NACS registered · Fully insured · Free smoke draw test and certificate included
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NACS registered · Fully insured · Free smoke draw test and certificate included
★★★★★ Rated 5 stars from Google reviews
NACS registered · Fully insured
Practical guidance from a NACS registered sweep — how often to sweep, which fuels to burn, what ventilation you need, and how to avoid a chimney fire. Written for homeowners, not for other sweeps.
It is commonly believed that only gas appliances produce carbon monoxide. In fact all appliances that burn fuel produce it, and your solid fuel stove or open fire produces hundreds of times more than a gas or oil appliance. This, together with the risk of a chimney fire, is why it matters that your chimney is swept by someone trained and competent.
UK fire statistics show that on average more than 31,000 homes have a chimney fire each year. Around 9,500 of those cause damage to the property. A significant number are down to chimneys simply not being swept often enough. Other contributing factors are:
A NACS chimney sweep will be able to give you good basic guidance on using your appliance and your fuel. That advice may well save you the cost of the visit in fuel savings every year.
It depends far more on what you burn than on the appliance itself.
| Fuel | How often |
|---|---|
| Smokeless coals | At least once a year — often wrongly believed not to need cleaning |
| Wood — open fire | Once a season when in use |
| Wood — stove | Twice a season when in use |
| Bituminous coal | Twice a year |
| Oil | Once a year |
| Gas | Once a year |
If your chimney is clean it will not catch fire — there is nothing in it to burn. See our chimney sweep services for what a sweep involves.
Most insurance companies will no longer pay out for chimney fire damage unless the flue has been swept and maintained by a professional chimney sweep who can issue a valid certificate of sweeping that insurers recognise. NACS sweeps are required to issue these certificates for every chimney cleaned.
There is a second cost too. If the fire brigade is called out to a chimney fire and it is shown that the chimney has not been maintained, the local council can bill you for the call-out.
Check your policy. Make sure you know the sweeping frequency your insurer requires. Your NACS sweep may recommend sweeping more often than your insurer asks for, depending on your setup and what they find in your chimney.
It is very important to burn the correct fuel on your solid fuel appliance, both to keep the appliance and flue in good condition and to get efficient use from it.
Make sure the liner fitted is suitable for the fuel you want to burn, or that your fuel is suitable for the existing liner. Using the wrong fuel on a liner shortens its life considerably through increased corrosion, and creates a dangerous situation. Liner life can drop to as little as three years if the wrong fuel is used.
The flue will also soot up far faster, because the appliance is running less efficiently — which in turn increases how often it needs sweeping to stay safe.
Burning coal or smokeless fuel in a wood burner produces very little heat but a great deal of soot, because the appliance was never designed for it. Burning wood on an open fire gives little heat for a lot of fuel, and heavy fuel consumption means more soot and tar.
Only suitable seasoned timber should be used in solid fuel stoves. Never burn man-made wood such as MDF, plyboard or chipboard. Doing so gives low heat output and builds tar in the flue. Tar is highly flammable and carries a very high risk of chimney fire. Removing it is specialist work and expensive, because it cannot be removed by normal sweeping methods — where the build-up is severe it is often easier to remove the liner and fit a new one.
Be wary of the word “seasoned”. Many retailers sell wood described that way. The only thing that actually matters is moisture content, and it should be under 20%.
Wood storage matters more than people expect. Logs need a dry store that lets air move around them — stack them, do not pile them. Good ventilation matters more than keeping the rain off; correctly stacked logs will keep losing internal moisture even if they get rained on occasionally. That said, the best store has a roof.
If wood is not kept aired it starts to rot, which means it will not burn fully and gives out less heat.
There is more on testing and storing logs in our guide to whether your logs are dry enough to burn.
It is very important to let your solid fuel appliance breathe properly. Without enough air the flue cannot take fumes away effectively, which leads to smoking back or slow gas speed — and the flue sooting up more quickly. Insufficient air flow also causes incomplete combustion, low heat output and increased pollution.
For an open fire, with or without a boiler, you need an air opening or openings with a total free area of at least 50% of the throat opening area. For a typical open fire that is usually 16,500mm². This is ventilation to the room from outside the building.
The requirement depends on the size of the stove and when the house was built.
| Property and appliance | Ventilation needed |
|---|---|
| Built before 2008, stove up to 5kW | No vent required |
| Built before 2008, stove over 5kW | 550mm² per kW above 5kW — an 8kW stove needs 1,650mm² |
| Built after 2008, any size | 550mm² per kW — an 8kW stove needs 4,400mm² |
Note that it is sometimes necessary to fit a vent in an older property with a 5kW stove if there is not sufficient air flow. Your NACS sweep will be able to advise on your ventilation requirements.
Chimney fires can burn explosively — noisy and dramatic enough that neighbours or passers-by notice. Flames or dense smoke may shoot from the top of the chimney, and homeowners often describe a low rumbling sound like a freight train or a low-flying aeroplane. These fires will most likely cause damage.
That damage may not be obvious afterwards and everything may seem fine — do not use the appliance or chimney again until a full survey has been carried out and a report produced. This applies even more to steel chimney systems.
Those, however, are only the chimney fires you know about. Slow-burning chimney fires do not get enough air or fuel to be as dramatic, but the temperatures they reach are very high, and they can damage the chimney structure and nearby combustible parts of the house.
There are two main reasons a chimney stack gets damaged: a chimney fire, or weathering with age.
A chimney sits in the most exposed part of the house. It takes sun, wind, rain and frost for years — and then we light fires under it and fill it with corrosive soot that eats away from the inside. It is no wonder it needs maintenance from time to time.
The chimney’s other problem is that it is on top of the house, where the owner never looks at it. It usually only gets inspected once something has gone wrong, by which point the damage is further along than it needed to be. Your local NACS sweep will always check the stack, usually with binoculars, before sweeping the flue — to confirm it is sound and that sweeping will not cause further damage.
Damage to the stack and flue affects how well your chimney performs and reduces its ability to clear harmful gases. Flue damage can also let those gases leak into bedrooms and loft spaces, which in extreme cases can result in injury or death. This is why we recommend a full survey of the installation and flue before it is used again after a known chimney fire.
Fire and weather damage to a stack brings one further risk: masonry falling from height, which can cause serious damage to property and injury to residents or passers-by. This will not arise if your chimney is swept annually by a NACS sweep, because the stack gets inspected and repairs get recommended early. It is worth staying on top of those repairs, as insurers will not pay out for large-scale wear and tear.
Practical guides written for homeowners.
We are NACS registered and fully insured, sweeping across Greater Manchester. Every sweep includes a free smoke draw test and a NACS Certificate of Chimney Sweeping. From £75.
