Damp stack

[footprints]

Hi all,
Just wondering if it is at all common for old stacks to become porous.
I have damp around the chimney stack on the ceiling (plasterboard) and the wall at ceiling line on the staircase backing the stack.

I had the listings and lead soakers replaced about 6 years ago, the pointing looks in good nick but the render in the loft is very poor and crumbly.

I know there could be a problem on one side as the old gas boiler was flued up the old unlined chimney to a GC1 alli terminal at the top. When the boiler was replaced the terminal was not capped and no vent provided behind the boiler which was fitted in the same place.

Now i know this could be a problem but, the other two chimneys mid and right have good ventilation, an open fireplace in the lounge with a bit of board to catch debris with a full width wide gap left at the back and a vent in the boarding in the bedroom. They are equally damp though.

Anyone got an opinion please?

 

[vinn]

If you dont mind my replying I'll do my best?

You have two chimney breasts and two stacks with two flues in each stack - four fireplace openings in all? Or do I have that wrong?
Are the flues definitely open or ventilated somehow top and bottom?
When were all the flues last swept? If its an old house then when last smoke tested?
All flues are free from liners or appliances? Solid fuel fires are not used?
Photos of all the chimney stacks might help - I'm looking for external c/breasts and perished stacks/flaunching/flashing & abutting roofing.
A photo of the stained ceiling would be good?
What are the "listings"?
When convenient its best to replace the old GC1 with a clay terminal.

 

[footprints]

Thanks for replying vinn.
One chimney three pots.
Two, the middle and one end are open.
The third is closed at the bottom end but has the gas terminal on top.
Both open flues were swept when I moved in 10 years ago and no solid fuel used in them since.
All were clear and I smoke tested all three to check which was which.
The gas one was obviously clear as till 2 years ago the gas boiler was using it.
Listings are tiles cemented flat to the sides to give a neat and water shedding trim against the roof with lead flashing underneath (according to the last roofer).
You cannot see the gas terminal (third) from the ground, but it and the flaunching are in good nick.

 

[vinn]

Thanks for the photos.
Now I know what Listings are.
They are not a good idea to my mind, and I've only seen similar arrangements as an alternative remedy for dealing with leaking or non-existant flashings.
You do have lead flashings below the listings but the lead flashings are wrong.
Lead soakers should be positioned below that type of tile, and lead cover flashings should come down over the soaker upstands - just like on slate roofs.
The ridge to stack abutment should be straddled with a lead saddle.

The flaunching and a possibly degraded Alu GC1 are still suspect but given that the bedroom photos show damp thats presumably come down the face of the loft chimney breast I wonder if its not all coming through the listings/flashings?

The damp in the photos looks recent, and no particular staining can be seen. When did you first notice any damp?
What are the other damp areas like?

 

[footprints]

We had some staining in the bedroom ceiling similar to the stairwell (which is where the staining is now) when we moved in and that's why the listings were done.
The staining on the ceiling on the stairs is very recent only noticed a week or so ago but the line of damp across the whole stack at ceiling level has been in the last 6 months or so.
Damp meter anywhere on the stack in the loft goes off the scale but all the timbers around are giving dry readings, no drips from the roof itself.
The side that has the damp at ceiling level is west facing so gets the prevailing wind and most weathering.

 

[vinn]

Given what you report, I'm not certain but I'd suggest that you have nothing to lose by removing and remedying the listings/flashings with lead soakers and cover flashings.
I'd guess that its a strong possibility that moisture is creeping under the incorrectly fixed flashing.

Without photos of the flaunching and terminals its difficult to have views about that area of the stack?