Chimney stack

[Bob D]

The chimney Stacks on my 1911 property have been reduced in height in the past..
Could the fact that they no longer comply with the 3 2 10 rule be the reason for damp on the disused chimney breasts.
They are not capped and have an internal air vent , but experiencing very poor updraught to deal with condensation.

 

[a twig]

I would generally look to jackdaw nests etc as the primary cause

 

[Bob D]

The chimney pots have cowls on , what i should have said was....
The unused chimneys have not been capped off but have cowls on.

 

[a twig]

Still worth checking, chimney may not have been swept before cowls were fitted, and jackdaws often persist in still forcing sticks in even if they can’t get in themselves. You can buy a cheap usb boroscope from the usual suspects online, with sticking that in and having a nose around.

In answer to your question yes the reduction in height would reduce updraft but you don’t need a howling gale to ventilate an unused one so I’d be surprised if that’s the cause, with chimneys it is more likely to be failed flaunching / pointing / lead work etc.

Alternatively it could genuinely be condensation - the breast being colder (due it it being single skin) than the rest of the walls so moisture in the air internally is condensing on that wall

 

[Bob D]

Ordered a scope yesterday , and pointing is on the list to do, when weather improves
Thanks

 

[Lacan07]

The chimney Stacks on my 1911 property have been reduced in height in the past..
Could the fact that they no longer comply with the 3 2 10 rule be the reason for damp on the disused chimney breasts.
They are not capped and have an internal air vent , but experiencing very poor updraught to deal with condensation.

where's the damp occurring, is this on the breast on the upper floors or lower floors? Is it internal or external wall?

 

[Bob D]

Upperfloor internal chimney breast...

 

[Lacan07]

Upperfloor internal chimney breast...

Where is the damp occurring on the breast, have you been up to the loft to investigate beyond the ceiling?

 

[Bob D]

It's in patches on the chimney breast and I've been in the loft which seems OK.

 

[stuart45]

Hygroscopic salts are often an issue with condensation on the chimney breasts.