From The Stovefitter's Manual by Julian Patrick

 If you don't have a chimney you will require a clip-together twin-wall system referred to in the trade as "twin wall".

If self-installing you can read our helpful Installing a Twin Wall Flue Chimney guide.

Everybody with no chimney might also find this guide to chimney regulations useful (short useful video included).

You can buy the individual components from us, or a bespoke designed twin wall system.

Need an installer? Our list of installers who will fit our flue systems.

Let’s see what a full time stove fitter or self installer must look at when surveying a property for the first time:

A stove fitter will almost always visit and survey your property prior to providing a quote/plan of action for installing a wood burning stove. You will already know your own property well and may also have already decided what your installation plans are. This area of the website is though of some importance and it is advised that you act like a stove fitter and conduct your own survey using the information provided.

One of the stove fitter’s firsts tasks will be to obtain your address. He needs this to find you of course… but he will also check to see if you are in a smoke controlled area. If you are not then he can relax a little. If you are in a smoke control area then he knows he must steer you towards ordering a stove approved by DEFRA if you wish to burn wood.

The first direction an engineer will usually look when he pulls up outside of your property is upwards: is there a chimney stack? If he cannot see a stack then he makes a mental note that he might soon be creating one – using high temperature (HT) twin wall flue pipe also known as double-skin flue pipe or stainless-steel flue pipe. We’ll come back to this shortly.

If there is a brick or stone chimney present he’ll be mentally calculating how high it is (the higher the chimney the better the performance of the stove although anything that will add 4.5m above the stove should be acceptable).

Does the chimney have a pot? Is the pot suitable? Does the top of the chimney pot have sufficient clearance, horizontally, from any roof surface, wall, obstacle?

If there is a chimney then his mind will also likely be thinking about how to fit a chimney liner: if he has to line the chimney with flexible flue liner (silver metal tube) can he use ladders or is this a scaffolding job, cherry picker maybe? Is the stack safe to climb on top of to fit the chimney liner?

This is all before he has knocked on your door.

Once inside the stove fitter will speak to the house owner and the situation will quickly become apparent: the householder does or does not have a chimney in the location where they want a wood burning stove installation.

In this case the stove fitter will be thinking various thoughts: Is the recess big enough for a wood burning stove installation and is it of a suitable construction? Is the hearth big enough for a stove installation and of a suitable construction for that stove? Are there any potential fire hazards present, in particular wooden beams/lintels?

He will likely shine a powerful torch up the chimney and decide if it requires the fitting of a flexible chimney liner, whether vermiculite chimney insulation is necessary and whether a liner will fit (5″ or 6″). He might decide that a chimney liner is not necessarily required although this is uncommon. He may also take notes on what flue materials and flue pipe will be necessary; the size of stove for the room. Is an air vent required? Is there an extractor fan in this or an adjoining room that might cause problems? He will speak with the householder about stove choice.

In this case the stove fitter will be wondering, if there is one, how big an original fireplace (builder’s opening) is behind the existing fire or wall surface for the wood burning/multifuel stove installation? He will be thinking about opening up this recess.

He will, if he has room (with open fires one often has enough room and sometimes electric fires can be easily removed) shine a powerful torch up the chimney and decide if the chimney requires lining with a chimney liner, whether vermiculite chimney insulation is required and whether a liner will fit? If not he will discuss this issue with the customer.

He might (rarely) decide a chimney liner is not necessarily required.

He will also take notes on what flue materials will be necessary; what size stove for the room; is an air vent required? Is there an extractor fan in this or an adjoining room that might cause problems?

He will speak with the householder about stove choice, hearth choice and the process of making good following the excavation of the recess.

Twin wall flue refers to the silver pipe you can see in the picture on the left. It is well insulated to retain the heat in the rising smoke and gases (heat rises so keeping it hot is good), thus allowing it to be used instead of a stone or brick chimney and outside of a property.

In this situation where there is no chimney, the stove fitter will be looking at the proposed location of the stove and evaluating if a route for the new twin wall flue is possible. He might decide a different stove location is more suitable.

He will look at whether the twin wall flue should leave the room and proceed outside of the building, or whether an internal route through the structure of the building might be the better choice.

He will be thinking about distances to combustible materials and legal regulations on chimney height and performance. He will be bearing in mind the maximum amount of bends he is allowed in the chimney (it’s four by the way – all detailed in the relevant section).

He will take notes on what flue materials will be necessary; what size stove for the room; is an air vent required; is there an extractor fan in this or an adjoining room that might cause problems. He will speak with the householder about stove choice, hearth choice and the process of making good following any holes in walls and ceilings.

With twin wall flue he will also be readying himself to give a price to the customer. Twin wall flue (materials cost, not fitting) is approx. £75 a metre with supports, cowl and other auxillaries swiftly adding up. This is a chimney being built and it helps to bear this in mind when looking at the flue materials costs. A brick or stone chimney would hurt the wallet a lot more.

Twin wall chimney design service