Building Regulations and Manufacturers Instructions

Calvin May, Technical Standards Manager on dealing with conflicts between Approved Documents/British Standards requirements & manufacturer instructions

In last year’s Technical Bulletin 19, HETAS covered the subject of application of Approved Document guidance and BSI recognised standards to comply with the principal requirements of the UK Building Regulations J1-J5.

The article included reference to the considerations of guidance working alongside installation practices contained within manufacturer installation and operating instructions, however queries continue to arise on the official position surrounding any conflicts that are experienced between Approved Documents/British Standard requirements and guidance stipulated within appliance/chimney manufacturer installation instructions.

As the industry recognised safety organisation for the design, installation and commissioning of solid fuel appliances and associated products, HETAS always encourages its installers to undertake a risk-based approach towards building works involving solid fuel equipment, ensuring reference to prescribed guidance within approved documents and British Standards is utilised in support. It is essentially the persons carrying out the building work who are responsible in ensuring the work is carried out safely and complies with the Building Regulations requirements, so any assessment should be done to ensure that the appliance is installed in such a way that it operates effectively and safely. 

For these reasons above, in instances whereby conflict between Approved Documents/British Standards requirements and manufacturer instructions exist, it is the position of HETAS that the most stringent guidance between documents shall apply.

The reasons for this are simple in that UK Building Regulation approved documents are written specifically for the national member state in which they are used (i.e., Approved Document J – England & Wales, Scottish Technical Handbook – Scotland), meaning they can be better tailored for compliance against the relevant practices and legislation within UK law. These include the practicalities for the types of building an appliance is being installed into, which may have differing insulation, ventilation and construction properties based on their own national requirements.

The importance of these documents is highlighted further by guidance being fully supported by years of independent industry research and developments, going as far back as the first release of Approved Document J back in 1966.

Manufacturers Instructions

Appliance manufacturer installation instructions, although comprehensive, may have been designed and written in such a way to cover export and sale in a varying number of European and/or international member states, most of which are likely to have differing national requirements to comply with the country’s local legislation.

An example of this relates to the minimum internal measurement size of a chimney, which for the UK can be reduced to 125mm if the appliance has been verified as meeting the conditions of appliance exemption under the Clean Air Act:1993. The Clean Air Act is a piece of UK legislation, and other national member countries are likely to have differing minimum flue diameter sizes dependent on the country of install and national legislation which covers them.

With this in mind, appliance manufacturer instructions still play an important part during the design and installation of a solid fuel appliance. For the reasons stated above, some appliance manufacturers do prescribe installation practice above and beyond those written into UK approved documents, and it is therefore important that if the manufacturer prescribes more stringent guidance, then these caveats shall be followed as part of the installation and commissioning of the appliance.

For example, appliance manufacturers may prescribe greater hearth distances in front or to the side of an appliance, greater than the 225mm distance referenced in ADJ for closed roomheaters, which is based on a standardised appliance design. This may be a consequence of the design of the appliance, which may include larger style, extended or non-standard combustion doors, and additional hearth distance is required in front of the appliance to ensure that during the operation of the appliance the risk of ash or fuel falling from the appliance and coming into contact with combustible materials is significantly reduced, or the radiant heat from the fire-bed does not damage combustible flooring if placed too close to the front of the appliance.

As part of any solid fuel installation, it is therefore important that both approved documents and British standard requirements are considered, alongside guidance within both the appliance and chimney manufacturer installation instructions.

Copies of manufacturer installation instructions for HETAS approved appliances are available on the HETAS website at:

For further information on the application of industry guidance to comply with UK Building Regulations can be obtained by contacting the HETAS Technical Helpline at or 01684 278170, Option 1. Please have your HETAS registration details available when contacting the HETAS Technical Helpline.

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