Aren't Chimney Bricks Supposed To Be Solid?

Up on the roof, there was a rectangular slice of brick. The rest of the brick, still in the chimney, felt as if it could be scraped away just with your fingertips. A second brick in the chimney has an outer slice also ready to fall off.
Ever hear of such a thing? Causes? Cures? Thanx.
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Water and N.G. damage common , get a few bids
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snipped-for-privacy@webtv.net (m Ransley) wrote in message

The chimney should have a flue liner to keep the combustion products away from the bricks and mortar. Without one, over time, the acid byproducts of combustion will deteriorate the chimney and cause a potentially serious condition, where flue gasses can enter the home. Older homes typically have a ceramic one. If you don't have a liner, there are stainless steel ones available that can be inserted inside the chimney, after it's repaired.
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