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Hi... hope someone can help... I've uncovered some damp on the chimney breast in an upstairs bedroom... the chimney is external and the patch had 'helpfully' been covered by a metal plate before being papered over.... the patch has been there for, I'm guessing, 20 years plus... I thought it was flashing needing to be replaced but the roofer I had round said the chimney stack was saturated and it needed to be taken down to below roof level... he said if the flashing had gone the water would be running down the wall... is he just trying to make a big job out of a small one? If the stack is saturated does it have to be removed or is there something that could coat it?
thanks

a stack only ever needs to be removed if its structurally unsafe, if he hasnt mentioned anything like this i'd be wary...
any brickwork exposed to the elements is going to soak up water unless its sealed, and then it cant 'breathe' i.e. 'dry out again once its gotten wet'...
in the days when the stack was used the heat would dry it out and damp would not be a problem..
stop using the stack/flue/chimney and its going to soak up water...
this water will then work its way through the brick(s) via capillary action, so its perfectly possible its shown itself below the roofline...
so how to stop it?
1) vent the stack and prevent any water coming down the middle of the stack - vent all flues at fireplace level and cap any pots with a 'chinamans hat' style cowl that will stop any water coming down but allow free airflow withing the flue...
2) do check all flashings... older flashings may be done in code 2 lead which is too thin and may tear, also slate roofs use 'soakers', used to be made from aluminium which unfortunately does corrode over time, a long time, but they do need replacing eventually and a small hole wont have water running down the wall, just a big damp patch as most of the water will soak into the bricks...
a big hole will have a very wet ceiling too but i have honestly never seen 'water running down the wall' from failed flashings, maybe a light drip... there would need to be no flashings at all, no felt and one hell of a downpour
3) repoint any deteriorated mortar joints and any cement haunching on the top, obvious but nessesary...
4) in the absense of a 'cavity tray(figure of speech in this instance, lead dpc would probably be more accurate)' to stop water soaking through the bricks into the house then a proprietory 'masonary water seal' may be sprayed on in two or more coats to help seal against water ingress...
this will hinder the bricks from breathing but will stop any further ingress to a point...
as long as the bricks can 'breathe' from the inside of the flue its usually ok...
5) dont expect it to dry overnight, it can take months... remove all damaged internal plasterwork and leave for as long as possible with plenty of 'through ventilation' before replastering with sand and cement containing a waterproofing additive followed by a skim coat.

its still not a tiny little job doing all that, days work easily, possible chimney scaffold depending on the height of the stack from the roofline..

removing a medium sized stack below roofline is also a days work, maybe 2, extra skills and manpower, with a chimney scaffold and a skip, and the risk of masonary tumbling down the flues and blocking them...

just to be on the safe side i'd get another quote in from another roofer, the stack may well be unsafe, a lot get hit by lighning over the years and develop cracks right through the middle, ive removed stacks that have almost split in two and been 8 potters, 8 feet off the ridge, nick of time...

Thankyou so much... I did think it sounded a bit drastic ... a second roofer came and he said the stack was in good condition and it was the back guttering... I'll ask for the capping too ... thanks again... btw when you say 'vent' does it count if they are fully open fireplaces at the bottom of the stack or should i still put vents in?

if theyre open fireplaces and you have a 'draw' or draught going up the chimney flue theres your ventilation...
if the flue is blocked with a peice of board or similar youll need to cut a hole in the board and stick a louvred vent over...
its all about the 'flow' of air, simply venting the top or the bottom wont suffice, you need to get air to flow through the flue..

chrisw w wrote:if theyre open fireplaces and you have a 'draw' or draught going up the chimney flue theres your ventilation...
if the flue is blocked with a peice of board or similar youll need to cut a hole in the board and stick a louvred vent over...
its all about the 'flow' of air, simply venting the top or the bottom wont suffice, you need to get air to flow through the flue..

thanks