dump started recently show on the chimney breast

[Zehroni]

A sign of dump started recently show on the chimney breast as it enters the first floor bedroom, I install though the flushing leadwork needing sealing. My roofer went up to have a close look and he said that leadwork is in very good condition and he could not spot any gap or leak. I went into the loft and to my surprise the chimney stack is dry. My roofer does not know exactly what is causing dampness and he suggested that repointing the chimney stake may solve the problem.
Any idea please

 

[Zehroni]

Sorry I meant to say Damp and Dampness

 

[noseall]

Have a look at hygroscopic salts etc. Chimneys, in particular those that have bunt solid fuel etc are prone to hygroscopic saturation which reveals itself as brown staining.

Frustratingly, the staining only usually shows up once walls have been decorated.

Another cause can be sooted bricks bleeding through or a combination of the two. To rectify usually involves coating a chimney breast in S.B.R. combined with a coat of sand cement render with suitable additives.

 

[Zehroni]

Noseall, many thanks for the reply,

Can you please elaborate more on how it can be rectified?

“To rectify usually involves coating a chimney breast in S.B.R. combined with a coat of sand cement render with suitable additive”

Do you mean the chimney part inside the bedroom where the damp is showing or the outside part above the roof?

What does S.B.R mean? Is it type of sealant chemical?.

 

[Alastairreid]

The breast is coated in the affected room to stop the leeching from within the stack.

The idea is to strip back the plaster to the bare brick, apply a coat of SBR slurry (sbr with a couple of handfuls of cement) http://www.watco.co.uk/sbr-waterproof-additive.html

Then render with waterproof additive.

This will stop any chemicals which have accumulated within the stack from penetrating to the warm side of the vent,,the room.

Then you can plaster and paint.

 

[adamr7747]

Is the chimney in use?

 

[Architexeter]

If the chimney is not in use has the chimney got a ventilation cap?