Blemish On Plastered Surface

[Brian1960]

Any idea what could be causing this on the plastered surface?
It's gradually appeared over time.
It's on a chimney breast wall which has no other issues.
What's the best remedy to sort it?
Thanks in advance.

 

[Harry Bloomfield]

Is the chimney in use, is there some through ventilation, if not?

 

[Brian1960]

Chimney breast has inset electric fire, cowl on pot

 

[Harry Bloomfield]

Chimney breast has inset electric fire, cowl on pot

Disused chimneys need a flow of air, in the bottom, out through the top, to keep them damp free. Is there a vent panel behind the electric fire?

Does the plaster in the area of your photo, sound hollow, when tapped?

 

[Brian1960]

Fire sits in open fireplace, plaster seems pretty sound around affected area, no other parts are affected.

 

[Harry Bloomfield]

Fire sits in open fireplace, plaster seems pretty sound around affected area, no other parts are affected.

Then, if it has definitely appeared gradually, it must have been blown out by damp.

Other than that, you have simply not noticed it before. Is the surface at all crumbly to the touch?

 

[Koolpc]

Salts coming out from the wall a possibility.

 

[Brian1960]

Would it be possible to chip out to brick, seal with SBR, fill with sand/cement mix, finish with filler?

 

[sparkwright]

Would be worth digging this out - if only to confirm that there is a brick present, and not a load of plaster or newspaper filling up an old hole.

 

[Brian1960]

Thanks all for your replies, much appreciated.