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Old 11-21-2008, 09:20 AM   #1
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Damp wall by chimney


If anyone can help I have the chimney in my house (built in the 60s) running through the master bedroom. The wall and chimney have been plastered over and painted. Whenever we get a heavy rainstorm it almost seems like the bricks bleed or sweat and moisture comes through and causes paint and plaster to bubble and sweat. The roof has been redone as has the chimney I am willing to rip plaster of but how do I solve the problem.

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Old 11-21-2008, 09:50 AM   #2
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Damp wall by chimney


I would suspect that the chimney isn't flashed properly at the roof or you are not getting good drainage off the roof and water is backing up around the flashing.

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Old 11-21-2008, 10:01 AM   #3
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Well i guess that could be it but I had the same problem before I had roof redone and chimney tucked and pointed there doesnt appear to be any pooling and problem still exists and it mainly occurs after ba really heavy driven rain.
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Old 11-21-2008, 04:00 PM   #4
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Damp wall by chimney


Did the roofer redo the flashing detail around the chimney or reuse the existing? If the flashing detail wasn't correct to start with, a new roof wouldn't necessarily solve the problem. A good roofer should know how to build a good flashing detail along a chimney. A shingle pounder may not. If it only happens during a wind driven rain, then my first look would be at the flashing detail. See the detail at the bottom of the page in the link.
http://www.extremehowto.com/xh/print...ticle_id=60348

Sometimes roofers take a shortcut and reuse the flashing that was in place because it looked good. What they don't take into account is that when they reroofed they nailed it in a different place. It now expands and contracts differently than it did the previous 20-25 years. Sometimes the flashing will then crack or tear out. In a lot of places the counter flashings are incorrectly or never installed leaving the edges of the step flashings exposed to wind driven rain. Inspect it closely.

On rare occaisions, I've seen porous brick absorb enough water that it would show up inside if under wind pressure. Coating the brick with a siloxane water repellant will help. Make sure all of the mortar joints are tight.

On a dry day, take a hose and starting low on the roof wet things working higher until you see water penetration inside. Don't spray up under the shingles, but try to simulate how water would naturally fall on the roof. The idea is to recreate the leak under controlled conditions where you can see what's happening.
If this chimney extends through an attic space look in there for clues as to location.
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Old 11-21-2008, 08:46 PM   #5
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Damp wall by chimney


Well Ihad someone inspect flashing and it was all good, It was a high end roof company, It really seems more like the moisture is coming right through the brick. Anyways I guess I can rip all the plaster of and clean up brick and see what I end up with.
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Old 11-21-2008, 09:20 PM   #6
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Damp wall by chimney


Moisture barrier in your wall not working right?
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Old 11-21-2008, 09:32 PM   #7
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Damp wall by chimney


Is you heater venting through the chimney?
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Old 11-22-2008, 01:55 AM   #8
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Damp wall by chimney


Allan:

Go to where your furnace or boiler and/or hot water heater are and look where the flue gas duct off the furnace or boiler or hot water heater connect to the chimney.

That will NOT be the bottom of the chimney. The flue ducts will connect to the chimney several feet above the bottom of the chimney. The chimney will extend down several feet, where there will be a "Clean Out Cover" on the wall.

The purpose of this Cover is so that you can remove anything that falls down the chimney, like leaves, or bird's nests or even bricks.

When gas burns it produces MOSTLY CO2 and H2O. That H2O forms condensation on the inside of the chimney. When condensation forms in a high CO2 environment, the condensate will have lots of CO2 dissolved in it. When lots of CO2 is dissolved in water, some of the CO2 will actually combine chemically with the H2O molecules to form H2CO3, which is carbonic acid, which is what gives carbonated soft drinks their acidic "bite". That carbonic acid will attack the mortar between the bricks on the inside of an unlined chimney. When that happens the mortar is dissolved, and the resulting sand falls down the chimney and collects in the clean out space below where the flue connects to the chimney.

Go take your clean out cover off and see how much sand there is in it. If there's a lot of sand, that means that there's a lot of mortar missing between the bricks on the inside of your chimney, and the rain water might actually be flowing THROUGH the bricks on your chimney and getting the insulation and plaster wet below the roof line.

Do you have a rain cap on your chimney?

PS:
It's a REAL GOOD idea to take your clean out cover off once a year and hold a mirror inside the bottom of the chimney. Angle the mirror so you can see up the chimney. If you can see what looks like a light at the end of a tunnel (the sky) then it means your chimney isn't blocked. It's not uncommon for a chimney to get blocked for some reason, with the result that the boiler, furnace or hot water heater starts producing more and more CO instead of CO2. Here in Winnipeg, chimneys have to be inspected every year, and part of that inspection is (obviously) to check that the chimney is clear. There was an apartment block in Winnipeg that had a blocked chimney and an entire family died of CO poisoning.

Last edited by Nestor_Kelebay; 11-22-2008 at 01:58 AM.
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Old 12-03-2008, 12:17 AM   #9
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Damp wall by chimney


Thank you<
I will check that out
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Old 12-03-2008, 12:19 AM   #10
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Damp wall by chimney


Quote:
Originally Posted by hostchecker View Post
Moisture barrier in your wall not working right?
Could be but I guess I will have to rip down the wall to find out.

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