Peeling Paint, Discoloured Plaster - Advice Needed

[HandSlander]

I've had patches of peeling paint near my skirting boards in my extension. Having scraped off the loose paint, the plaster underneath is discoloured. It is not obviously wet to the touch, but appears like some moisture may be getting through.

The photo is taken from the ground floor extension to the original 3-storey Victorian brick, and this wall is the original thick brick cavity wall for the property (outer leaf visible). It may be that some dampness and detritus has built-up inside the cavity over a century, so will be almost impossible to fix. There is no plumbing in this area, nor leak from the ceiling etc.

Should I just paint over with Zinsser BIN which I have to hand to see if it holds?

 

[Sunshine32]

Yeah sure you can put BIN on it or Cover Stain but it’s not going to get rid of the damp for very long. The moisture is just going to push the paint off again at some point, plus your plaster has no doubt blown by now. I would investigate the water problem further. What’s happening with your roof? Is it all intact or is it in-fact responsible for this? It looks like you may have had a leak for a long time and the water is now leaching it’s way back up the wall but only you will know as you know how your house is structured.