Types of chimney liner

Types of chimney liner.

Many people are becoming more aware of the benefits of lining their chimney when installing a solid fuel appliance, but which flexible liner is right for you?

Gas and oil liner

Gas and oil liner has a lower tolerance to heat than solid fuel liner, It is often made from a single wall from either aluminium or 316 grade stainless steel. This grade of flexible liner is not suitable for using with a solid fuel appliance.

316 Grade twin skin

This grade of stainless steel liner is classified as a class 1 liner and is suitable for gas, oil and multifuel, including wood burning appliances with maximum flue temperatures of around 500deg C. It is manufactured using two layers of steel folded together to create a smooth inside wall to prevent friction and a tough outer wall for protection.

316/904 Grade twin skin

As with the 316 grade this liner is suitable for solid fuel appliances and is the most economical for burning smokeless fuels. The inner layer is made from a 904 grade stainless steel for protection against the fumes created by the combustion of  smokeless fuel. While the outer layer is made from a 316 grade shell for protection.

904 Grade twin skin

Manufactured in the same way as 316 grade but with a 904 grade steel inside and out, This liner is the best you can buy and is recommended when burning mostly smokeless fuels, for heavy usage and if you are slumbering the stove overnight.

Flexible liners usually come with a guarantee from the manufacturer for 10, 15 and 25 years depending on the grade of steel, however it is always a good idea to read the small print as many impose conditions relating to insulating the chimney or only using only the manufacturers components on the installation .

If you live in the Holyhead, Conwy, Denbighshire, Flintshire, Cheshire, Wrexham or Wirral areas and are considering installing a stove call North Wales Stoves on 01745 822344 or email us 

You don't need a chimney to enjoy a solid fuel stove.

One of the fantastic benefits of having a solid fuel stove is that it can be adapted to pretty much any situation. Unlike other types of heater which may need to be piped or plugged in solid fuel is an independent source of heat.


Even if you have no exsisting chimney, a solid fuel stove can be installed with little fuss using an insulated flue to create a class 1 chimney system almost anywhere.


Insulated flue, also known as double skin and twin wall flue or factory made metal chimneys are produced by using a layer of insulation sandwiched between two pieces of metal pipe.


This means that the flue gasses can keep warm whilst travelling away from the appliance meaning they stay as a gas and float off. 
Cooled flue gasses (below 100deg) become solid and can settle along the flue way causing a flammable tar like build up which can create a blockage in the flue and prevent further gasses leaving the appliance safely.


Traditional single skin flue does not have these insulating properties and loses heat quickly. A chimney needs to be warm to draw the gasses away. 
Double skin flue also remains cooler on the outside meaning it can safely pass through walls and celings without causing a risk of fire once it starts to get warmed up.


There are many insulated flue manufacturers but unlike a single skin vitreous enamel flue which is usually a universal fit, Insulated flues are usually made to fit only the manufacturers own components, therefore it is important to be aware of the brand you buy in case you need any replacement parts or additional parts along the way. 


There are various ways in which the pipes can connect together depending on the manufacturer, some are twist lock, others are push fit but in most cases each length is locked to the next with an additional locking band for extra safety. The internal diameter or insulate flue pipe is usually 2" smaller than the external.


The pipes will need 50mm spacing around them from combustiable materials, should be boxed in if passing through cupboards etc. so that things cannot be leaned against them by accident and to be supported every 2mtrs either internally with appropriate floor and celing plates or externally with brackets to take the weight.


In cases where it is not possible to acheive the recommended 4.5mtr height for a chimney there are additional fans that can be added to help with draw if this cannot be acheived naturally.


If you are thinking of installing a stove and need advice on the correct flues to use why not give us a call on 01745 822344 or email us 

Building Regulations and legal requirements.

Building regulations in England and Wales apply to most new buildings and also any alterations to exsisting buildings. 


They are used to control methods and materials used in construction, fire protection and the operation, safety and efficiency of services within the building.


The same buiding regulations do not apply to every country and there are a seperate set of rules in Scotland and Northern Ireland.


This article addresses the requirements for new and replacement solid fuel systems in exsisting or extended dwellings. It discusses in a basic way what is and is not permitted under current building regulations in England and Wales.  
It is not an installation guide. We recommend that anyone wishing to install a solid fuel appliance contact a HETAS registered competent person for advice. If you are in North Wales, Wirral or Cheshire we can offer this service, call us on 01745 822344. 


Approved Document J provides guidance and sets out the requirements in respect to installation of a solid fuel appliance.
From this document you can find guidance on the construction and size of the hearth, Details of the chimney dimensions, position and construction and also methods for testing.
It advises ventilation requirements, advice on proximity of combustiable materials to an installation and also advice on notice plates and how these should be fitted and where they should be located. 


There is no regulation that requires you to line an exsisting chimney. 
However, a competent installer of any appliance needs to be sure that the chimney is free from defects and suitable for it's intended use. 
If any work undertaken on the chimney (which includes a new liner) is done in conjunction with installing a heating appliance then that work falls under a controlled service and therefore must be carried out by a competent person OR approved by your local area building control. Also any alteration to a fireplace which changes the fuel it uses e.g. changing from gas to solid fuel is also subject to building regulations.

Choosing a central heating and hot water system.

Regulations govern the type of heating and hot water systems that may be put into new  dwellings or as replacement in existing ones.
This is to create the most energy and carbon efficient installation possible. 
So choosing the correct system and also fuel is very important.
With new buildings there are complex calculations to be made to make sure they reach carbon emissions targets.


Wood fuel is generally accepted as carbon nutural, so choosing a woodburning stove for a new house will allow for more flexibility with other enegy and carbon saving elements.
Solid mineral fuels have a higher carbon content and you may have to compenstae elsewhere if you consider a system of this type.

Efficiency of a stove

All solid fuel appliances must meet minimum requirements for efficiency. This is specified in part L of building regulations. All HETAS approved appliances conform to these requirements.


When looking for appliance efficiencies and comparing be aware that some efficiences quoted in manufacturers literature will list 'net' others are dispalyed as 'gross'. HETAS lists an appliances gross efficiency and in a HETAS showroom such as North Wales Stoves Ltd you will be able to find the gross efficency of each appliance displayed for easy comparrison. 
As a guide to convert net to gross you can use the following sum. 
For woodburning stoves. net x 0.91 =gross
For Multifuel stoves. net x0.98 =gross
Appliances that have not been approved by HETAS may also be suitable but this must be verified by your installer prior to installation.

Replacing an existing appliance. 

When replacing any heating appliance, the new one should be more efficient with its carbon emissions than the old one. This does not have to mean the appliance efficiency is higher as the fuel type is also an important factor and may offset a reduction in appliance efficiency.

Thinking of installing a solid fuel applaince?

In England and Wales there are two ways in whiuch this can be acheived legally.
1. Use a competent person. such as a HETAS engineer. They will certify their work, fit in accordance to building control and take care of the required paperwork. 
2. DIY fit with the guidance of your local building control. Building control consent is required prior to installation or replacement of a solid fuel appliance and also once the installtion is complete. A building control inspector will visit the installation and decide if it is safe for use.

Smoke control?

If you live under a smoke controlled area then your solid fuel heating appliance must meet the following criteria:


You must use either an 'exempt' appliance.(using only the fuel specified in the appliance instructions, information is also listed on the DEFRA website.)


Or use an authorised smokeless fuel. 


Failure to adhere to these guidelines can lead to a £1000 fine for each offence.


To check if you live in a smoke control zone visit the DEFRA website.

Who makes legislation regarding smoke control zones? 

The governmemnt has the power to authorise smokeless fuels and exempt appliances in England. 
With Scotland and Wales the power rests with the ministers in ther respective parliaments. In Northern Ireland clean air order 1981 applies.


Stoves that are not an 'exempt' appliance  that are used in a smoke control zone can use an authorised smokeless fuel. 
A popular choice is anthracite which is high in carbon and low in volatile matter. You can find a list of authorised smokeless fuels on the DEFRA website.
Exempt appliances are tested to show they meet DEFRA's smoke control standards for emissions when they burn non authorised smokeless fuels such as wood. Firewood is not an authorised smokeless fuel and is only permitted for burining in a smoke control zone on an exempt appliance that has been exempted for wood burning.


Wet wood which has not been seasoned will burn ineficciently with lots of smoke. Seasoned wood or kiln dried wood will burn with minimal smoke. Wood should have a moisture content less than 25% to burn effectively.
In an exemption notice on an appliance it may state that the wood must be seasoned or even specify a maximum moisture content. 


North Wales Stoves Ltd is a HETAS registered retailer and can provide advice and information on suitable appliances and the parts required for a DIY installation or we can arrange a full installation with a HETAS Registered competent person in and around North Wales. Areas covered include Conwy, Anglesey, Denbighshire, Flintshire, Wrexham, Cheshire and Wirral. Call us on 01745 822344 to arrange a survey.

What is Chimney Lining?

A Chimney is made to safely remove the smoke from a fireplace or stove to the outside of a building, without causing danger to the people who live there.


A chimney works well because hot air rises and moves from high to low pressure. 


Chimney gasses need to remain hot so that they can stay as a gas and rise. 
Things like running a stove at a very slow rate or cold air leaking into the flue will cool the gases and this will affect how the chimney performs. 


Flexible liner and other methods of lining chimneys are designed to replace the flue in an existing chimney, The diameter of liner used will depend on the requirements of the appliance.


You may add insulation or this might be already intergrated into a flue system to improve the efficiency of the draught. This is a particular requirement for external situations. 


There are various methods and materials suitable for lining chimneys.


Chimneys with existing flues can be relined in several different ways. These 
include:


1.  Using rigid sections of clay, pumice or refractory liner installed by cutting 
into the chimney wall or by lowering sections down from the top of the 
stack and infilling with an insulating material.


2.  Insulating concrete, pumped in and around an inflatable former by a 
specialist contractor.


3.  Stainless steel flexible liner in a continuous length lowered down the 
chimney.


4.   Spray on coating by a specialist contractor.


5.   Ceramic coating by a specialist contractor.


The suitability of any of these methods of lining is dependent on each 
individual system. You should seek professional advice on what is the most 
appropriate solution for your need.




Why Line Chimneys?


Chimneys should be lined for a number of safety related reasons. 

New chimneys may require relining depending on the suitability of the current system, However systems built before 1965 will usually require a modern lining solution for the following reasons:


1. The flue walls may have broken down and can leak smoke into the room or other parts of the building, or if terraced or semi detached into the next building.


2.  Condensates or tar can seep through chimney walls causing staining, inside or outside of the building.


3. Lining with added insulation improves the operation of appliance and flue (particularity important when the chimney is on an external wall). Because flue gasses must be warm to rise.

4. Old flue systems may be worn and rough. This can cause frictional resistance to the flow of the gases resulting in poor updraught.


5. Large flues (over 200mm) particularly ones containing voids may affect appliance performance as gasses may cool and set before they can be expelled from the void.


It is important to follow the manufacturers advice on the correct size of flue to use with your appliance.


Before having a liner installed in your chimney,you should have it swept to remove soot and tar deposits by a professional chimney sweep. 


For those that already have a chimney lining, a competent sweep will be able to inspect for the following faults:


1.   Liners fitted the wrong way up
2.   Out of line or overlapping liner
3.   Obstructive ledges hindering updraught
4.   Protruding cement at joints
5.   Liner removed during previous service work or installation
6.   Damage through incorrect sweeping 
7.   Masonry damaging the liner
8.   Blocked terminal (cowl or rain cap)


These faults can lead to a number of problems with the operation of a solid fuel appliance. 


More importantly, faults with chimney lining can pose a risk to the safety of everyone in the house and should be rectified immediately.


Safety First! Always ensure that you have a working carbon monoxide detector fitted in any room where a solid fuel applince is installed and that you test this regularly.


For a HETAS registered stove installation service, advice on your stove and chimney requirements or to book a free stove installation survey throughout Cheshire, Wirral and North Wales including Anglesey, Conwy, Denbighshire, Flintshire, Mold,Wrexham and surrounding areas call us on 01745 822344. or email northwalesstovesltd@gmail.com