Installing a wood burner into an existing chimney

Installing a wood burning stove into a chimney

Installing a wood burner into an existing chimney properly…

Due to the nature of the housing stock in the UK, installing a wood burner into an existing chimney is a popular choice.

This brief article aims to depict the best way in which to get the most out of your chimney and new wood burner.

Many of the properties in the UK traditionally would have had some form of solid fuel heating.

Often, such heating was by way of an open fire. Further, using coal as a solid fuel was a popular in years gone by.

As a result, many houses lend themselves perfectly when it comes to installing a wood burning or multi fuel stove.

However, it is usually prudent to make alterations to the chimney to ensure proper, safe and compliant installation.

Lets take a look at how….

Our time lapse video offers a reasonable insight….

Altering a chimney breast to accept a wood burning stove?

Over the last decade, carrying out stove installations here at Hot Box, we have never deviated from the following practices.

Importantly, when forming a recess, think big, bigger is better right?

When installing a stove in an existing chimney getting the recess dimensions right will be fundamental.

The sketch below sets out our take on the perfect recess…

installing a wood burner into an existing chimney

The key considerations of any recess are as follows:

  • Making a mess is part of the process, expect to create dust and debris, enough to fill a small skip!
  • Preparation of the working area is key, cover anything and everything that you want to retain, its going to get dusty.
  • Sweep the chimney, vibrations caused when opening a recess can cause a sot fall, always sweep your chimney prior to forming a recess!
  • Dimensions, consider a minimum of 1100mm wide x 900mm high. Bigger is better so far as a recess is concerned.
  • Lintel, over spec this, we favour a 140mm x 100mm Reinforced concrete lintel as a minimum.
  • Inside the recess, a matter of choice, non combustible is necessary, not plasterboard of any description. Check out our range of inglenook chambers… 
  • Hearth, again, a matter of choice, we favour a nice thick piece of slate. Further, make sure you allow plenty of hearth in front of the stove. Legally, 225mm in front of a closed appliance, we prefer 300mm. Further, make sure the original construction hearth is solid, if not, repair as necessary.
  • Making good the face, a smooth plaster finish, normal plaster will suffice for a recess, feather it in or re plaster the whole chimney breast. Some work with a trowel and some lightweight filler when decorating will create a good finish. If perfection is needed, go for a full re plaster of the entire chimney breast.
  • Skirting boards, nothing combustible should be placed on the hearth! Truncate the skirting boards at the edge of the hearth, if an up stand is needed, use the hearth material in place of timber.


What will I need to create a fireplace recess for a wood burning stove?

Here at Hot Box, we would recommend the following equipment to for a suitable recess for a wood burner. Installing a wood burner into an existing chimney.

Forming the recess….

installing a wood burner into an existing chimney

Making good the recess…

a completed installation into an existing chimney

Clearly, much of this is down to personal choice but, in short, you will need…

  • A reinforced concrete lintel. 
  • Plaster, bonding coat and multi finish is the usual.
  • Sand and cement, used for making good around the lintel and bedding the hearth.
  • Material for the recess, either a chamber or material to render it. NEVER use plasterboard of any type!
  • A hearth, non combustible and suitably durable, stone, slate, granite, marble, concrete. The choice is ours.
  • Other useful items include PVA glue, a selection of hand tools and plastering sundries such as beads etc.
Now that you have formed the recess, lets look at installing the stove….

Installing a wood burner into an existing chimney can now commence.

A new recess has been formed and the messy part is now out of the way.

Commonly, the sketch to the left presents what you need we installing a wood burner into an existing chimney. The safest method, as recommended by HETAS, is to use a flexible flue liner.

Clearly, to line an existing chimney you will first need to consider access. At Hot Box Stoves, we often favour the use of a Cherry Picker, in place of ladders. However, the most important consideration should be safety.

More over, you will need the following components to install your wood burning stove…

From the top of the stove to the top of the chimney…

  • Stove pipe, a minimum of 600mm of vitreous enamel pipe should be considered off the top of your appliance. Always consider the size of the outlet on your stove, 5″ or 6″ are the most popular. Further, consideration needs to be given as to whether or not a soot door is required for sweeping the flue. A soot door will be needed if our chosen stove cannot be ‘swept through’.
  • Flexi to stove connector, a critical component in any stove installation. This piece connects the liner to the stove pipe and takes the brunt of the heat from the smoke and flue gasses. Hot Box favour Schiedel. 
  • Flexible flue liner, don’t be tempted to buy cheap, you will buy twice. There are two grades available which relate to the quality of the steel used. 316 grade and 904 grade. Again, as with all components, we favour Scheidel Tecnoflex. 
  • Terminals, for ease of installation and future removal, a pot hanging terminal is an obvious choice. Again, this should be sized to suit the liner and other installation components.
What else will be needed to when installing a wood burner into an existing chimney…

Moreover, when embarking upon lining a chimney you will need to consider the following additional items.

The Hot Box team use metal register plates, minimum of 2 mm thick. Further, our teams of installers carry a comprehensive range of fixings, sealants and paints, suitable for high temperature installations.

Additionally, The Hot Box vans are always stocked with a comprehensive range of power tools to get the job done.

Hot Box Stoves Limited powered by Hilti….

In conclusion, tackling the task of installing a wood burner into an existing chimney is of course possible by yourself. However, The Hot Box team can ensure it is safe, compliant and 100% fit for purpose.

Our advice, Book a Survey, our engineers are here to help.

Common mistakes…

Numerous errors usually made when forming a recess, avoid these to save future issues or the need for alterations.

  • The use of pink ‘fireproof’ boards inside a recess. This is not a suitable product for use inside a recess housing a woodburner.
  • Installation of the lintel so as to cause a restriction for the flue pipe. Always remember, the largest face of the intel should the vertical face.
  • Recess made too small, always consider the simple rule, 600mm of stove pipe is required off the top of an appliance before it connects to a flexible liner.
  • Beams placed too close to stoves. This is critical, the rules are, anything combustible should be well away from the stove (see manufacturers guidelines) and at least three times the diameter away from the stove pipe.
  • Hearths made too small. Building regs state 225mm in front of a closed appliance, Hot Box prefer 300mm, better to be over specified than under!

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