Using an open fire, wood burning or multifuel stove
Using an open fire or stove safely in a thatched home is fairly straightforward, as long as you follow some simple rules.
- Try to make sure all chimney tops are at least 1.8m above the thatch. This will allow sparks to escape and die out before they settle. The deeper the thatch around the chimney, the greater the risk of fire. You may need planning or conservation approval if you need to raise the stack height. If you can’t raise it, remove any capping devices on your chimney, as they tend to deflect sparks downwards.
- Get a professional chimney sweep to clean all your chimneys – once before the first fire of the season, and again if the chimney is used frequently during the winter. The sweep must be a member of one of the following organisations:
The National Association of Chimne
y Sweeps (NACS)
The Guild of Master Chimney Sweeps
- Have your chimney endoscopically inspected to ensure that the brick or stonework and any flue lining is in good condition, especially where it passes through the thatch. Any gaps or cracks should be repaired immediately. There are a number of companies that offer inspections at a reasonable price and we have named one in the Useful Contacts.
- If you’re using a wood burning or multifuel stove, you can check the possible flue temperature at the point where the gases leave your stove by fitting a flue thermometer. This will help you to check that the flue isn’t getting too hot at the point where it passes through the thatch. Consider a chimney heat detection system.
- If you have a wood burning stove, use hard woods that have been seasoned for at least two years and have 20% moisture content or less.
- Make sure all open fires and stoves are completely out before you go to bed or leave your home for any length of time.
- Burn paper in a stove with the doors open.
- Burn wet or unseasoned wood – this will leave flammable tar deposits in the flue and may
damage your flue liner.
- Fit spark arrestors to chimneys. A blocked spark arrestor can slow down flue gases and
allow a build up of heat. If you do have them, clean them thoroughly every year towards the end of summer, before you start to use the chimney. Take care not to damage your thatch when you’re accessing arrestors.
How to use your stove safely
- Start your fire with commercial firelighters and very dry, small logs. If possible, avoid kindling completely – especially smaller sticks, twigs, shavings, cardboard and paper, which can produce a surge of sparks.
- You should only burn hardwood that has been seasoned for two years and is less than 20% moisture by volume. Don’t burn coniferous wood or builders’ wood waste, or use the stove as an incinerator for general rubbish.
- Don’t just ‘throw a log on the fire.’ Add fuel carefully to minimise sparks and flying embers.
Heat transfer fires and flue linings
Not every thatch fire starts with a stray spark. Wood burning and multifuel stoves generate high flue gas temperatures, often between 300oC and 600oC.
Source: The National Society of Master Thatchers Limited
If high temperatures travel through the brickwork of the chimney to the thatch – a process called heat transfer – there is a risk of thatch fire. The thatch can itself make the problem worse because it insulates your chimney at the point where it passes through the roof.
Heat transfer isn’t just a problem for stove owners. Homes with normal open fires can also suffer from the effects of heat transfer. A Chimney Heat Detection System can help you check the temperature in your flue and reduce the risk. You can buy these systems from the providers listed in the Useful Contacts.
The heat transfer process can cause thatch to smoulder and ignite when it gets hotter than 200oC. The danger zone for heat transfer and thatch ignition is shown in red in the diagram. You probably face a greater risk if your thatched home is old and/or listed.
Old and inappropriate flues.
- A multi-layer wheat straw thatch that is more than a metre deep.
- Regular use of a multifuel or wood burning stove with an inappropriate or badly-fitted
- Overloading fuel in the stove and over-venting. This gives the fire too much oxygen, which
makes it burn faster and hotter.
- A central chimney that is surrounded by thatch, or a thatched home that is part of a terrace.
- A blocked or tarry spark arrestor.
- A poorly-installed stove or flue liner. When you fit a stove or flue liner, make sure you use the
services of a professional who has experience of thatched properties.
Old and inappropriate flue liners are a common cause of thatch fires. We recommend that you get a professional installer to check your flue liner regularly and make sure it is adequate for your stove or fire. If you’re thinking about re-lining your chimney, we’d recommend one of the following:
A liner of one of these types will greatly reduce the transfer of heat through your home’s brickwork, which in turn will reduce the risk of thatch fire.
Although there are several different ways of lining a flue, only linings that are rigid, insulated, and capable of being correctly supported and centralised are suitable for thatch. Flexible stainless steel liners used to be popular, but we no longer recommend them: it’s difficult to control their angle in the chimney, which can result in direct contact with the brickwork and subsequent
Lining your chimney
• A lining made of pumice, clay, ceramic or concrete.
• A twin walled rigid system – a steel inner and an outer lining filled with rockwool. • A steel outer and ceramic inner lining filled with rockwool.
Where there’s no alternative to a flexible liner, it must be fully bracketed, centralised and supported along its length. You should also use a proprietary insulation material where possible to give further insulation. A chimney specialist with experience of thatched homes will be able to give you advice about your particular setup.
A badly fitted flue liner can cause a thatch or chimney fire, so when you’re having one fitted be sure to use an installer accredited by a professional body such as HETAS or NACE.
Source: HETAS PDF
Chimney Heat Detection Systems (
There are several products on the market that detect when your chimney flue has become dangerously hot. When a pre-set temperature is reached at the level where the chimney meets the thatch, an alarm sounds. When you hear the alarm you can take immediate action to damp down your stove or fire.
We recognise two systems: the Thatch Alert System (as seen in the Fire Protection Systems illustration) and the Phoenix System produced by Thatch Fire prevention Ltd.
Some companies also offer monitoring services, in which the heat detector is linked to an approved alarm centre that calls you, or the Fire Service in your absence.
Before you install any system please talk to your insurance advisor. It’s also important to remember that the most effective safety system in your chimney is an adequate, properly installed liner. If you have a faulty liner, a detection system will only give you a false sense of security. Furthermore, detection systems only monitor chimney heat: they won’t prevent or warn of fires started by sparks or flying embers.