Damp spot on plaster behind wallpaper - plasterer coming next week.

[cherryblossom123]

Hi, I'm currently removing the wallpaper from my room as I've got the plasterer coming next week to overboard and skim.

I noticed in one spot and a bit around it when pulling the wallpaper off it was sticky and tacky and the plaster was a darker colour as you can see.

I was a bit concerned and curious so I (not sure if it was stupid or not) I hacked a bit at it, surprisingly enough the layer underneath (not sure if this is more plaster or another material was not sticky or tacky or wet it looked like this underneath partly it went to brick in one area

I just wanted to check a bit more so I hacked a bit more off and then I noticed there was something? I think it could be a brick with mould on it? Or maybe it is something else.

I didn't mess with the wall anymore, but I'm a bit worried as to what is going on here, if it is indeed mould then why is the adjacent brick looking completely fine despite it being right underneath the wet patch?

The room is a back living room of a 1930s semi detached house. It's a flat wall and is a party wall so I don't know where it could be coming from, I'm guessing on the other side it is the neighbours' kitchen or possibly living room I'm not sure, but there is no gutter or anything. In the bedroom room directly above there is 2 alcoves so possibly a fireplace upstairs in the past but there isn't an alcove in the room I'm talking about so really not sure. Here is the view from the garden the wall I'm talking about is the one at the bottom left of the photo (the one with the French doors)

Can anyone please tell me what is going on, and if it is anything to worry about? Also do I need to do anything before the plasterer arrives next week? Or when it comes to eventually painting this room?

Thank you!

 

[ree]

OP,
When did you first notice staining on the party wall?
A long shot but maybe a chimney breast was removed, and the black stuff you expose was the back wall of the old flue. The black stuff being the soot residue of historic solid fuel fires?
The top brick courses of the chimney stack are contaminated with penetrating soot.
A pic of the wall showing floor to ceiling might help?
Why are you going to use plasterboards?
Presuming that you have a suspended floor but on the outside pic its difficult to see if you have air bricks?

 

[opps]

If the chimney breast has indeed been removed, the black could be old soot.

Google hygroscopic salts. They can soak up moisture and release it later, that said it is normally over winter rather the summer.

One of my customers had it and, at the time, he was advised to use sand and cement. I have seen other people say that fixing plasterboard with PU foam adhesive is sufficient.

Does your neighbour still have their chimney breast? If not, it cannot be down to hygroscopic salts.

 

[Scally-Ho]

My thoughts immediately turned to the remaining part of the chimney and what is in place holding it up?

 

[cherryblossom123]

OP,
When did you first notice staining on the party wall?
A long shot but maybe a chimney breast was removed, and the black stuff you expose was the back wall of the old flue. The black stuff being the soot residue of historic solid fuel fires?
The top brick courses of the chimney stack are contaminated with penetrating soot.
A pic of the wall showing floor to ceiling might help?
Why are you going to use plasterboards?
Presuming that you have a suspended floor but on the outside pic its difficult to see if you have air bricks?

I only just noticed it today as nothing was coming through the wallpaper. It could be possible soot based on the position of the alcoves in the above bedroom, I'd need to check. I can send over some photos later. Plasterboards are just for the ceiling I'd assume the plaster will just skim over this wall directly without boards.

There are too air vents sat just below the floor level, they are not visible in the picture (blocked by plants)

 

[cherryblossom123]

If the chimney breast has indeed been removed, the black could be old soot.

Google hygroscopic salts. They can soak up moisture and release it later, that said it is normally over winter rather the summer.

One of my customers had it and, at the time, he was advised to use sand and cement. I have seen other people say that fixing plasterboard with PU foam adhesive is sufficient.

Does your neighbour still have their chimney breast? If not, it cannot be down to hygroscopic salts.

It could be soot I guess maybe they removed the downstairs part but didn't do it upstairs (as that still has alcove) there is still both chimney breasts but I thought they were for the front room which definitely had a flue . It's possible it just stayed damp from before? I don't know why it didn't make the prior layer of plaster damp though hmmm

No idea about the neighbours, if it is soot what would you suggest I do?

 

[cherryblossom123]

My thoughts immediately turned to the remaining part of the chimney and what is in place holding it up?

No idea but I'm not aware of any works in the last 30 years (I just bought the house recently) and it had a level 3 survey which didn't highlight anything on that front? Possibly there was never a fireplace upstairs but just the flue from the downstairs going up? Then it wouldn't be too heavy maybe?

 

[ree]

OP,
Hygroscopic chemicals can appear on the decorated surface at any time of the year.

Sand & cement or plasterboard are not sufficient & could cause further problems - the correct remedy is to hack off all the contaminated plaster back to brickwork & then render with a 3:1 sand & NH lime render mix.
Skim finish with, say, Limelite finish. Dont use any gypsum plaster.

If your neighbour still has his shared chimney breast, & if its redundant it could actually be passing Hygroscopic chemicals through the party wall to appear on your side.
However the neighbour's could have an active fireplace & warm flue - or the party wall might be a cavity wall?

Why not post a pic of the bedroom chimney breast? Are there any other chimney breasts in the house?

 

[cherryblossom123]

OP,
Hygroscopic chemicals can appear on the decorated surface at any time of the year.

Sand & cement or plasterboard are not sufficient & could cause further problems - the correct remedy is to hack off all the contaminated plaster back to brickwork & then render with a 3:1 sand & NH lime render mix.
Skim finish with, say, Limelite finish. Dont use any gypsum plaster.

If your neighbour still has his shared chimney breast, & if its redundant it could actually be passing Hygroscopic chemicals through the party wall to appear on your side.
However the neighbour's could have an active fireplace & warm flue - or the party wall might be a cavity wall?

Why not post a pic of the bedroom chimney breast? Are there any other chimney breasts in the house?

Thanks for the information will mention it to the plasterer. I can post photos later. There is a chimney breast on the front side of the house too, there used to be a fire in the front living room, it has been boarded over and plastered, capped at the top with a vent in the living room for air circulation.

 

[cherryblossom123]

OP,
Hygroscopic chemicals can appear on the decorated surface at any time of the year.

Sand & cement or plasterboard are not sufficient & could cause further problems - the correct remedy is to hack off all the contaminated plaster back to brickwork & then render with a 3:1 sand & NH lime render mix.
Skim finish with, say, Limelite finish. Dont use any gypsum plaster.

If your neighbour still has his shared chimney breast, & if its redundant it could actually be passing Hygroscopic chemicals through the party wall to appear on your side.
However the neighbour's could have an active fireplace & warm flue - or the party wall might be a cavity wall?

Why not post a pic of the bedroom chimney breast? Are there any other chimney breasts in the house?

Hi here are the pictures, I scratched a bit of the black brick and it definitely smells like soot! So I think you must be right.

Here is the picture of the full wall

Here is the upstairs wall in the room directly above

Not sure why the alcoves would be needed there and not downstairs, maybe they removed the old fire but never changed the upstairs.

Then here is the equivalent top and bottom rooms at the front of the house

Downstairs ( I had the chimney capped and the the hole boarded

Upstairs

Can you let me know what you think I should do next please. Thanks!!!

 

[ree]

OP,
Thanks for the new pics.
1. Where the rear downstairs c/breast has been removed then do as I suggested above in post #8.
2.The rear bedroom c/breast contains two flues - both flues need venting: a centred vent might catch both flues if a feather brick can be dislodged?
3. Given the state of the external chimney stack soot penetration (pic #4) then both flues are probably unswept & therefore Hygroscopic defects appearing on the chimney breast is a future possibility? But venting should help.
4. At some later time, pics of the rear & front chimney stack flaunching - pointing - & flashing could be posted on here?
In the meantime, go into the loft & examine the rear & front c/breasts. Look for soot or water stains.

5. The front downstairs c/breast looks fine but was the flue swept?
6. The upstairs c/breast is not vented - & presumably not swept?
7. The bedroom c/breast contains two flues.

 

[cherryblossom123]

OP,
Thanks for the new pics.
1. Where the rear downstairs c/breast has been removed then do as I suggested above in post #8.
2.The rear bedroom c/breast contains two flues - both flues need venting: a centred vent might catch both flues if a feather brick can be dislodged?
3. Given the state of the external chimney stack soot penetration (pic #4) then both flues are probably unswept & therefore Hygroscopic defects appearing on the chimney breast is a future possibility? But venting should help.
4. At some later time, pics of the rear & front chimney stack flaunching - pointing - & flashing could be posted on here?
In the meantime, go into the loft & examine the rear & front c/breasts. Look for soot or water stains.

5. The front downstairs c/breast looks fine but was the flue swept?
6. The upstairs c/breast is not vented - & presumably not swept?
7. The bedroom c/breast contains two flues.

Thank you very much for the reply, let me address those points please.

1. Thank you will ask the plasterer.

2. Possibly, I've fully decorated that one now and when I was stripping the paper I didn't notice any damp patches etc. I know you mentioned it can appear at anytime, I may just hope nothing appears and leave it and see. I can't spend more money on getting vents added, plus it would be difficult to do when the room is refurbished?

3. Yes they are unswept as far as I am aware. I suppose it is a possibility, will leave that for now and hope it won't appear. I had a bent put in the front room at least so hopefully less chance.

4. The chimneys have been looked at a few weeks back, just externally, they were capped and they did some external work (pointing, flashing, etc? I don't know the specifics but a guy was up there and sorted what needed looking at as far as I am aware?!

5,6,7. Nothing swept as far as I am aware, so it is possible soot has been there for a while and could activate in future. Having said that I'm not aware of the previous owner removing any fires etc. I'd assume it must have been several years and possible prior to their ownership (1990s or so) so it may be that it was swept when it was taken out, in the front?

Basically the front room doesn't seem to have caused any issues for several years so could well be okay going forward.

So the 2 take aways for me are that I need ti get the plasterer to look at that damp spot. I will do this.

The second one is that ideally a vent would be added in the room directly above, ? Is that correct? I don't want to do this since it has been decorated and a new carpet has gone in? Could I add a vent near where the damp spot is in the downstairs room? Basically similar to what I did in the front room? Not sure.

If I didn't vent but got the plasterer to look at it do you think that could be sufficient? I could even use a damp primer like zinzner sell? Not ideal but maybe not too bad.

Would welcome your thoughts.

Thank you so much again.

 

[ree]

OP,
Installing a vent is a simple, 30 min job.
Roofers should provide pics or video of their work on stacks?
Definitely dont start venting the damp spot on the party wall.
I've already told you twice what to do - forget Zinger and similar.

 

[cherryblossom123]

OP,
Installing a vent is a simple, 30 min job.
Roofers should provide pics or video of their work on stacks?
Definitely dont start venting the damp spot on the party wall.
I've already told you twice what to do - forget Zinger and similar.

Okay, roofers never provided anything, they were hired by the main company doing the job and have been working with them, I didn't hire them directly, they weren't here too long maybe 1-2 hours.

So where does the vent need to go, in room directly above the damp spot? Or in the other bedroom (the one that is directly above the one with the vent already?

 

[cherryblossom123]

Okay will do! I just need to use the suggested plaster mix right?

Also where should I put the vent? In the bedroom directly above where the damp is? Whereabouts? Cheers!!