CMU chimney, mortar joint deterioration

Top three mortar joints deteriorated, the rest OK.

Owner stated that they remodeled the fireplace face this summer after deciding to put it on the market.
My theory is that the chimney was originally too low and didn’t draw well, so there was some smoke damage on the face of the old fireplace and mantle. At some point one cold winter they had a new fireplace installed and the installer said “hey, chimney’s too low, that’s why it smokes!” so they extended the chimney. During the winter.

The mortar froze before it cured fully and so was weak and subject to accelerated weathering. That’s my theory, anyway.

Thought I’d add the bighorn lambes and ewes. They ran accross the road in front of me on the way there.

I would think it needs to be touched up and tuck pointed.

Hard to say from Tucson.:wink:

Yep, raked and repointed.

Good catch on a snowy roof. Be careful and by all means have fun.:smiley:


While your hypothesis may be correct but without factual documentation.

Who know?

If you are not trained in chimney evaluation I would defer to an expert, as I’m sure you did.

The majority of masonry chimneys I see that have deterioration have it occurring at the uppermost portion of the flue, crown, and cap configuration as in your example of the upper three courses.

Most are related to moisture intrusion from a failed crown or cap and possible design anomalies.

Further information may be found here:

Kenton, I see you did a favor to your client and shoveled his porch for him.

That was pretty nice of you. :wink: :slight_smile:


Build them right and you won’t have this problem.
I’ve only seen one.

Nope, -X
I’m the guy behind the camera, Marcel. The client breaks trail and does the shoveling. I’m the guy who takes pictures and tells the shoveler “you missed a spot” :|.)

Build them right and you won’t have this problem.
I’ve only seen one.


That’s a good one Barry, thanks.

I told them it appeared to be freeze damage, but my recommendation was for a qualified masonry contractor to rake the joints and re-tuck.](“”)