Damp patches on upstairs chimney

Jo2107 · Post by **Jo2107** » Thu Oct 22, 2020 8:00 pm

Sorry for another post! A few days ago we noticed the patches seen in the photo, any idea what could have caused them?!
There is a small vent above floor level that had been closed for a few months, room regularly used and kept warm. We have a log burner which has a flue. Could it be damaged pointing on the chimney? There might be the odd damp patch in small sections of the chimney in the loft, but hard to be sure. No leaks from the roof that we’re aware of, roof near the chimney was recently re felted.
The guttering is bad and needs replacing
If it helps it’s a semi detached and the neighbours recently removed the chimney breasts, could all the vibration damage our side? There was a lot of vibration!
Also, can the wall be saved?? We only painted at Christmas and can’t get this paper as was here when we moved in

Ken010 · Post by **Ken010** » Fri Oct 23, 2020 6:36 pm

Ont the images posted, I cannot see any staining.

You mention in your poet that the Vent above floor level has been blocked??

As a first step, can you re-open this vent? it has been placed there to prevent Condensation from forming inside the chimney flue, what happens is in an unused old flue which does not have the internal vent near the floor and a vented cap on the chimney pot is as stated Condensation, after that Chemical reactions occur between the old sulfate laden soot, once damp / wet the soot can and does form a weak Sulphuric Acid, this Acid in turn attacks lime mortar.

Is there a vented cap on the chimney pot?

Ken.

Jo2107 · Post by **Jo2107** » Sat Oct 24, 2020 1:57 pm

Hi, it’s the darker patches circled in red. The vent isn’t blocked, just has a sliding panel over the front to close it, which we have now re-opened.
The chimney has a metal caged cowl to stop birds getting in

Ken010 · Post by **Ken010** » Sat Oct 24, 2020 7:44 pm

The metal bird guard will not stop rain penetration into the flue.

As for the hit and miss vent on the wall?? Can you try a simple test, get a bit of thin tissue paper and hold it against the vent, if it is either blown away or drawn towards the vent then the vent is operating.

What does on occasion happen is that debris falling down the flue, builds up and blocks the room wall mounted vent?

Ken.

Jo2107 · Post by **Jo2107** » Sun Oct 25, 2020 1:48 pm

Hi, i was wrong about what’s up top, the chimney is split in 2, one part serving the living room which has the flue, the other serving the bedroom, which hasn’t had a fireplace in years.
I can hear airflow in the vent but the tissue is neither blown away or to the vent. Not sure what the top of the chimney looks like, but i guess the chimney won’t have been swept in many years, i guess first thing see if my chimney sweep can do it?
Attached photo of the top of the chimney, circled is the one connected to the bedroom, also a photo of the vent

wes56 · Post by **wes56** » Sun Oct 25, 2020 2:22 pm

Jo2107,
you show two different flue terminals:
1. the front clay mushroom is for venting redundant flues.
2. the rear one is, i think, a metal anti down draught cowl.
Flashing on stacks should be in lead not some possibly leaking fillet of mortar and a few tiles.
What condition is the stack flaunching in?

The chimney breast you show might need opening up for a chimney sweep to access the flue - you dont show the Hit and Miss vent?
To make good the plastered surface hack off the plaster and go back on with lime and sand render.
Do you have a picture of the bedroom chimney breast?
How many rooms in your house have chimney breasts?
If you go in the loft you will see how your chimney breasts are going up to the stack on the roof.

Jo2107 · Post by **Jo2107** » Sun Oct 25, 2020 3:10 pm

The clay one is the back of the house connected to the bedroom in question, a repointing firm think the chimney has been done but not very well and did mention the flaunching looks like it could do with replacing, which we will do.
The living room and bedroom above it have chimney breasts.
Attached photo of the bedroom inc the vent hole right at the bottom, I’ve taken some photos inside but unfortunately can’t see anything, though there is actually very little airflow .

wes56 · Post by **wes56** » Sun Oct 25, 2020 4:59 pm

So you have:
1. Lead flashing needed to replace present detail.
2. Flaunching inspected or re-done.
3. Stack to be repointed.
4. One or perhaps more flues to be swept?
5. Damp stained plaster to be renewed.

The log burner will work best and safest if it has a SS flue liner.
The neighbour's should have checked (PWA) if you had removed any chimney breast's before removing their chimney breast's.

Jo2107 · Post by **Jo2107** » Sun Oct 25, 2020 5:19 pm

Thanks Wes, i know this is a long shot but is there any way we can get away with not having to strip and replaster that upstairs chimney breast? We can’t get that wall paper as it’s old and we only repainted last Christmas

Typical for something like this to happen after we’d decorated! No issues the 5 years before hand.
We will get the chimney sorted with the repointing as a priority followed by new guttering

wes56 · Post by **wes56** » Sun Oct 25, 2020 8:37 pm

You could do the other work, and then wait and see but sweeping the flue and stopping any leaks are the most important issues for the plaster.
aamoi: you should examine the sides of the chimney breast and the return walls in the alcoves.
You've not said anything more about the loft chimney breast or posted a pic of it.
Whats the gutter you keep mentioning - the plastic guttering at your eaves has nothing to do with the stack?

Jo2107 · Post by **Jo2107** » Mon Oct 26, 2020 8:17 am

Apologies one picture is blurred! Included pictures taken inside the unused chimney, though as you can see despite me lightening the pictures it doesn’t show anything. There are no damp patches on the return walls or in the alcoves.
Also attached a picture of the downstairs chimney breast if it helps, that is connected to a flexible flue liner that is swept annually.