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Stains indicate chimney leaks and damage (C) Daniel Friedman Chimney-Caused Stains on Building Interiors, FAQs
Q&A on Chimney creosote, efflorescence, soot, water leak stain on ceilings, walls, floors

Questions & answers on how to diagnose indoor stains at chimneys or caused by chimney problems.

This article series discusses stains in, on or around chimneys and what do these stains mean? Unsafe chimney conditions may be indicated by leaks, stains, or crud seeping out of a chimney connection or a chimney crack.

These articles provide procedures for inspecting and repairing chimney flues - focused on stains that appear on visible surfaces of chimney walls..

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FAQs on Stains on a Chimney Exterior Surface: Creosote, soot, water

Subtle fire clearance hazard (C) Daniel FriedmanThese questions & answers about the cause, cure, and safety significance of stains found on chimneys where they pass through building interiors were posted originally at CHIMNEY STAINS, INDOORS - be sure you review the advice given there.

On 2019-03-29 by (mod) - stains on metal chimney stack?

Melissa

Can you use the Add Image button to post a photo (one per comment) or two of the stain conditions on your chimney so that we have an idea what the problem is?

That would permit more-accurate advice.

If the metal flue is rusted badly it is unsafe and needs replacement.

But we want to know the cause of rust, such as leaks from outside, as that diagnosis can prevent further damage.

Look for evidence of corrosion or creosote leakage at the joints.

Details are at CREOSOTE FIRE HAZARDS

Watch out: also see the safety warnings at METAL CHIMNEY & VENT INDOOR HAZARDS

On 2019-03-29 by Melissa

How do you get water damage off the interior side of a black metal chimney stack

On 2019-01-14 by (mod) - bees wax seeping out of chimney

Anon

You asked the same question and we replied at

CHIMNEY CRACK DETECTION & DIAGNOSIS - please take a look there and don't hesitate to ask if you have further questions.

On 2019-01-14 by Anonymous

Something like bee wax is seeping through my chimney stack upstairs and coming through the paint and dry wall

On 2017-01-09 by (mod) - chimney people didn't find a problem but water drips out of wall above fireplace

I'm sorry that your chimney people didn't find a problem, because what you described certainly sounds like a problem to me.

From the history that you give I suspect that the chimney is damaged, perhaps cracked and leaking. Most likely there is either outside water leaking into the chimney or building air is leaking into the chimney leading to condensation accumulation of frost and perhaps sometimes melting frost that shows up as water or condensation back in your fireplace into your wall.

See if you can find a certified Chimney Sweep who uses a Chim scan camera to inspect the flu as well as performing a thorough inspection from outside.

On 2017-01-08 by Matt Beck

The painted wall above my fireplace has water (humidity) dripping.

The stack in on the outside and not going into the attic. I have a damper on the top, closed for winter.

Also the glass doors on the fireplace are covered in water too. Always had a little but not big this extreme. Had previous issues with the chimney, smoke entered house and stunk it up when used.

Many chimney people out and found no issues. So we don't even use the fireplace anymore.

Question: rotting at the chimney?

(Feb 8, 2014) Hope said:

I was in the attic where I noticed an area on the chimney that was darkest and looked like it was rotting an the chimney shoul I be alarmed for possible chimney fire?

Reply:

Hope,

Without knowing what the chimney is made of, what it is venting, and what you saw, I could only GUESS that you may have seen brown stains on a masonry chimney that may be a creosote leak - indications of several unsafe conditions if that's the case.

To be safe you should call a certified chimney sweep and have the chimney interior and exterior inspected for safety and function. Let us know what you are told, and send along photos if you can and we may be able to comment further.

Use the CONTACT link at page bottom or top to email photos.

Question: screw through wall punctured metal flue - is this safe?

12/17/2014 Karen said:

Our fireplace is a Heatilator TD42B. We recently installed a heavy scupture on the wall above the fireplace. One or more of the screws holding the sculpture were inserted through the sheetmetal in the flue.

We thought this would be okay since the screw would plug up the hole that was made. The next time it rained, water started leaking through the wall and through the top of the fireplace above the doors. How could water be getting in there? We had a roofer inspect up on top, but he couldn't find a problem.

Reply:

Karen

Watch out: In my OPINION, the hole made in your chimney is a fire and safety hazard, even though it may, at initial puncture be small and partly sealed by the puncturing screw.

My understanding is that the Heatailator TD42B can burn wood logs. Log burning can, depending on how dry the logs are, produce both creosote and other moisture in the flue.

If you were burning gas logs the probability of condensation in the flue is even greater.

Water might also enter a flue if a chimney cap is an improper design or is improperly installed or if it has been damaged.

Water might also enter a flue from any other damage anywhere along its length, or from a poorly constructed or poorly-sealed steel top flashing around a wood chimney chase - I can only guess as we don't know how your chimney is installed.

I understand that it could seem like an absurd amount of trouble to fix a screw hole leak, but for safety my advice is that you ask for help from a certified chimney sweep in assessing and repairing the flue as well as checking the cap and the condition and safety of the flue interior.

It MIGHT be possible to seal the opening with solder or another high-temperature sealant but unfortunately in my experience, everyone around such a project is so afraid of liability that no one wants to touch a "non-standard" repair. This is so even if on their own home they'd take that risk.

As it's rain-related, before just sealing the opening or replacing that flue section (as required), I'd get a more expert inspection of the chimney cap, chimney top seal or flashing, and I'd look for leaks along the chimney run.

More advice is available from the Heatilator company's technical services department. That contact information along with a link to the installation manual for your Heatilator fireplace is just below.

Question: black stuff oozing through mortar on our stone masonry chimney

(Feb 1, 2015) Debi said:

I have a stone mason fireplace with a gas starter and logs. The fireplace anchors the end of a vaulted ceiling where squirrels have been lifting the roof ridge next to the fp when it gets cold and getting in the small crawl space since there is no real attic.

There is a black slow oozing stain on the mortar about a foot down from the ceiling where this is occurring

. I called someone with experience with Chimneys and he said he thought it smelled like excrement from the squirrels.

I then called a roofer who told me my chimney top was flat when it was supposed to be rounded and he thought water was getting in-between the brick and the flu and it could be black mold because it couldn't be creosote since it was gas and that the squirrels were relieving themselves on the roof.

I have a call in to someone to come test for black mold, but after reading your article, it seems that would be unlikely. I can get the fireplace fixed and the roof line fixed, but I don't know what the black stuff is, if this will take care of the problem, much less how to clean it off the mortar.

Just in the last couple of days, a new spot has appeared adjacent to the original 8 inch drip. H E L P~

Reply:

Debi

Watch out: The black stuff is typically creosote or creosote mixed with condensate since you've changed the fireplace ( I suspect ) from wood to gas - which itself is an unsafe thing to do without expert chimney inspection, cleaning, and if necessary, repair or re-lining.

So just cleaning the stuff off comes after the safety worries.


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