Damp Chimney Breast/Porous Stack/???

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Hi all,
Been having something of 'mare since moving in a recently bought 50/60s bungalow. Previous lot hung a big picture on the chimney breast, and now I know why! Been around the houses on this and any thoughts would be great:

1- When stripping back walls, pre-decorating, we revealed big dark patches on the plaster in a couple of areas on chimney breast.
2- The breast was opened up to install a wood burner and the hope was not having trapped air/moisture may help - but of course it didn't.
3- We ripped out a big patch of plaster, treated bricks with salt neutraliser and redid the plaster with damp proof additive. No joy.
4- Couldn't afford to delay plaster skim, had to go ahead. The below shows the areas taking longest to dry, which eventually dried and then un-dried after rain. The stuff in the centre isn't as clear as it gets after rain, but you can see the areas we had the plaster hacked out and replaced. Note the area on the ceiling, which correlates to the area the chimney stack 'juts out' above.
20170923_142703.jpg

Loft:
20170927_205511.jpg

4- Further investigations in the loft ... long story short... we found that when it rains the bricks in the chimney stack (or rather, I assume, mortar?), 'seeped' moisture. The ceiling board is very high on a damp-meter as are all the bricks that are nearest the 'jut' in the chimney stack.

At this stage it seemed there must be some penetrative moisture getting in rather than it just being condensation and salts etc.

5- We had the pointing above roof level checked and given the thumps up, a few broken tiles replaced and flashing reattached. None of this helped the situation with the plaster down below.

The below is a picture of the ceiling board from above - i.e. in the loft. Gross, but mouse poo aside (another issue I'm dealing with) you can see the damp board, and wooden beams which are damp (wetter at the top than the bottoms)...
20171014_104207.jpg


...OK... so any thoughts?!
I'm thinking of the next step to be repointing the loft part of the chimney stack. It's clearly a problem, and it seems too much of a co-incidence that this is the area below the jut in the stack to not be linked.
However... there's still moisture getting down to it inside the chimney it seems (I've observed a few times during rain and there's been no internal leaking, though some signs that may have occurred in the past.)
Porous bricks all the way up and down? Anything to be done? ...I've spent too long sat staring at it, losing my marbles now.
Cheers
Patrick
 
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do you have cowl on the top to stop rain falling down the stack?
 
Should added that, yes, cowl is in place and in good order.
 
so the cowl has a cap that prevents rain entering. the chimney is cemented round at the top to seal the cowl and liner the chimney pointing above roof is ok. the flashing and surrounding tiles or slate is good and yet even now the damp goes darker when it rains?
 
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That's right - though I'm trusting a couple of different work people who have been up on the roof. No reason not to, really. But my hunch is still that there must be a way for moisture to be getting in up there. The darkening seems very much linked to rain.
 
to me it looks like inside of the chimney is getting wet then its just soaking through. I think you need a second opinion on the integrity of the stack above the roof. it could be old damp coming through as it will take months to dry properly but obviously should not now get worse with rain.
 
if its a joint stack with next door did your guys check that side too
 
Has the lead tray been correctly installed with weep holes above it and if it is visible in the loft, has it been turned up the stack to deflect water out?
litl
 
Excellent question - I'm awaiting a ladder to arrive so I can get up and have better look at the chimney. From ground level, I can't see anything that looks like a DPC or tray, but no idea if they are always detectable from the outside, just seen a few examples on google image search with a flap of DPC poking out.
chimney1.jpg

chimney2.jpg
 
Your pointing looks pretty rough. Someone has cemented the blown brick faces and presumably repointed (badly) at the same time.

Is it possible that the pots have developed gaps where they meet the flaunchings?
 

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