My fire smokes back. Should I fit a cowl to the chimney pot?

That's a good question and there is no straight answer. There could be other things to think about first.

1/ You could have a ventilation problem. Try opening a window or door slightly and see if the smoking stops. You may have to try various doors/windows on different sides of the house. If this improves matters you could well need better ventilation. Smoking back can coincide with fitting double glazing or draught proofing because you have cut off the draughts that were feeding the fire.

2/ Are there trees (e.g. Lalandii) that have grown up tall near the house over the years? With the wind in a certain direction, nearby trees can cause unseen disturbance to the air flow over the house. Nearby buildings can have the same effect if the wind is in a certain direction. Your property may not be built correctly. Roof lines and chimney height have a considerable effect on the way a chimney “draws”.

3/ Is the wind blowing or gusting from an unusual direction? This can cause smoke to blow back down the chimney. This is related to reason 2 above and you may not be able to do anything about it. You may simply have to wait until the wind changes back to a favourable direction.

4/ Have you made changes to the fireplace or chimney? One of my customers had a chimney pot fitted to a stack that didn't have one before. The fireplace started to smoke back and they wondered why. The new pot was far too small and was bedded onto pieces of slate that created an even smaller square hole under the pot! Trouble is, the householder was reluctant to contact the builder again to put it right. The same (or converse) can be true if you have “opened up” the fireplace. There is a mathematical relationship between the size of the fireplace and chimney pot. If the fireplace is too large or the chimney pot too small the smoke will not get away.

5/ Does your chimney need sweeping? That may seem an obvious thing to ask, but time flies as they say, and it may be longer than you thought since you had it swept. Coal is not as good quality as it was. It can come from as far away as Russia, Columbia or even Australia. So chimneys do soot up quicker than they used to. You may have a birds nest or other obstruction that needs clearing.

6/ Have you opened up another fireplace in the house? The chimneys will be competing for air and one may win.Air may then come down one chimney in order to feed the air going up the other.

After thinking about the above, you may try a cowl. Make sure its not a vent designed for redundant chimneys. There are dozens of cowl types and makes. Some specially designed chimney pots act as cowls. You can even get special fans that “suck” the smoke up. All I can say is, the more complicated types have more to go wrong. They are usually more difficult to fit and sweep too. But it may be the only way to stop smoking back.


How do I stop birds coming down the chimney or nesting?

There are some do’s and don'ts.

Do fit a suitable bird guard to gas/oil appliances. Consult a qualified heating engineer for advice on these.

Do fit a proper bird guard to the chimney pot, if at all possible.

Do act quickly. Jackdaws can build a nest in a few days.

Do concidder. Nesting birds may be protected by law. Consult the R.S.P.C.A. before disturbing.

There are a variety of makes and types available. Try your local builders yard. The one I prefer is made by Jack Door at Shepton Mallet. Tel: 01749 344015. www.jackdoor.co.uk . It secures simply by a band around the pot, which is better than some that have hooks inside the chimney that can work loose in time or others that simply spring out inside the pot.Mendip Fireplaces will post one to you. If your chimney doesn't have a pot and is just a large brick opening, get a cage made up to the size of the chimney top. Weld mesh is a good material. Similarly, if you have a “dove cot” top, (i.e. a slab on four brick corners) fit weld mesh around the open sides. Nothing less that half inch squares/holes. Smaller mesh gets clogged with soot.

Don't push netting down the chimney. It becomes choked with soot and when the chimney sweep comes along, his brush either pushes it out, or he can’t get the brush through. Sweeps brushes can get tangled on things inside the chimney too.

Don’t use the appliance/fire until all the nest is cleared and removed. A nest can cause poisonous fumes to come into the house. This is especially dangerous with gas, as there is little or no smell with the fumes. Also nests can catch fire and warm the house rather better than you intended.

Don’t forget - things that are exposed to wind, rain and fumes will deteriorate. Something metal fixed to your chimney pot will eventually come off. It could end up gracing the bonnet of your car (or worse, the mother-in-law‘s bonnet).


Should I have my chimney lined if I fit a wood stove?

I’m sorry but the short answer is yes (unless it is already lined). The reason is that chimneys with wood stoves don't work the same way as those with an open fire. Let me briefly explain:-

With an open fire, a lot of heat goes up the chimney. As the inside of the chimney gets hot with the rising  smoke, it “cooks” much of the tarry substances that collect and it forms into a clinkery soot that is comparatively easy to sweep. Also much of the smoke simply passes through the chimney and becomes someone's acid rain.

However with wood stove, a lot of the heat is extracted from the flames & fumes by the stove (after all that’s what you want) and the smoke that goes up the chimney is cooler and moves much slower. As the smoke rises further it cools even more and starts to condense, forming a thick, tarry substance. This can happen even with so called “smoke eater” stoves.

When the sweep comes along, he will probably find it hard to get into the chimney because you have put a wood stove in the way of the fireplace and when he finally does get his brush up the chimney, very little soot will come down. The chimney will be coated with a shiny black layer like a tarmac road.

1/ The tar will eventually catch fire, and with all that tarry fuel up the chimney it could be quite spectacular.

2/ The tar may penetrate the wall up in a bedroom or drip down inside the chimney and create a black puddle at the back of the stove.

3/ The tar will probably smell (this seems to be especially so on humid summer days). Some people like the smell, but after a while it can become so pungent that you get sick of it.

So don't take any notice of people who say you don’t need a lining. Additionally the lining should be of the correct grade and be insulated. Your local builder is unlikely to know all the intricacies. You must follow building regulations and may need planning permission for some of the work too. Best to consult a chimney specialist. 

See the links page for more information.