Building Regulations that apply to stoves

The following page is a brief description of the building regulations that apply to chimneys, flues and stoves. They are not intended to be a complete explanation and if in doubt reference should be made to ‘The Building Regulations 2000 Approved Document J Combustion Appliances and Fuel Storage Systems 2010 Edition’ or the building control department of your local council. 

Approved Document J is a PDF that you can view by clicking below:

Document J Building Regulations

Please note that Document J was updated as of October 1st 2010. The big changes are that a CO Alarm is now a requirement, the recommendations covering room ventilation have been altered and added to, Defra Exempt stoves can now be connected to a 125mm chimney if they have a 125mm outlet, pellet stoves can be connected to 100mm chimney as long as the chimney is of the right type.

Approved Document J of The Building Regulations stipulates that any work that affects an existing chimney (i.e. fitting a new stove or liner) or creating a new chimney now comes under building control.

An existing chimney or a new flue or chimney installation must be given a visual inspection to check that it is in good order, clear of obstructions and is of a suitable size and type for the appliance you plan to install. It may be necessary to sweep the flue (which should always be done anyway before fitting a stove or lining a chimney) and also, if necessary, to do a smoke test to check for gas tightness.


Stove flue sizes

The flue size (diameter or cross sectional area) must not be smaller than the size of the stove outlet.

It is in the building regulation guidance notes that the minimum flue size for stoves is as follows:

  • Up to 20kW burning smokeless fuel – Minimum 125mm diameter.
  • Up to 30kW burning any fuel – Minimum 150mm diameter.


If the stove is Defra Exempt and has a 125mm outlet then a 125mm diameter flue may be used. This is a recent update (Oct 1st 2010) to the regulations. So the regulations recommend a minimum flue size of 150mm for any stove (on which wood could be burnt) unless it is Defra Exempt. Many stoves come with a 125mm flue outlet which then requires upsizing to 150mm (unless Defra Exempt).