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Old 01-13-2007, 11:57 AM  
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Default Fireplace Brick Problem

We are having problems with a white substance leaching through our fireplace bricks. Since we live in Seattle which is known for its precipitation, I'm wondering if this might be the cause of the problem.

The bricks are clear, unpainted bricks. My wife washed them, the the same white material was back in a week.

Any advice as to how this can be treated and prevented would be greatly appriated.



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Old 01-13-2007, 11:20 PM  
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The way I understand it this is lime leaching out of the mortar. I would think there has to be water creeping through there to do that. Therefore, I would check the flashing on the roof, put a full sheet metal cover on the chimney and spray the rest of the exposed chimney (outside) with several coats of clear silicone, and repeat the spray every 6 months.

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Old 01-14-2007, 02:07 PM  
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Take a hard look at the crown of the chimney. - The concrete placed on top of brick that should shed water off the chimney. Make sure there is not a gap between the chimney flue and the concrete.

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Old 01-14-2007, 06:33 PM  
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Default Efflorescence

that's the ticket!

Google it

no rain in WA, has not rained here in like, 2 weeks
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Old 01-15-2007, 06:33 PM  
Bud Cline
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This white substance is known as efflorescence. It can be caused by lime or natural salts that exist in the portland cement.

Moisture is activating the salts and evaporation is bringing it to the surface of the brick. It will play out over time but that could take years.

Find the source of the moisture and correct it, the leeching will subside and can then be cleaned away one final time.

If the chimney is not capped, cap it with an oversized cap that will prevent blowing rain from coming down the inside of the chimney. Also look for other sources of moisture. Bad flashing to roof, missing or loose mortar between the bricks, cracks in the mortar, soft brick makeup, anything that would allow moisture in to the chimney materials.

If no obvious source of leaking can be found then seal the bricks and mortar on the outside thoroughly.

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