'Dead' plaster on the wall - paint over or what?

[ProfessorDent]

Hi, I apologise for my ignorance on this matter, I am just about to get the decorators in to look at this, but there seems to be a bubble in the wall here, from damp maybe? When you tap this part of the wall, it seems dead and hollow and as you can see, it doesn't look good?

Before I get someone in, should there be someone who can have a good look at the structure of the wall? It is obviously not a case of painting the wall, the whole thing looks kind of lumpen. Any thoughts, I'd be most grateful?

I had blown plaster in certain areas of my walls when we moved home, we stripped the blown bits back to brick and re plastered.
But I did this on the advise of someone who knew about it, could you get a plasterer in to have a look?

Probably water penetrating from outside. We had something similar in SW corner of our house and are having to have rendering sorted and then plaster sorted. You really need a professional to look at finding the source. A patch up will just become a mess again.