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The chimney in my 50 year old house, which serves the furnace and water heater, cuts through the gable end of the house. One side is exposed, the other side inside the attic. On the attic side there is some kind of white stuff all over the mortar joints around the bricks. It’s very fine, reminds me of the dry joint compound that comes in a bag. Around the base of the chimney where it hits the attic floor, the stuff is piled up about 2 inches thick. Is this something caused by the flue gases? Should I be doing something to remedy this? On the outside of the house and in the basement there is none of this stuff on the chimney.
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Efflorescence? Kind of surprising to think that it might pile up to 2 inches thick. Or is it ash that blew out through a hole? Efflorescence should clean up with a mild acidic cleaner.
*I was project coodinator on a large commercial addition a few years ago and the design architect was adament about possible effoesence problem in the future if the brick veneer was not properly vented and weeped. I've seen brick that effores when it traps moisture and then freezes. You might want to look at you top cap for cracks or loose motar where water can get into or behind the brick. since the only place you are seeing is in a cold attic area I would suspect that may be the cause. Also check the step flashing where it is tucked into the brick.
*Sounds like efflorescence to me, too, but it's a b huge amount. I see a lot of houses and a lot of efflorcesence, but I've never seen anything like that.I strongly recommend having the chimney checked out. It's possible that there's a crack or hole in the flue liner and that water vapor in the flue gases are condensing and getting out of the flue and into the chimney mass. If that's the case, flue gases might be getting into the chimney and attic area as well.Not likely, but possible. Is the any spalling of the brick face on the exterior portion of the chimney?
*Thanks for the advice, I will have someone take a look at it. To my untrained eye, the brick on both sides of the chimney and the mortar seem to be in good shape. I thought efflorescence was kind of a stain that went away after a while. This stuff seems to be accumulating around the mortar joints until it gets so thick that it falls onto the attic floor.
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The chimney in my 50 year old house, which serves the furnace and water heater, cuts through the gable end of the house. One side is exposed, the other side inside the attic. On the attic side there is some kind of white stuff all over the mortar joints around the bricks. It's very fine, reminds me of the dry joint compound that comes in a bag. Around the base of the chimney where it hits the attic floor, the stuff is piled up about 2 inches thick. Is this something caused by the flue gases? Should I be doing something to remedy this? On the outside of the house and in the basement there is none of this stuff on the chimney.