On 26/02/2021 21:18, alan_m wrote:

It's not obvious how that tall mast is secured but perhaps its not doing
your chimney any favours as you also seem to have cracks running through
the centre of bricks.


Actually it's possibly not a structural crack but part of the next brick
about to spall but the flake of brick is being held on by the paint.

New paint may prevent water entering the surface of the brick but old
paint that is failing may let water in behind the paint layer and then
prevent it from evaporating. One problem with painting a wall/brickwork
to prevent water ingress is that regular maintenance is then required to
maintain the paintwork.

There is another section further down the chimney that is showing
failing paint, probably because the brick behind is also spalling.

If that chimney is to be repainted a repair could be attempted by first
removing any obvious failing paint. Soak the surface of the bricks that
have spalled with a water seal and use a sand cement render just to fill
the missing surface layer on those bricks - then repaint. Possibly rake
out and replace any dodgy pointing which may also let water in to the
top of the brick. I did this 30+ years ago on my current house for a few
bricks that had minor surface spalling and have noted no further
deterioration or failure since.

Water Seal
https://www.wickes.co.uk/Wickes-Wate...---5L/p/600336

If you are not going to DIY consider getting in a company that use
alternative surface coatings that are meant to last maintenance free 25+
years. Or, as others have indicated, in not used remove the chimney
above roof level.


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