Please help me with my plastering nightmare!

[Carey77]

We live in a mid-terrace built in the early 1900s. It has had a damp proof course treatment and this appears to be working effectively. Our problem is in the upstairs bedroom and the front room.
• Upstairs there is a brown stain that that runs vertically down the wall.
• Downstairs in one section of the living room wall (vertically) the plaster has bubbled and if you wipe the wall a powder residue comes off on your fingers. This is only 1.5 meter section width over the whole wall 5 meters.
Both sections of the wall (upstairs and downstairs) are along next doors chimney breast. Our house does not have a breast remaining. Next door no longer use a coal fire, but instead have an electric one in place. They don’t appear to have any problems on their side but its wall papered so not sure if this hides a multitude of sins?!
The chimney stack was removed last summer, and the roof retiled and sealed. We left it 6 months took the plaster off to the brickwork and then re-plastered and painted. However a year on we’re back in the same nightmare.
Someone has suggested that this could be next doors salts coming through. However this doesn’t explain upstairs to me.
I’m sick of throwing good money, time and effort at this wall please could someone advice as to what we should do.
• What do you think it is
• How to resolve it
Whilst it’s tempting to wall paper it I’ve a feeling the brown stain would penetrate anyhow.
Thanks in advance

 

[1john]

Was sand and cesment used on the bare brick before skimming? If so was a waterproofer used in the mix? Have you been in the loft to investigate?

 

[Carey77]

Yes sand/cement & waterproofing was used prior to the plastering.

My husband has been in the loft and can't see anything at all. All the roof seems to be well sealed and the wall all dry.

 

[NickB_99]

We live in a mid-terrace built in the early 1900s. It has had a damp proof course treatment and this appears to be working effectively. Our problem is in the upstairs bedroom and the front room.
• Upstairs there is a brown stain that that runs vertically down the wall.
• Downstairs in one section of the living room wall (vertically) the plaster has bubbled and if you wipe the wall a powder residue comes off on your fingers. This is only 1.5 meter section width over the whole wall 5 meters.
Both sections of the wall (upstairs and downstairs) are along next doors chimney breast. Our house does not have a breast remaining. Next door no longer use a coal fire, but instead have an electric one in place. They don’t appear to have any problems on their side but its wall papered so not sure if this hides a multitude of sins?!
The chimney stack was removed last summer, and the roof retiled and sealed. We left it 6 months took the plaster off to the brickwork and then re-plastered and painted. However a year on we’re back in the same nightmare.
Someone has suggested that this could be next doors salts coming through. However this doesn’t explain upstairs to me.

Whilst it’s tempting to wall paper it I’ve a feeling the brown stain would penetrate anyhow.
Thanks in advance

Some pics may help diagnosis.

Salts can affect the finish of a gypsum plaster applied straight onto the brick - but as you've got sand/cement/waterproofer under the skim, not sure how it could be this.

I would resist the temptation to cover with paper - you need to get to the bottom of it.

Only other suggestions -
If the roof looks good on your side - is it ok with the neighbours? Water can work its way along sometimes.
Is the remaining chimney covered with a decent cap? (still open letting air circulate, but a covered top not letting some water run down)

Any plumbing in that area - I've had this once before where I thought a flat roof was leaking and turned out to be from the bathroom.

I'm sorry I can't be more help than this.

 

[Carey77]

Thanks for the response. I will see what I can do on the picture front.

 

[joe-90]

A stain block will often work. The problem is caused by moist air from next door venting up the chimney and condensing. It's very common. If that doesn't work you'll have to take it back to the brick and use an SBR slurry then re-render with strong SBR render.