How to Clear a Blocked Chimney

This chimney cap will prevent a blocked chimney from occurring.

This chimney cap will prevent a blocked chimney from occurring.

Blockages in chimneys occur for a variety of reasons. Take, for example, a normal fireplace flue. If this flue was not capped by a chimney cap, it was be extremely easy for birds, squirrels, or other critters to climb into the chimney bringing large amounts of nesting materials with them. This nesting material can completely block your flue, preventing the chimney from drafting properly. This material is extremely flammable; flues are not meant to contain fires only the products of combustion. If this nesting material were to catch on fire and the flue were to contain this fire, flue tiles could crack and the entire chimney could catch on fire.

Always, always, always unblock from the bottom. Never unblock a chimney from the top. In cases of nesting material there are corkscrew attachments that can be put onto cleaning rods to actually hook into the nesting material and lift it out.

If you are dealing with a chimney that is venting two different flues, say the furnace and the hot water heater, the white wall that is between the two flues may buckle and block the flue system. This can cause these appliances to vent improperly. You may have a carbon monoxide detector go off if this is the case because often times the gases that are the products of combustion from gas appliances cannot escape the chimney. In this case you would unclog the flue from the bottom. You may need to widen the bottom opening where the appliance connects in order to successful unblock the flue system in this case. Signs that a white wall has collapsed would be the appliance immediately shutting off or the carbon monoxide detectors going off.

The flue is not properly unblocked until one of two things occurrs. First, if the flue has no bends or offset flue tiles, the flue is properly unblocked when you can tilt a mirror up the flue and see daylight (when the cap is removed, of course). If there is a bend or offset flue tiles, the flue is properly unclogged when you can run a sweeping rod the entire way up the flue system to the very top.

Clearing out a blocked chimney can be very expensive, especially if the sweep charges per hour and takes a long time to remove compact debris. The best way to avoid a blocked chimney is to install a chimney cap. This cap will prevent animals of all shapes and sizes from bringing any nesting material into your flue. This will prevent costly chimney repairs if a fire catches up in the flue system.


7 comments on “How to Clear a Blocked Chimney

  1. Freda Forde on said:

    My chimney is blocked with what seems like a lump of wet soot the chimney cleaner could not get through it is there something I can burn that will soften this lump The chimney is still pulling well and not blocked

  2. The wet soot needs to be removed either up or down the flue, or by cutting into the side of the chimney
    It’s possible that you have a broken flue tile that is causing a problem and blocking the chimney flue gases. I would think that this problem will only get worse if it is not addressed
    Burn Safe and warm.
    - Clay

  3. Hi just wondering what to do…. i had a multi-fuel burner installed & everything was fine untill my neighbour decided to have one fitted we share the same chimney. Now i’ve had nothing but trouble…. He’s had a liner put into his & blocked up mine in the proceed… Bricks fell down my side whilst they was fitting the liner but they didn’t say anything……. i just noticed it wasn’t drawing properly, i ended up knocking on his door & telling him what had happened so he sent his builder round, of which he was very apologetic & said he would send his chimney sweeper man round to sweep it.. The man’s been around & swept it & you could hear the bricks fall… Everything was fine for a few weeks then all the family started having mirgranes/head aches feeling sleepy so i purchased a carbon monoxide detector…. i lit the fire that night & the alarm went off about 8 times in the end my friend called 999 an ambulance…Fire brigade & gas man ended up at my house with all the family been tested for cmp…. luckly we was fine but the fire is not!!!! I’ve spoken to my neighbour & told him what’s happened, he said he’ll speak to his builder but still nothing, i’ve been without the fire 6 weeks now Help

  4. sorry i forgot to mention that i phoned the chimney man back myself & he tried to put his rods up but could only go up to around 5ft… he thinks the middlewall collapsed… He said it’s the next door neighbours fault & he hasn’t even put a chimney cover on yet so the chimney is all open to the weather & he hasn’t given him a certificate because the chimney man didn’t do all the work!!!!

  5. Hi, I live in a semi detached two store house built in the 1920s. We have an open fire that was swept when we moved in two years ago. We use it only in winter maybe twice a week and without issues. I’ve just had a chimney sweep out to do it again because it was due, and he says he’s found a blockage about 7 meters up. He said he couldn’t sweep it and wanted to come back to do a ‘CCTV’ examination (for 50 quid) then come back again based on that outcome to sweep it. I feel like I’m being taken for a ride here – he charged me £30 for that visit even though nothing was done, wants to charge me more for CCTV and more then to sweep it. Shouldn’t he have tried to remove the blockage? What would you suggest I do? Thanks for your time

  6. hiya

    I wonder if you can help. Our fireplaces are sealed off but we have a lot of damp coming through the chimney breast upstairs. The exterior of the chimney is dry so we think this must be condensation caused by lack of ventilation caused by a blockage. Looking and poking into one of the flues from the roof there is about 3 foot of heavily compacted nest material which is proving really hard to shift. Any ideas? Thanks

  7. You might call three or four local chimney sweep contractors in your area.
    I sure you will feel comfortable working with one of them!
    -they will offer 4 different opinions or solutions ;(
    Nesting blockage could be cause condensation issues
    I think you may have figured out the cause of the problem?
    now for the solution

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