Flue FAQs and Flue Installation Advice

What is Twin Wall Flue?

Twin wall insulated flues are stainless steel system chimneys which consist of two stainless steel metal walls with insulation filling the space between them. Our Twin Wall Flue Systems offer a longer life than most and come with a lifetime warranty (lifetime of the stove). Factory made system chimneys are easy to handle and available with a wide range of fittings such as elbows, terminals and tees, all of which simply push fit together and then are locked together with a locking band. They are easily assembled and supported with purpose designed support brackets. Flue Direct's Twin Walled Flue products, can be used internally and externally and are certified to BS EN 1856-1:2009.

Stainless steel chimney systems tend to be used in existing buildings that do not have a chimney stack and inside extensions, because they do not require a dedicated foundation and can be easily retrofitted and enabling a wood burning stove to be fitted almost anywhere.  Click HERE for Flue Direct's Twin wall Flue system range.

How to Fit a Flexible Flue Liner - FAQs and Installation Advice

Q: Installing a wood burning stove in a masonry chimney stack

A: Below is a general guide to the components commonly used for a wood burning stove installation in a fireplace with a masonry or stove chimney stack. We'll start at the stove end and work upwards:-

Generally, you will need to use vitreous enamel stove pipe from the stove to the stack itself. This is available with or without access doors for sweeping purposes. Many stoves can be swept through the stove by removing the internal baffle plate at the top of the burner. Once you reach the stack itself, you need to decide if you need to line the chimney with a chimney liner or not. Also, if you are to line the stack, then you need to know the diameter of chimney liner you'll need. You'll need an adaptor to connect between the vitreous enamel stove pipe and the chimney liner. These are available as a standard adaptor or as an increasing adaptor if the liner is a larger diameter than the vitreous pipe.

Don't forget to order a nose cone. The nose cone is used during installation and then discarded. Attached to the leading end of the chimney liner it helps prevent snagging against the side of the stack and also provides a draw cord from which the liner can be guided down. Please note that not all manufacturers provide draw cords, so you may need to supply your own (nylon string and a washer). You'll need to close off the bottom end of the chimney stack. You can do this by using one of our register plates, together with a register plate adaptor. At the top end of the installation, there are various configurations for supporting the liner.

How to Fit a Flexible Flue Liner

FLUE FITTING PREPARATION

All installation work should be carried out by a fully qualified HETAS approved engineer. Before starting work, read the installation instructions carefully supplied with the products. Good working practices and statutory health and safety considerations should be followed. Safe workingplatforms or other means of access should be arranged to avoid accidents. Wear protective gloves, goggles and dust-masks, particularly when handling insulation, and dusty or sooty materials. There is a danger of cuts and abrasions from the liner and metal fittings.

PREPARING THE CHIMNEY

Check that the appliance and chimney arrangements are satisfactory and that the walls of the chimney are at least 100mm thick solid masonry; ensure that the chimney is structurally sound, wind proof and watertight. Clean the chimney using a brush and rods. Remove any terminals or cappings, which might effect installation of the liner.

There are two methods of installation at the top of the stack that we recommend (1) where the pot is removed to secure the liner or (2) a pot hanger or pot-hanging cowl is used therefore removal of the pot is not required – this is not recommended in an exposed area.

METHOD (1) - POT REMOVAL

1. Attach the draw-cord to the nose cone. Use self- tapping screws OR strong tape to secure the nose cone to the end of the liner. Lower it into the chimney from the top, if necessary gently pulling from below using the draw-cord. When the lower end position has been determined remove the cone
2. Remove the chimney pot and clear any cement and debris from the pot area.
3. When the chimney liner is all the way through the flue, connect the base of the chimney liner to the appropriate adaptor using stainless steel screws and seal with fire cement.
4. If you insulating the chimney do this now (see Insulation).
5. Cut the liner to the desired length leaving about 100mm for the clamp to be secured and insert the Protection Sleeve into the top of the liner.
6. Place the Top Plate over the liner and secure the liner in place using the Top Clamp. The clamp should secure both the liner and Protection Sleeve.
7. Flaunch the Top Plate and Top Clamp and surrounding area with a suitable mortar and re-fit the chimney pot.

METHOD (2) - NOT REMOVING POT

1. Attach the draw-cord to the nose cone. Use self- tapping screws OR strong tape to secure the nose cone to the end of the liner. Lower it into the chimney from the top, if necessary gently pulling from below using the draw-cord. When the lower end position has been determined remove the cone.
2. When the chimney liner is all the way through the flue, connect the base of the chimney liner to the appropriate adaptor using stainless steel screws and seal with fire cement.
3. If you insulating the chimney do this now (see Insulation).
4. Cut the liner to the desired length – this should be to the height of the chimney pot.
5. Attach the Pot Hanger or Pot Hanging Cowl to the top of the liner – the bottom spigot is inserted into the top of the liner. The straps are then tightened around the liner to form a secure hold.
6. The Pot Hanger or Pot Hanging Cowl should now fit flush with the top of the chimney pot.
7. If the Hanger has a strap on the outside secure this to the pot.

FLUE LINING TO APPLIANCE CONNECTION

At the bottom of the chimney, secure the liner into the socket of an appliance adaptor (MA Adaptor (20-DMA) using fire cement. For open fires, secure and seal a flue gather into the masonry gather above the fire opening. For other appliances use a minimum 600mm length of flue pipe before connecting to the appliance adaptor. Please note that the liner should be the at least the same diameter as the outlet from the appliance.

The space between the liner and the inside wall of the chimney should be sealed. A Chimney Notice Plate should be filled in and fixed in an appropriate place as per Building Regulations.

INSULATION

We recommend insulation or back filling only on tall, large or exposed chimneys. Whilst not essential, an insulated flue should ensure maximum performance and minimize condensation in the lining.

To insulate the chimney either:

1. Use a loose fill granular insulating material such as Micafil, this should be mixed one part ordinary Portland cement to six parts Micafil.
2. Rockwool insulating tubes.

CUTTING THE FLUE LINER

We recommend cutting the liner with a hacksaw, be sure to use protective gloves while cutting because the liner can have razor sharp edges.

Talk to one of our Technicians today for advice and information on all the components you will need for your flexible flue liner installation.

Typical Log Burner installation inside a chimney void requires:

• Vitreous flue pipe length (with or without access door)
• Vitreous to liner adaptor (MA Adaptor) or a vitreous to liner increasing adapter (MR Adaptor)
• Flue liner
• Top plate, Clamp and rain cap OR simply use a pot hanging cowl
• Nose cone

Q: What diameter multi fuel flue liner do I need?

A: The diameter of the chimney liner required depends on many things including the type of appliance and fuel/s which you are using, current building regulations, the fireplace opening size and the chimney stack height.

We'll start with chimney liners for multi fuel stoves as this is fairly straightforward. By multi fuel we mean any or all of the following fuels; cured dry logs, coal, coke, peat and smokeless fuel.

The diameter of the chimney liner will normally be the same diameter as the outlet from the stove. An average sized multi fuel stove will have a 6" (150mm) diameter outlet and the chimney liner and stove pipe will nearly always be 6" (150mm). There is an exception to this rule as follows:-

Building regulations state that if you are burning cured dry logs only, then the minimum diameter for a chimney liner should be 6" (150mm). So if the outlet from your stove is 5" (125mm) and you burn only wood, then you'll need to increase to 6" diameter chimney liner. This can either be achieved directly from the stove with an increaser in vitreous enamel stove pipe, or you can use 5" diameter stove pipe and then use an increaser liner to pipe to connect to the liner.

Can I Have a Stove or Wood burner if I Don't Have a Chimney? Yes You Can! Are you wondering 'Do you need a chimney for a log burner?' Your property does NOT need to have a chimney stack, you can use a manufactured flue system called twin wall insulated flue instead to take away the flue gases from your stove.  You can find our range of black and stainless twin wall flue available to buy here.

How is a Wood Burning Stove Installed Using Twin Wall Flue? When installing a twin wall flue system there are two options: An Internal Flue System; or an External Flue System. Which type of flue route will depend on where the stove is going, what is your preference in terms of seeing the flue inside or outside, if there if room for the flue to run inside and most importantly ensuring the chosen flue route complies to HETAS guidelines and Building Regulations.  Both options can be done using twin wall flue and you may need to consider if you have a top or rear exit from your stove too. You can run the twin wall flue in either or a combination of black or plain stainless twin wall flue depending on you preference for aestheitics and cost (Black twin wall flue is slightly more expensive).

What Flue Do I Need When I Don't Have a Chimney? When there is no existing chimney you will need a Twin wall Flue system. When you've decided on where you want to install your stove and where you want the flue route to run i.e either an internal twin wall flue system or an external twin wall flue system then you can see further links below with all the flue supplies you will need. Please note: This is just a guide and you will need to check for yourself that the appropriate amounts of components relate to your building height as these are based on typical house / single story properties etc.

Can I install my stove and flue myself and then get it approved? Yes you can - It is a legal requirement to notify any solid fuel installation in England and Wales to the relevant Local Authority Building Control either via a Competent Person Scheme such as HETAS or directly to the council. An application would need to be made to your Local Authority Building Control prior to installation if you intend to carry out the work yourself or if your installer is not registered with a Competent Person Scheme that covers the installation of solid fuel appliances. A HETAS Registered Installer can only notify work they have carried out themselves. We strongly recommend the installation be carried out by a HETAS Registered Installer to ensure the installation is safe and complies with relevant Building Regulations.

Can any property have a wood burner / stove? Within reason, any property may be suitable whether there is an existing chimney or not. In most properties without an existing chimney, a system chimney may be installed as opposed to building a new masonry chimney. This may run within the property or externally providing it is safe to do so.

Buy Flue Direct's Twin wall Flue Installation Kits here.

Twin wall flue kits for your stove installation when you don't have a chimney - Available in 5" inch and 6" inch flue black and stainless.  Other diameters sizes also available.

How to Install Twin wall Flue for My Stove / Wood burner - Different Flue Route Options

Q: How should a twin wall multi-fuel flue system be installed at a house running internally and with a top outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please click here for fitting information.

Q: How should a twin wall multi-fuel flue system be installed at a house running internally and with a rear outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please Click here for fitting information.

Q: How should a twin wall multi-fuel flue system be installed at a house running externally and with a top outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please click here for fitting information.

Q: How should a twin wall multi-fuel flue system be installed at a house running externally and with a rear outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please click here for fitting information.

Q: How should a twin wall multi-fuel flue system be installed at a bungalow running internally and with a top outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please click here for fitting information.

Q: How should a twin wall multi-fuel flue system be installed at a bungalow running internally and with a rear outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please click here for fitting information.

Q: How should a twin wall multi-fuel flue system be installed at a bungalow running externally and with a top outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please click here for fitting information.

Q: How should a twin wall multi-fuel flue system be installed at a bungalow running externally and with a rear outlet from the appliance?

A: All installation work should be carried out by a fully qualified HETAS Engineer. Please click here for fitting information.

Why do I need to replace or reline my chimney? There will be one of three reasons why an existing chimney may need to be relined:

• If it is found to be unsound from the results of an appropriate test by a skilled engineer

• If the cross-sectional area of the flue is too large or small for the intended appliance

• Any of the existing lining is found to be unsuitable for the proposed appliance type When an appliance is replaced, Approved Document J states: if a chimney has been relined in the past using a metal lining system and the appliance is being replaced, the metal liner should also be replaced unless the metal liner can be proven to be recently installed and can be seen to be in good condition. Page 24, paragraph 1.39

Flue – Building Regulations. All work that affects an existing chimney which includes installation of a stove, flue liner or creates a new chimney is classed as building work and so falls within the remit of the building regulations department of the local authority. The government issue an approved document, which contains practical guidance on ways of complying with the requirements of the building regulations, which deal with combustion appliances. In the UK, Document J of the building regulations applies to flues and chimneys. These must be adhered to for safety and legality.

If you want to get a twin wall flue pipe fitted in the UK, then you don’t usually need planning permission under normal circumstances. The main exception here is if you have a listed property. Listed properties in the UK have a few different types (grades). For all listed properties, you’ll need permission for new flue pipework of any kind. If you want to fit the twin wall flue yourself in England and Wales, then you need to contact the local council planning department or building control and check the building regs. You need to tell them when you have completed the work so that they can come and inspect it. We recommend that you communicate heavily with the local council before you make all your decisions on your stove installation and double or even triple-check all the details. You really do not want to be getting headaches late on in the process of this. That will be expensive and time-consuming for you - much better to deal with details early in the planning stages when it is not stressful.

What is HETAS & HETAS Approved Flue. HETAS (Heating Equipment Testing and Approvals Scheme) is the only specialist organisation approving biomass and solid fuel heating appliances, fuels and services. This also includes the registration of competent retailers, installers, servicing engineers and chimney sweeps.  HETAS approved flue components have been tested to ensure they pass the correct safety levels and manufacture.  HETAS approved flue and stove installers have been trained to follow HETAS rules and regulations and passed a test of competence.

HETAS Flue & Stove Engineers. If you choose to hire a HETAS engineer to fit your flue and wood burner, they are certified to handle all the necessary regulations for twin wall flues on your behalf. However, if you require planning permission for the installation, it is important to consult with your local council. The council will be able to provide guidance on the specific planning requirements for your area and ensure that you comply with any regulations or restrictions that may apply.

When should I get my chimney swept? We recommend you have your chimney swept at least twice a year when burning wood and at least once a year when burning smokeless fuels. The best times to have your chimney swept are just before the start of the heating season and after your stove has not been used for a prolonged period. If sweeping twice a year, the second time should be after the peak of the main heating season.