This is a common question we come across in various forms:
- do I need to reline my chimney to install a wood burner ?
- do I need to line my chimney flue?
How Chimneys Work
Basically a chimney is a passage through which combustion gasses vent to the outside air. On a very basic level, chimneys or flues as the is the correct term are positioned above the fireplace so that the by-products of fires, the smoke and dangerous gasses can be transported out of your house safely – without causing any discomfort or danger to you or your family, or indeed the house itself.
It will come as no surprise that a fire when alight produces hot combustion gasses and smoke, as we all know hot air rises, so it is no surprise that the heat from the fire pushes this hot air up the flue and out from the house. All of the time the flue gasses remain not they remain buoyant. If the chimney has cracks in it especially in the exterior section of the chimney stack, cold air will be sucked into the flue. If cold air leaks into the flue, this will cool the hot gasses and have a negative affect on how well your chimney will work. The other danger of cracks in the chimney or between different chimney flues is that poisonous gasses such as Carbon Monoxide (Co) can travel from one chimney flue into another or even directly into another room, either into your property or that of a neighbours. These fumes can prove fatal, with many deaths from Carbon Monoxide poisoning still reported every year.
The “flue” is the passageway through which the smoke and combustion gasses travel from the fire place to the outside air, usually via a chimney, this flue needs to be in good condition and must not leak, if it does the chimney flue will require relining. There are appropriate tests to determine whether or not a chimney is ‘sound’ and does not leak, these are referred to as Smoke Integrity Tests and should only be carried out by ‘Competent engineers’. If it is an older property, this increases the risk. Best practice when installing a wood burner into a Victorian aged property or older would always be to reline the chimney, even if the chimney flue passes the smoke integrity test.
Chimney Liners
Chimneys were historically built from bricks with some form of ‘parged’ liner, usually lime mortar but we have even found parging with horse hair. As houses became older, more and more faults arose so in 1965 when new Building Regulations came into force they insisted that all chimneys built from that day would be lined with a purpose made ‘refractory liner’. These are often clay, or concrete or a specially formed aggregate and these were expected, theoretically last as long as the house. Although, in many cases we have found flues of this age which have failed or become damaged or ones which were just not correctly installed in the first place.
Chimneys built before then weren’t regulated, so if your house is older than 1965, you would benefit from a chimney inspection to look at exactly what state the flue is in – often these houses were built with parging that always gradually deteriorates over time.
But as I said previously, It is worth remembering, that many houses built since 1965 have also witnessed deterioration as a result of the liners not being properly installed, so a safety check is always recommended.
Reasons Why Chimneys Need Lining
There are a number of reasons why an old chimney may need lining.
1. The flue is leaking smoke and fumes into other rooms or parts of the building.
2. Condensates or tar are seeping through the chimney walls causing staining, either inside or outside the building (a common problem with wood burning stoves)
3. The flue is much too large for the type of fire or appliance being used.
4. The flue is too cold, particularly if on an outside wall, and is not drawing properly.
5. If the chimney was built since 1965, but with the liners fitted the wrong way up, tar and condensate leakage may occur.
6. The old flue surface is eroded and rough, causing frictional resistance to the flow of the gasses resulting in soot being held in the flue and increasing the risk of a chimney fire or blockage.
Methods of Lining Your Chimney
There are various ways to reline a chimney, all of which have pros and cons – the best way to determine what is right for your particular situation is to have your chimney inspected by a professional and taking their advice on which method is most appropriate.
Some of the possible you suggestions you could receive are:
- Getting a special coating sprayed on the flue (NB this must be carried out by a by specialist).
- Sections of clay or liner can be installed by cutting into the wall of the flue.
- Fitting a flexible stainless steel (tube) shaped flue liner and now there is a liner which can be inflated into the flue using steam.
- You can have a new ‘cement type’ liner pumped into the original brick flue, this is pumped around a inflated former, which once the material has set hard and dried (cured) the inflated former is then removed.
- But, before any new lining is installed, please remember that you absolutely have to get your chimney cleaned to ensure that the flue is free of all soot and tar deposits.
What To Do Next
We can sweep the chimney and carry out the appropriate smoke tests to determine the condition of the flue, we are GASAFE registered for testing chimneys to be used for gas fires and HETAS registered to test for solid fuel fires. We even have CCTV cameras which we can put into the chimney flue to give us even more information as to the condition of the inside of the chimney.
Give us a ring on 07353 959162 and we’ll be happy have a friendly, no-obligation chat about your individual situation and advise you on what to do next. Alternatively just take 30 seconds to fill in our contact form and we’ll get back to you by return.
We’ll look forward to hearing from you!
For more information about chimney sweeping in London or elsewhere, please check our FAQ page.
