliance manufacturers specify smaller flues for efficient operation

The BFCMA has produced general guidance on the selection and installation of flues and chimneys for wood burning and multi fuel appliances in residential properties. Click here to view the guidance document. Always consult a HETAS Registered Installer prior to undertaking any solid fuel installation work.

The British Flue & Chimney Manufacturers’ Association is Britain’s only Trade Association for factory-made chimney products and works closely with Government, public bodies and other organisations to further the interest of the chimney & flue industry. Click here to find out more about the BFCMA.



Flue size update

doc_jIn October 2010 our Technical and Training Manager Andy Mathews issued an update on flue sizes, the issues highlighted by Andy remain prominent and can be read below. Andy writes: Through the ongoing HETAS inspections process we are realising that there are a number of installations that are failing in respect of the flue installation. One of the more common areas of non compliance has been recognised by our inspectors and these concern flue sizes and those associated flue connection arrangements. It has been observed that 125mm flues have been fitted instead of the required 150 mm flues. There is clear evidence in failure to observe the appropriate Building Regulations in force controlling the installation of flue liners.

All appliances up to 30kW

The Building Regulations 2010 state that appliances burning any fuel and rated up to 30kw would require a minimum 150mm diameter flue liner. The Building Regulations are more stringent than manufacturers’ instructions; therefore, the Building Regulations must be abided by unless the manufacturers’ installation instructions state a larger diameter. The quoted flue liner size should be as per manufacturer’s instructions but in all cases should be at least 150 mm diameter or larger where appropriate. The following extract confirms this: The Building Regulations (2010) Approved Document J: page 30, 2.6, that “For multi-fuelled appliances, the flue should be sized to accommodate burning the fuel that requires the largest flue.”

Smokeless Fuelled Appliances: and Defra exempted Appliances up to 20kW rated output

A DEFRA exempted appliance is one that meets the standard for burning non-authorised fuels in accordance to the Clean Air Act. The Building Regulations, Approved Document J, Table 2, suggest you may line the chimney with a 125 mm diameter liner for burning only authorised smokeless fuels or the fitting of an exempted appliance burning one of the fuels listed in the exemption record for that appliance. This assumes that the appliance manufacturer does not specify a
larger diameter flue is required.

Note: This is not to be confused with connecting flue pipes, where the connecting flue pipe should have the same cross sectional area as that of the appliance flue outlet, and should not be smaller than the size recommended by the appliance manufacturer. Where possible the Connecting flue pipe should be kept to the shortest practical length.

Registered installers should also refer to Chapter 11 of the HETAS Technical Handbook.

Andy Mathews
Technical and Training Manager