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Why is this brick eroding?

rhoganii | Posted in General Questions on

I have an interesting thing happening to my brick chimney. We noticed that two of the bricks, their faces, kind of crumbled off. Not the white powdery residue but actually powdered off in the same color as the brick. Looking for a reason why this might be happening. We live in Missouri (St. Louis). In the pictures the picture labeled “Brick 2” is what the effected brick looks like. The other picture is a typical smooth brick on our chimney.

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  1. GBA Editor
    Martin Holladay | | #1

    These may simply be old bricks that were not fired properly -- weak bricks that aren't durable.

    Or the problem may be due to an oversized flue (leading to corrosion caused by flue gas condensate). For more information on the latter problem, see When a Flue is Too Big.

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