Stephen Shepherd, HETAS Technical Helpline Advisor, discusses how to achieve chimney termination compliance.
With increasing consumer and public awareness relating to air quality improvements and smoke emissions from burning wood and mineral fuels, HETAS offer guidance on the correct siting and termination of chimneys when considering neighbouring or adjoining properties.
In order to clarify our position, this technical article serves to remind installers of the importance of achieving chimney termination compliance in accordance with Approved Document J, diagram 17.
These guidelines are well established to provide a presumption of compliance for the majority of cases so that the products of combustion are discharged safely to atmosphere above roof level and above any low-pressure zones which may occur from dependent wind effects.
However, the presumption of following guidance does not always guarantee compliance and in some cases, you may need to provide additional solutions if products of combustion are not being discharged effectively.
England and Wales
Town and Country Planning (General Permitted Development) Order 1995 and subsequent amendments allow local authority planning departments in England and Wales to grant certain permitted developments. This means in a lot of cases, chimneys can be erected to the rear and sides of a property without the need for this work to be formally approved by planning consent by the local authority, as long as the work is compliant, notified by either a competent person scheme or directly through Building Control.
The diagrams below depict how to achieve compliance in this situation.
Chimney Termination – roof view
However there are certain situations where these requirements may apply for chimney termination. Twin wall system chimneys being erected in sensitive conservation areas for example (i.e. Peak District, Lake District, New Forest etc.), listed buildings or commercial properties where planning consent would need to be applied for.
Local Authorities are permitted to accept Notifications from installers Registered with approved Competent Person Schemes; however they can still intervene should compliance not be achieved. It is therefore important to follow Guidance in Approved Document J and achieve compliance first time. Local Authorities hold Enforcement powers and can exercise these against installers and consumers.
In addition, it is imperative that the end user is fully aware of the correct use of fuels, its moisture content and how to correctly store the fuel and the way that their appliance must be operated in order to achieve effective combustion of the fuel without promoting excessive smoke, as this in some cases can add to nuisance queries.
Roof topography to the rear and sides of properties can be complex in nature; making it difficult to interpret chimney termination height and distance without a measurement taking place.
Achieving compliance is essential to avoid neighbour challenges for the installation methods with the local authority.
Single storey rear extensions and conservatories are in our view one of the most difficult locations to site a chimney; for example, roof Velux, height & proximity to adjoining or neighbouring properties can be an issue. Approved Document J suggests chimney height should be at least 4.5m to achieve a good flue draught, however, single storey extensions rarely achieve this height. To mitigate this, we recommend the installer undertakes an appropriate flue calculation to BS EN 13384, to ensure the shortening of the flue below the 4.5m prescribed within approved guidance does not have a detrimental effect on the flue draught of the installation, which will allow products of combustion to be dispersed appropriately. It is also advisable to install a DEFRA exempt appliance, as these have been appropriately designed so that they do not emit excessive smoke when burning the appropriate fuel. Chimney termination should always comply with Approved Document J, Diagram 17. Chimneys which cross a property boundary are always classed as trespass, and permission should always be sought by the consumer/installer from the neighbouring property before installation works commence and to ensure no future boundary issues arise.
Contact the HETAS Technical Helpine on 01684 278194 or email firstname.lastname@example.org.
Additional technical support can be found in the Technical Area of the HETAS website (login required).