On 27/02/2021 09:39, Muddymike wrote:
On 26/02/2021 21:03, AnthonyL wrote:
What is happening to my chimney stack bricks and why?

https://flic.kr/s/aHsmUwRSEW

It is a non-working chimney though I don't know if that has always
been the case.

How do I fix it?

Cheap bricks tend to do that. Rebuild with better bricks is the only
permanent solution.

Mike
engineering bricks