Asked on Jun 21, 2012

soot or creosote on chimney exterior?

Sw E
by Sw E
Soot on exterior of chimney, not only on the cap, but rain washes it down to vertical pipe and the pan. Runoff from the pan carries it down to the stucco below and we can't get this stuff off! (Chimney or stucco)
Any ideas for how clean off the soot in the first place? Ideally I could clean the top of the vertical pipe and the pan, that would reduce the soot running off the stucco anyway.
Have talked to a contractor about this. The pan has to be replaced anyway, and he will put in a new one with slightly larger overhang to help reduce the washing down onto the stucco. But I would like some advice about the soot and trying to prevent it or clean it up in the first place.
Contactor offered to paint the vertical pipe, that would give us a fresh start there, but should I ask for a specific kind of paint? If it is painted I need to be able to clean it off anyway?
I could ask the contractor to also replace the top cap, but I don't know how much this will help the soot / creosote problem. Cap is otherwise solid not rusted out and seems to keep the rain out.
Lastly we will repaint the stucco. But I need advice because I can see that the soot will just keep on washing down, eventually darkening the new coat of paint on the stucco. So I hope you can advise me on ways to clean this properly, or perhaps prevent soot from washing down from now on.
  7 answers
  • It appears that you have a hard coat stucco finish? Your not going to get the stains out. You need to paint the stucco with a fresh coat of elastomeric paint that is designed to be used on stucco. This type of paint breaths which needs to be done to prevent stucco damage from trapped moisture, and it has a flexible finish so it hides cracks and bridges over them without re-cracking again. Now the chimney. You are correct you do need a new pan, it should fit tight but can have a lip of sorts along the bottom to prevent any drips from running down the top surface of the chimney wall. To help prevent this from happening again, you need to address the height and type of chimney caps you have. Two chimneys next to each other should NEVER be the same height. This causes down drafts when one or the other is being used. In addition the type of chimney cap you have will prevent the gasses from escaping as smoothly as they should. This added friction will clog up the chimney draft thus allowing additional soot to develop. Lastly you need to stay on top of your chimney cleaning. Burn better quality wood. No pine, or sap woods and no pallets or lumber. Truly your looking at several years of this building up. This is not something that develops in one year, unless you burn a lot of wood seasonally. And if that is the case, you need to check the inside of the flue for creosote build up at least once a month. If you have not done so, be sure to find a chimney sweep that is a member of the National Chimney Sweep Guild. These folks are of a higher standard and can offer all sorts of great advice on maintaining this chimney system to help prevent this from occurring over and over again. Chimney systems and designs are very complicated so you need to be sure your doing the correct thing so not to burn down your home.
  • Sw E Sw E on Jun 22, 2012
    Thank you for the reply. The stucco has elastomeric paint, and we are generally happy with the paint. We are expecting to repaint, because we have found nothing (wire brushes, or cleaners) which will remove this soot. Repainting will not be a huge difficulty, and aside from covering up this ugly soot, doing the repainting also provides good coverage for micro-cracks in the stucco, improving the protection. BUT what bothers me is that we might continue to have soot problems, soot building up on the pipe and the cap, then washing down onto the stucco. I want to clean it up and prevent the soot at the source! Any suggestions welcome!
  • Sw E Sw E on Jun 22, 2012
    Thanks for the answers, but I'm still hoping for more ideas.
  • You are not going to stop the soot completely. You can control it better however using a better type of chimney cap on top. There are those that vent upwards. The ones you currently appear to have push the smoke out sideways. This contributes to the soot development both on the pipe and chimney itself. Doing the new metal chimney cap itself with another lip along the bottom will help prevent the soot from running down the chimney, but once it drips onto the roof below it will being to build up on the shingles and then run down them when it rains. Depending upon the color of your roof, this may also be objectionable to you. Your not going to get all of the soot off of the siding. The surface of the stucco is porous and will trap this stuff within it and all the wire brushing and scrubbing you do will not remove it. You of course in part of prep for the new paint will need to clean the walls of the chimney prior to painting, but do not waste your time trying to get the color of the wall to come back by simply cleaning. Not going to happen. I would seek out the advice of a pro chimney sweep as I suggested in my first answer. Not seeing the height of the chimney and knowing if there are other issues at play such as higher roofs, valleys and prevailing wind conditions it is impossible to answer this any further. Perhaps a distance shot of the chimney showing the ground up to the top of the roof with the chimney in the photo? That may also shed some light on what is going on and perhaps offer up some other ideas that I did not talk about once its seen.
  • RockfordChimneySupply RockfordChimneySupply on Mar 19, 2013
    Have you looked into installing a new chase cover? If you install a stainless steel chase cover it will never rust.
  • Sw E Sw E on Mar 25, 2013
    Thanks Rockford, but we have three chimneys, and even though this one has the worst soot problem I think if we installed a cover on one we would go for the same treatment on all three. In addition, there is the visual look of stucco to consider. Because we have stucco, and long surfaces/walls, we would have to stop the cover at some point, and have a boundary between the new chase cover and the stucco wall. The cover shown in your pics doesn't give me much confidence that the cover will blend in well to a stucco wall/chimney base.
  • Se W is the chimney high enough? Normally the soot is removed from the chimney, however if the chimney is located to low below a roof line down drafts can push the soot down at a greater rate. Ideally the chimney should be at least 2 feet higher then anything within a 10 foot circle around it.