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Building Regulations for Chimney Installations

Any work that affects an existing chimney (including installation of a stove or flue liner) or creates a new chimney is considered building work and sofalls withing the remit of the building regulations department of the local authority.

The government issue an approved document, which contains practical guidance on ways of complying with the requirements of the building regulations, which deal with combustion appliances. In the UK, Document J of the building regulations applies to flues and chimneys. These must be adhered to for safety and legality.

Building regulations

Fitting a flue liner/chimney system yourself

You must notify building control before installing any chimney (unless you are approved to self-certify, as are HETAS engineers)

You do not have to use a professional installer. If installing the stove into an existing fireplace/chimney and not using a new chimney liner then the installation is very straightforward for a person with average DIY skills. Installing a flexible chimney liner or complete twinwall system is a larger job and may involve ladders or scaffolding if external access to your roof is needed, but is still technically straightforward, so no specialist knowledge or skills are required.

If you complete the work yourself then the local council building control should be informed and they can then inspect the work on completion to sign it off. Alternatively, if the work is done by an installer who is accredited by one of the relevant Competent Person Schemes such as HETAS then they can sign off their work and provide you with a certificate.

Planning permission

This is not normally required. Installation of a stove and/or new flue system would not usually have anything to do with the local planning authority. If your property is a listed building then permission may or may not be required. If you intend your new flue pipework to run up the outside of an external wall then depending on the position (e.g. side or front of house) you may need to check with the local authority planning department.

Do I need to line my existing chimney?

Most houses built after 1964 should have a concrete/clay inner liner in which case you probably don't need to reline unless there is a problem with your existing system.

Older houses will normally just be exposed brick inside - it is not a legal requirement to line these older chimneys unless they are leaking, but there are often advantages to lining such as increased draw, peace of mind of having a sealed system top to bottom, and reduced risk of a chimney fire or leakage etc.

The existing chimney/flue should be swept clean before any stove installation and checked for condition and correct operation. A smoke pellet should be burned at the bottom to check for any leaks or blockages. Your local chimney sweep should be able to advise on your chimney condition if you are not sure.

We always advise that chimneys in older properties should be lined.

You must notify building control before installing any chimney (unless you are approved to self-certify, such as HETAS engineers).

Chimney design rules

  • The minimum chimney height recommended for the minimum performance of wood-burning and multi-fuel appliances is 4.5m from the top of the appliance to the top of the chimney.
  • The distance between the cowl of the flue and the adjacent roof/wall/structure should be higher than 2.3 meters.
  • A maximum of four bends (up to 45º angle) is allowed. In the case of four bends; a sweeping door in between the two outer bends is required.
  • In case of an offset; a maximum of 20% of the flue length can be non vertical (best practice).

Flue sizes

Most solid fuel appliances in the UK have either a 5" (130mm) or 6" (150mm) flue outlet on the top or rear of the appliance. You will normally then use the corresponding sized vitreous enamel flue pipe for the first section of flue from the stove to take you into the chimney. From that point, you will then usually have to change to a minimum 6" (150mm) flexible chimney liner or rigid insulated flue system. If you order a flexible liner kit or full twinwall flue system from us, it will come with the suitable adaptor to connect to the 5" or 6" enamel pipe. That applies to most solid fuel appliances. The exception is for DEFRA Approved stoves, which have a 5" (130 mm) flue outlet. They can legally be used with a 5" (130 mm) chimney liner or full flue system as they produce fewer smoke particles than other stoves.

For more information, please see our blog about flue regulations

Note: All installations are to be carried out according to UK Building Regulations, Document J. The tips on this page are meant to help you to do so, but in no way should be considered as a replacement for the instructions and rules of Document J.