Ansell Chimneys

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Ansell Chimneys

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Full range of multi fuel and wood burning stoves

Building Regulations Information

Building Regulations - The Basics

Here are the most important and often asked questions surrounding building regulations regarding installation of a woodburner.

Building Regulations, Document J, Stove Installation Guidelines:

All stove installations now come under building control, the following will give the basics for stove requirements. It is 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 2002 Edition' or the building control department of your local council.

The 2002 edition of Approved Document J of The Building Regulations stipulates that any work that affects an existing chimney (ie fitting a new stove or liner) or creating a new chimney now comes under building control.

All woodburning and multi-fuel stoves require a class 1 Chimney. Existing Chimneys can be used but they should be checked for air tightness and the correct diameter for the appliance to be used.

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.

Failing Chimneys can be relined using a number of methods, one of the easiest methods is using a class 1 904/904 grade stainless steel liner. It is important that visual inspection must be made to ensure that the flue is not in close proximity to combustibles.

A permanent notice/data plate should be fixed at an appropriate position giving details of the location of the fireplace, the type and size of the flue and type of heating appliance used.

Please Note: A new revision of the Building Regulations is now available and must be followed as of 1st October 2010.

The main changes to the regulations are as follows:

  • From the 1st October 2010 you must install a battery powered Carbon Monoxide Detector into the room where the Stove has been installed. Without this the HETAS installer will not sign off your installation.
  • PLEASE NOTE: The Detector must have a sealed long life battery. You cannot install a standard Detector that has replaceable batteries.
  • Previously any stove under 5kw did not require an air vent. As from 1st October 2010 the rules have changed slightly. If your house was built on or after 1992 you would require an airvent, regardless of the output of the stove. This is due to houses becoming more and more insulated and less draughty therefore the need for replacement air into the room is required.
  • When you install a woodburning or multifuel stove the regulations state that you must step up to a 6" flexible liner if you purchase a stove with a 5" flue outlet. This rule is staying the same EXCEPT for stoves that are Defra Smoke Control Approved. If you purchase a Defra approved stove then can now install a 5" flexible liner. If your stove is not Defra approved you must increase to 6" as always.

Flues To Combustible Materials:

Any single skin flue pipe used must not come closer to combustibles than three times its diameter e.g for a 6"or 150mm pipe it needs to be a minimum of 18" 450mm from a combustible material. This distance can be reduced to 50mm if our double skin insulated flues are used.

Hearth Requirements:

A stove must stand on a non-combustible hearth extending a minimum of 225mm in front & 150mm out from the stove at the sides. If the hearth is on a combustible floor it must be at least 250mm thick. Some stove manufactures have models that have been designed and tested to have a hearth temperature not exceeding 100 degrees centigrade, in this case a 12mm hearth can be used.

Please Note: that if you using an appliance that is designed to run with the doors open then you must have at least 300mm in front of the stove.

As we previously mentioned that the hearth must be at least 250mm thick (unless the stove is approved for 12mm hearth) if you are installing the hearth onto a non combustible floor e.g concrete floor then the overall thickness can be 250mm. For example if the non combustible floor is made from 100mm of concrete then you have a slate hearth of 150mm to make up the 250mm required.

Hearths For Freestanding Stoves:

If you are planning to install a stove into a room with no standard chimney then you must ensure that your hearth is an minimum of 840mm x 840mm. While this is a minimum if you have a large stove you must still follow the rules as stated earlier e.g 150mm each side of stove and 225 in front.


Stoves use air from within the room for combustion. Any solid fuel stove which has an output higher than 5kws requires a permanently open vent with a cross sectional area of at least 550 mm² for every kW above 5kW.

When installing an permanent air vent it must be non adjustable and ventilators should be installed to ensure the occupants are not provoked into blocking the air vents up to stop noise and draughts.

Air vents should not be installed into a fireplace recess except on the basis of specialist help. If you install a mesh or other type of guard to stop pests getting into the house then the mesh must be no smaller than 5mm.

Where to position a permanent airvent:

You can install a permanent air vent anywhere in the room as long as it has direct ventilation to the outside.

What vent system is best?

A Ventilator is a ventilation system that you install using a 5" core drill to provide a permanent air supply to the room if you have a stove of over 5kw.

The Ventilator Also known as a Black Hole Ventilator has a system that uses a baffle to reduce draughts and to help reduce noise.

Flue Heights:

When installing a twin wall double insulated chimney system you need to ensure that the chimney height is compliant with the building regulations.

Below is a guide to the clearances you must have in order to comply.

The Flue must clear the roof by the distances laid out below to ensure that you receive a good draw on the chimney. Flue gases must be able to flow from the chimney freely in order not to cause any risks to the property.

A chimney that does not have the height laid out below could suffer from a downdraught problem resulting in the flue gases not escaping freely and causing problems.

If you come out through a roof and you are within 600mm of the highest point of the roof then you must clear the roof by 600mm. If you are coming out further down the roof level and more than 600mm then you must extend the chimney up a minimum of 1 meter and you must keep going until you either clear the highest point or you create a horizontal distance from the tiles of 2.3 Meters.

Why not call Ansell Chimneys now for a free quote

If you would like to know more or are interested in a quote we would be happy to help. Phone us on 01923 661 614, email us at or fill in our enquiry form and we will be in touch as soon as possible.