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Old 10-20-2006, 06:02 PM   #1
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Another Leakey Chimney


When I bought my house 34 years ago, it was six years old (built in 1966) and the fireplace and chimney worked flawlessly. Over the next ten years I noticed efflorescence on the exposed side of the chimney, and cracking and winter freeze destruction of the upper bricks. I discovered there was no concrete cap--only mortar, so I installed one in 1985, replacing ten or twenty bricks at the top. This has been quite successful-still intact-made with epoxy concrete and hardware cloth for reinforcement. Unfortunately, I did not use a "floating cap" design and the edge protrudes only 1/2" beyond the bricks.

My continuing problem is from continuous leaking from the outside courses (fortunately!) causing destruction of the bricks over winter, as the temperature in PA goes above and below freezing repeatedly over the winter. I have 4"x12" industrial brick with five holes. The brick composition is volcanic ash/ I believe. I replace larger and larger sections every year, and I have tried to isolate the source--it appears to be leaking at the top courses, and I have repeatedly repointed these--but perhaps not as faithfully and thoroughly as I could have. Last year, I replaced six bricks and this year nine additional. The areas of replacement are all secure, but the efflorescence continues, and is moving lower, destroying more bricks!

I had success with sealing the mortar and bricks over the past several years, but the efflorescence continued. This year, after I repointed and replaced nine bricks, I obtained matching acrylic paint and sealed the entire upper section. Ironically, The areas of effluorence (two) drizzled enough water to wash off two thin vertical streaks, as if to say, "Ha, Ha!"

I have a chimney cover, and upon removing it I noticed that the first section of 12"x12" flue was off center by 1/2" and there was no mortar, leaving about 1/2" of space--which I filled with one liter of mortar. Could this leak have been coming from the inside of the flue all along? Should I replace my cap with a proper cap? should I grout all of the flue joints?

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Old 10-20-2006, 07:08 PM   #2
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Another Leakey Chimney


I am curious about the type of brick you think you have. Volcanic ash is not common and it is not used in conventional clay brick.

Efflorescence is not necessarily bad. It shows you where the noisture is coming OUT of the surface and not necessarily where it is entering. Sealing can contain the water, which will hasten the freeze-thaw deterioration process since the brick may be saturated. You cannot prevent the brick from having moisture in them because of the possible sources of moisture (condensation from heating/cooling, absorption, leakage between the flue lining and cap, etc.).

If you coat the surface so it cannot breathe, the vapor pressure of the freezing process will remove either the coating or the face of the brick. As an example, if you go to the extreme of using an epoxy paint, you will be guaranteed to have all of it and/or the face removed in one year.

A properly sized cap with a "drip line" on your chimney is certainly called for to keep water from running down the face of the brick. Your cap is not adequate.

As you repair the bricks, you are making the surface more impervious forcing the moisture to come out at the lower levels where is is easier to do.

Are the brick fired in a kiln or are they some sort of a cast product? The 12" dimension is a little large for a conventional clay brick.

There should not be mortar between the brick and the flue lining because there must be the ability to move during the heating and cooling. Usually, some sort of semi-rigid material is used to provide support and some sealing. Do not ever grout all of the flue joints!!!


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Old 10-20-2006, 07:18 PM   #3
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My guess would be the flue/cap joint. That is where at least 90% of intact cap problems arise. As Concremasonry says, external sealing of brick will create worse problems than not sealing it unless the water penetration issue is solved first.

Do you get any water/efflorecence at the base of the stack (about 6'-8' off the foundation level)?
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Old 10-20-2006, 07:47 PM   #4
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The flue-cap joint is caulked and sealed. There is no efflorescence below 10 feet (18 feet of chimney above ground, plus 8 feet additional base in the basement level.) That is, the efflorescence is 18 to 22 feet above the base, or 10 to 14 feet above ground level on the first floor. The property slopes, and the basement/garage front entry ia at street level. In heavy rainstorms, there is some leakage from either the chimney or the wall adjacent onto the basement floor. Once I had leakage into the fireplace, but that was eliminated by sealing the brick outside.

Last edited by Jawx; 10-20-2006 at 07:55 PM.
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Old 10-20-2006, 07:58 PM   #5
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Chimneys are tough to diagnose. It sounds like yours is done right. Do you have a picture of the type of brick used?
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Old 10-20-2006, 09:42 PM   #6
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Go to this site:

http://photo.epson.com/


Enter my email address:

jawx@comcast.net


Look under "Chimney"

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Old 10-20-2006, 11:28 PM   #7
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Another Leakey Chimney


Those are called iron spot brick, and there is no volcanic material involved. It looks to me that the issue is the fact the you have too small an overhang on the cap, and then you have the protruding detail right below it. Your mortar looks good; the brick do not look bad. If it were me, I would either form or have made a cap that would extend at least 1" past the decorative protrustion on your chimney and would make sure that it had a 1/4 to 3/8" drip cut into the underside.

I think your problem is the rapid cycle of freeze/thaw that allows water to work the brick and mortar. The flashing is ugly, but probably works OK at the roof line. If you can keep the water from running down the brick, most of your problem will be solved.
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Old 10-21-2006, 07:57 AM   #8
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Thank you, Tscarborough and Concretemasonry, for your advice. It hurts to learn that my flashing is "ugly", since my primary task-this fall-was to improve the appearance of the chimney.

Ironically, this is a total electric home with a 48" functional fireplace which gets used once or twice a year. Actually, it hasn't been used for two years! Since it is an over-all heat loss unless it is used continuously, and it needs to be attended, my wife always seems to nix the idea of fire--after carrying wood in every year! So the Chimney and fireplace are basically for "show". That's why I settled on the paint for the brick. Earlier I had trouble matching the mortar, that is, I didn't have the dark sand. The light mortar looked patchy, and the efflorescenct white patches and streaks looked bad. It looks good now--with matching mortar and brick colors--but for how long? What would you suggest for the flashing? It is 40 year old aluminum and mounted in the brick.

Of course, the structural integrety of the chimney is of prime importance, and six months ago, my plan was to replace the cap as you both recommended, but I spent three days replacing brick and mortar, which created more mess than I had anticipated. Removal of the present cap (3'x5') was more than I was willing to tackle this year.

I am concerned about the mortar in the flue joint. Should I remove it while it is still soft (2 days). What should I put between the flue joints if I still believe there is water entering there?
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Old 10-21-2006, 12:44 PM   #9
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I didn't mean ugly in appearance, I meant ugly from a flashing standpoint. Re: Mortar in the flue joint. So long as you mean mortar between flue tiles, no problem. What ConcreteMasonry is talking about is an airspace between the flue and the brick chimney itself.
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Old 10-21-2006, 12:59 PM   #10
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How could I improve the flashing? And how could I get out the excess mortar I apparently squeezzed into the flue/chimney space. The chimney is actually a single veneer of bricks with skewed brick/mortar/pieces in the 8"-20" between the flue and the veneer. As I have not had the pleasure of building a chimney from scratch, I don't know if that is standard construction for a large chimney. In this case I may have little concern.
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Old 10-21-2006, 09:08 PM   #11
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Another Leakey Chimney


good read guys.

I added a used grate blower with thermostat and rheostat in my last house and actually was able to use the fireplace for quite a bit of heat!

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