This chimney cap will prevent a blocked chimney from occurring.
This chimney cap will prevent a blocked chimney from occurring.

Blocked Chimney?

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 don’t contain fires, only the products of combustion. If this nesting material were to catch on fire, the entire chimney could catch on fire.

Unblock from the bottom

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. They actually hook into the nesting material and lift it out.

Two different flues?

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, the gases that are the products of combustion 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.

Two things to do…

The flue is not properly unblocked until one of two things occurs. 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.

Get a chimney cap!

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.

Clay Lamb

Clay Lamb is a Cincinnati Chimney Sweep contractor and the executive producer of the YouTube channel, podcast, and blog Ask the Chimney Sweep. He is also an award-winning educator and public speaker in the chimney and fireplace industry.….Educational Videos….American Chimney Cincinnati, OH

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.
Clay Lamb

Latest posts by Clay Lamb (see all)

26 thoughts on “How to Clear a Blocked Chimney

  1. 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

  8. As a temporary message I put thin plastic wrapping paper in my chimney opening to prevent soot failing. The draft from the chimney has taken the wrapping up the chimney . how can I retrieve this.

  9. My mother lives in a house that was built in the early 1900’s. The chimney has had issues now for about 6 years. We installed a triple wall pipe down through the chimney. This is the 3rd year that it has been in and when they go to clean out this year it is so stopped up they cannot get anything through the pipe. Do you have a suggestion as to what can be done. We do not have a chimney sweep that works in this area.

  10. I would venture to guess that the creosote has been collecting on top on the spark arrestor, and is now causing sluggish draft. This has now blocked the flue system, often this is because the damper was chocked down to far. Are you searching the site for a Chimney Sweep?
    Search for the online or call the office and request a sweep that will service your chimney.
    This a very serious problem that needs to be resolved before using the fireplace or wood-stove.

  11. Hi I had my chimney cleaned about 3times this year the last time the chimney cleaner couldn’t get his brush up the full way every time I light fire it is smoking what do u think my problem is

  12. I would guess that it most probably is one of more of these issues.
    1) A collapsed flue tile that is now blocking your chimney venting system.
    2) Puffed or swollen creosote from experiencing a chimney fire, < --(and possibly, is cover under your home owners insurance policy). 3) An originally construction default, where the flue tiles was laid in at a 90 degree angle, and is now stalling the gases down from exiting out of the top of the chimney. The max angle most often called for is a 30 degree bend. This is so the flue gases will draft out properly. Other culprits might be burning wet wood, an keeping the damper closed fairly tight to often. I have not seen a clogged chimney flue that we could not open up, it may now need to be opened from the outside brick into the flue system. We always start unclogging a chimney, going from the bottom up. We do this so that we don’t pack any debris further down in the flue system. To find a reputable Chimney Sweep in your area, use this link to the National Chimney Sweep Guild locator: Also be sure to go online and read their customer reviews from Google, BBB and AngiesList. If I had three different service men to my home, I would ask them “what do you feel is the problem” with my chimney system?
    keep pushing for the answer I think your getting closer to a solution!
    Burning Safe & Warm!
    Clay Lamb author of: – Youtube Educational Videos – Professional grade Chimney products – Contractor Coaching Podcast – GM @ American Chimney Sweep Cincinnati, OH

    * Signs of a Chimney Fire

    *Sudden Occurrence < --Insurance claimes

  13. We heat with wood our chimney is brick there seems to be a block we think melted plastic how do we fix this without taking down the whole chimney ? We are very handy and our funds are limited.

  14. Ok I’ll bite here what could the plastic be, construction materials or something dropped down the chimney while attempting to unblock the chimney. What makes you think it is plastic? Most Chimney Contractors will begin unclogging a chimney flue by working from the bottom of the chimney and plunging upwards with an assortment of rods and different types of hook and piecing arrow type heads. To find a reputable Chimney Sweep in your area, use this link to the National Chimney Sweep Guild locator: and be sure to go online and read all of their customer reviews from Google, BBB and AngiesList
    Clay Lamb author of: – Youtube Educational Videos – Professional grade Chimney products – Contractor Coaching Podcast – GM @ American Chimney Sweep Cincinnati, OH

  15. We have a wooden holiday cabin. The chimney is not drafting well at all and is smoking Six months ago we did a d.i.y. job of sweeping the chimney. Brushes were pushed down from the top. I have just read that this should never be done. Coal and wood is burned in this stove and there is a heavy metal plate on the roof of the stove which is almost impossible to remove because of the weight. Any advice please?.

  16. You have a lot of variables in your post.
    This is way to serious of a matter to try and resolve over the Internet.
    Let me start off with this, I would think it is time, for you to pay a professional
    chimney contractor to complete a chimney cleaning and inspection.
    As you said this is a wooden cabin and that is a big concern!
    What is causing this smoking problem may be another serious issue that you may need to deal with?
    Is it a freestanding stove connected in the ceiling or wood stove insert?
    If it is an insert is it properly line according to the manufacture listing
    Is this a UL listed stove?
    Does the Mfg allow for the use of both wood and coal, as coal burns much hotter?

    *To find a reputable Chimney Sweep in your area, use this link to the
    National Chimney Sweep Guild locator:
    Be sure to go online and read all of their customer reviews from Google, BBB and AngiesList.
    I want you and your family, to have wonderful memories of Holidays at your cabin, not sad ones!
    Clay Lamb author of: – Youtube Educational Videos – Professional grade Chimney products – Contractor Coaching Podcast – GM @ American Chimney Sweep Cincinnati, OH

  17. My stove pipe keeps clogging up. I am using well seasoned wood. It’s a free standing wood stove with 6″ pipe. I had a princess, blaze king stove which was great but had to clean my pipe 3 – 4 times every winter season because it clogged up. I thought my problem was the wood stove, that the catalytic converter or something was doing it. This year I replaced my wood stove with a cheaper, England wood stove, Englander, just like the one at my son’s house that has never been a problem. We use the same wood so again, the wood is well seasoned and not the problem. The only difference in my stove is that my pipe runs aprox 20 ft up and his is aprox 15 ft. I live in S Dakota and have used wood stoves for many years and never had this problem. I had my stove pipe cleaned before this season and I’ve had to clean out the pipe once already and now, again aprox 2 weeks after cleaning it out it’s clogging up again and needs to be cleaned. Hard to light a fire, smokes you out to open the wood stove door, so definitely clogged up again. Do I need a damper in the stove pipe because it runs aprox 20 ft? I can’t figure out for the life of me why it keeps doing this. Any suggestions would be greatly appreciated.

  18. Chris, when you think of it, most fireplace or stove systems are not complicated, they’re very simple or may I say somewhat primitive in design. It is been my experience that more often than not, these are operator issues. It may be something that you’re “knowingly doing or not”. Please don’t take my statement personal or offensively, as I’m speaking to a much larger audience than just you and me, and those other readers of my blog may be searching for the same answer to this problem in the years to come. Join me as I try to dissect this creosote problem, one idea at a time.

    While you’re on this investigation journey, I would suggest documenting each day; the outside temperature, time that your loading the firebox, and the burn time per load. Additionally, I would note any outside chimney cap or smoke observations.

    ( Firewood )
    As you stated, the wood source you’re burning is the same wood as your son, and that he is not experiencing the same problem as you are. So I would have to dismiss the wood source as the problem. For me, I have used many different wood stoves over the years, at night before going to bed, I filled my wood stove firebox approximately 75 to 80% with wood.
    I would get that fire really going, then turn the damper back (appx 80%) before heading off to bed. When I get up in the morning, I will get a good hot fire going for about 20 minutes with the woodstove door open. Then I will reload the firewood and turn the damper back.
    I do this practice, in hopes of heating up the entire chimney flue pipe, thus flushing those over-night cooler gasses up out of the chimney system. I have always caution myself on dampening or choking down my stove, as I want a hotter chimney stack temperature to provide a really good chimney draft.

    ( Draft and Stack Effect Temperatures )
    To set the stage here, I find it rather unique that this problem was not occurring at your son’s home. Also, you’re using the same stove, and that your chimney stack is actually taller than his by 5’. I have found that this additional 5 foot of height would have consistently introduced a much better draft up the chimney.
    For our other reader’s benefit, I noticed that there is no mentioning of back puffing into the living space. Back-puffing might be associated with negative air pressure within the home. Negative air pressure issues could be brought about by both attic and bathroom fans, and even fans on our kitchen stoves. Other sluggish draft culprits to be noted could be associated, are those taller or cathedral types of ceilings. It is also important to note that those larger staircases that are adjacent to or in close in proximity to the wood stove could be problematic in some situations. The reason I mention this is because sluggish draft or lingering smoke really doesn’t care if it goes up the chimney or up or out another “path of lesser” resistance.

    ( Chimney Cap and Spark Screening )
    For me, I would “temporarily remove” the chimney cap, especially if it has any type of screening or spark arrestor. Your chimney cap and / or screening could be clogging with creosote over those very cold Dakota cold nights. Also, consider that this is the longest period for a colder sluggish draft and is actually the time that your stove is not being attended to at all. This creosote could possibly be blocking the exiting of the gasses at night, then this creosote may be liquefying and dripping back down the chimney flue system, coating the entire interior of the flue. This possibly could be creating a very sluggish draft of smoke trying to exit.

    ( Creosote Modifiers )
    I would recommend using A liquid are granular creosote modifier, such ACS or Cre-away. Be sure to follow the directions by the manufacturer in the usage of either product. To be totally transparent here,and I want to state that I carry both of these products on my online website

    ( Catalytic Converter )
    If there is any type of catalytic converter in your system I would temporarily remove it or at least keep it in the bypass position. In the past, many catalytic converters were damaged, fouled out, or blocked with ash blockage. Also note that there is an actual “light off temperature that MUST be achived, before actually engaging many cats, as described in the owner manuals. Most manufacturers have a customer service phone number for problems like these, and I would not hesitate to call them!

    (Chimney flue Size )
    The opening on the stove should be the same square inches throughout the entire run at the chimney venting system (an example of this would be a 6-inch outlet opening found on top of the stove and a 6-inch interior dimensions on the chimney pipe all of the way to the very top.
    Any horizontal connector within the venting system needs to maintain a 1/4” rise per foot of horizontal run (ie; connector pipe) .

    Chris, I really do hope that bouncing these ideas around will be of some help to you. As a side bar note; the manufacturer of your wood stove is your real voice of authority and they have engineering departments and customer service phone numbers for these types of issue, and I would not hesitate to contact them!

    Burn Safe and warm
    Clay Lamb author of: – Youtube Educational Videos – Professional grade Chimney products – Contractor Coaching Podcast – GM @ American Chimney Sweep Cincinnati, OH

  19. Thank you so much for your informative reply Clay. I have used the granular creosote modifier to no avail. Opening on stove is 6″ and all pipe above is 6″. My ceilings are 9 ft throughout the house but not cathedral.
    It does “back puff” at times, ignites and go back out ignites again sometimes several times before it stays lit (I can see if its flaming/fire thru the glass), I’ve always associated that with the pipe getting clogged because I haven’t know any better until now thanks to your info.. After this last cleaning of pipe I’ve burned just hot fires in it with damper open 80 to 100% and at night leaving it open aprox 80%. My son was telling me to only burn hot fires with damper opened up which I did this last time to no avail.. I don’t know if I could burn a hot fire for 20 minutes in the morning with the door open too much smoke would come in house even if the pipe is just cleaned. So, now saying that and with your info I’m obviously thinking it is most probably a draft issue.
    I live alone and rarely use a bathroom fan and can’t remember last time I used the kitchen stove fan. However, my house was built in 2014 and been having this problem from the get go. My house is a steel building with great insulation and windows, very tight so perhaps the negative air pressure is the issue somehow.
    My cap doesn’t have wire mesh and the smoke pours out but maybe it is building up at night as you say but again, my son’s cabin is on the same 40 acres and close to my house and he uses same cap and its same weather. But time before last when we cleaned out the stove pipe it was wet, watery creosote running down, never seen that before so I think for me the cap may also be causing a problem.
    No catalytic converter on this stove just very simple stove.
    I will definitely now call the wood stove manufacturer to find out what they have to say.
    It’s supposed to get down to -9 tonight and I can’t use my wood stove : ( My son’s going to take the pipe apart again tomorrow and clean it, brush it out again for me.

    Once again, Thank You So Very Much for your informative reply,

  20. Chris, thank you so much for getting back with me.
    An airtight steel building could be problematic, but I have no experience with that type of construction.
    Sorry to keep throwing crazy ideas out at you but, I way thinking where are the cold air returns in a relationship of the wood stove and chimney.
    I once had a stove in a rather tight home and actually had to open the dag-gone front door to feed it air to get started. Kinda blew the energy saving and air tight home concept out the front door 🙂
    I had seen a man install a plastic dryer vent into a small section of an open window, and sealed the other parts of the opening up with insulation to validate that the house was way to air starved (me).
    I agree that contacting the Mfg at this point may provide some additional insights.
    With your persistent and tenacity, I’ll bank that you will get this figured out! You must have done something right in raising your son as your living on the same property and he willing to work to help find a solution. what a blessing to have your son by your side
    …. grab a couple more blankets tonight , 9 degrees is no joking matter.

  21. Hello Clay,
    Just an update… maybe all this will help someone else out when we finally get it solved lol. Thank you for the complement about my son, yes I have 2 sons and I feel very fortunate to be able to say they are both fine men. My son was over again today to clean the stove pipe out again after just doing it on Dec. 8th so in 10 days it clogged back up again (sigh) I had been keeping a window cracked open in the same room as the wood stove and I had been using the creosote pellets every day on the red hot coals. It has been very cold here the last 10 days, highs around 12 degrees and lows 5 – 15 below zero so the stove was burning a hot fire constantly except for when it would die down while I was sleeping.
    Probably because of using the pellets what came out of the pipe was more in sheets than globs, if that makes sense. And nothing, looking like water running down inside of pipes this time – my boilermaker son says that liquid is an acid of some kind running down pipe. .
    After my sons spoke together about the problem, my other son in Georgia who’s a boilermaker suggested this, that since there’s aprox 9 ft of pipe going up, through the attic that, the attic pipe is getting too cold and causing a negative air pressure situation. It is in that area where it’s usually clogged up at. He suggested that I wrap the attic pipe with the proper kind of insulation to keep the attic pipe from cooling off so much. I don’t know if I’ll be able to get that done this winter, it’s up to whether or not my son here is able to do that and when. I certainly can’t change off the cap on my pipe until next warm season comes to see if that helps.
    If we can get the attic pipe insulated this season I will let you know if that makes the difference. If I’m not able to do these things until next year I’ll still remember to leave a message and let you know if the pipe insulation and, or a different cap solves the problem.
    Again, thank you so very much for your help and suggestions.

    Merry Christmas and Happy New Year to you and yours,

  22. We had our woodstove cleaned and inspected several months ago, in the summer. I tried starting a fire today and there was smoke everywhere in the house. This has never happened before. We’ve been here two years, use the stove exclusively to heat our home and have had no problems. The stove is functioning like there’s a blockage – no smoke is escaping the stack outside at all. It was hard to even get a little fire burning today in the box. Cannot see any blockage from inside, but it’s hard to access anything. It feels to me like there’s a possible build-up at the bottom of the stack, right where it connects to the stove inside. Any suggestions? (Obviously, get a professional to look at it again…)

  23. Sara, personally I would recommend calling the service person who you paid to clean the fireplace in the first place. As you mentioned it could be a blockage that they could be easily fixed. As an owner of a service company, I want to know if my customer has a problem,
    especially if we were just at their home for a service call. If they don’t respond to your call or act as though it is a priority, I would then call someone else. No contractor, worth his weight wants bad reviews on BBB, Angieslist or Google or in fact anywhere else.
    Call them back, tell them about your problem and ask them, how can the help you with this before I call someone else to fix this smoking fireplace issue? I believe we all fix squeaky wheels, so may I suggest to you that you to start to respectfully squeak to them about this problem. In closing, be sure to journal each conversation, get the who, when you spoke to someone. My money is on the ideas that they will check this problem out for you.
    Burn Safe and warm

  24. I have a problem not quite like the ones you have addressed. After a small earthquake, bricks from the top of the chimney fell down the flue to a turn in the chimney and are stuck. We have camera’s from the bottom and the top and there are opening and airflow. We also flushed the bricks to get off anything built upon them, but we can’t seem to get them to budge. We can see daylight from below so they are loosely packed. Any suggestion short of going through the wall at the side of the chimney to pick up the bricks. They seem impervious to dropping a weight on them and any harder I worry about damaging the chimney liner. This is a chimney we use for heating via a corn burning stove.
    They are about 16 feet down and 18 feet up. Just cannot figure out something to pick them up with.

  25. I think I the most logical way is to get a mason or a chimney sweep contractor to come out and it cut it out, collapsed bricks is extremely difficult problem to deal with otherwise. Best, Clay. P.S. Just so we always do unclogs from the bottom up.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.