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 so comes under the Building Regulations.  

The Government issue an Approved Document which contains practical guidance on ways of complying with the Requirements of the Building Regulations which deals with Combustion Appliances. In the UK Document J building regulations apply to flues and chimneys. It is important that these are adhered to for safety and legality.
Building regulations

Fitting a  flue liner / chimney system yourself

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, 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 relevent Competent Persons schemes such as HETAS then they can sign off their work and provide you with a certificate.

Planning permission

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 propety 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 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, piece of mind of having a sealed system top to bottom, reduced risk of 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 prior to installing any chimney (unless you are approved to self certify, such as HETAS engineers).

Hearth requirements

A hearth provides a non combustible area for your stove or fire to sit on.

The purpose of a hearth is to protect combustible materials in the surrounding area (for example, carpets and floorboards) from heat, burning fuel and hot debris.

A hearth must extend a minimum of 300 mm (12 inches) in front of the fire or stove and 150 mm (6 inches) to the side of the fire or stove. The regulations also require the hearth to be set at a different level than the surrounding floor space to clearly define and mark the safe area. This can easily be done as the hearth can be set at a higher level than the surrounding floor level.

If a stove has been tested and shown not to raise the upper surface of the hearth to a 100 degrees and over, then the stove can be placed upon a non combustible hearth or stove plate with a minimal thickness of 12 mm. 

Marble, stone, granite, slate and tiled hearths are recommended hearth materials, glass or resin floor plates can also be used. 

If a stove is untested or is found to raise the hearth temperature to 100 degrees or more the hearth needs to at least 250 mm (9. 8 inches) thick. This is also the required thickness if the fire in question is an open fire and if the hearth sits on a bed of combustible materials (such as carpets or floorboards). Alternatively, the hearth may be 125 mm (5 inches) thick if there is a 50 mm (2 inches) air gap between the non combustible hearth and the combustible materials.

If the hearth is to be sited on a non-combustible floor such as concrete slab the total depth of the floor and hearth must be a minimum of 250 mm (9.8 inches), or if there is a 50 mm air gap beneath the hearth, 125 mm is sufficient.

Please note for free standing appliances (stoves and fires that are not fitted to an existing fireplace or chimney) the minimum hearth size should measure 840 mm by 840 mm (33.07 inches). There must still be a clearance of 150 mm from the sides and rear of the stove to the edges of the hearth. It is recommended that the hearth extends a minimum of 300 mm (12 inches) in front of the stove/fire. However if an appliance is only able to be used with the doors closed (which is unlikely) the hearth would only need to extend 225 mm from the front of the appliance. For large stoves this means that the hearth will need to be in excess of 840 mm by 840 mm. 

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 less smoke particles than other stoves.

Room ventilation

Normally for most houses in the UK no extra ventilation is required when installing a stove rated at 5kW or less. For stoves above 5 kW a permanent air vent connected to the outside is required in the same room as the appliance. The size of the vent would normally need to be a minimum of 550mm² per kW above 5 kW. e.g. a stove rated at 7kW would need 550mm² x 2 = 1100mm². That would be a square opening approx 33mm x 33mm.

The purpose of providing extra ventilation for larger stoves is simply to ensure there is enough oxygen being supplied into the room to allow proper combustion in the stove.

Note: The requirements regarding ventilation have been updated in the most recent version of the Regulations and are now based on the air permeability of the house. Houses built after 2008 should have an air permeability test result which you should be able to see at the time of purchase. In practical terms what is likely is that the newest houses will be very air tight, i.e. no gaps under doors etc., and so will have a greater requirement for extra ventillation. If the test result shows an air permeability of less than 5m³/h.m² then in these cases the requirement is 550mm² per kW, regardless of the total kW output of the stove. If in doubt please ask us for advice and we'll do our best to help. It is unlikely that a property built before 2008 will have an air permeability less than that so the normal procedure will apply to 99% of properties i.e. only stoves greater than 5kW need a vent. 

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