Why is this paint/plaster failing on INTERNAL walls?

WIAWSNB

Well, we can narrow this down - it's either coming from above, or from below. cough

If from below, ie 'rising' or burst/leaking pipe, then it's pretty severe. If from above, then it's presumably making its way down the cavity, before bottoming-out and then rising again.

Clear photos of that outside back wall would help, but you are essentially looking at anything suspicious around that upper window, the roof above, and where the extension joins the wall. If you take some clear photos, folk can zoom in and possibly make some suggestions.

Meanwhile, what I would do is hack off the plaster in these areas, especially in the extension - it's almost certainly going to need to come off anyway - and also that short length of skirting. Expose the brick/block/stone wall, and you should hopefully be able to more accurately ID the 'source' of the damp.

FrankFalcon

That conservatory was already there when we bought the house. We suspect that the tenant possibly never opened one of the small windows in that conservatory/Kitchen so next week we are having an external, electrical fan installed in the external wall of the Conservatory next to the door to the yard. Do you guys think that contributed to the problem. I should add too that the other walls in this 'conservatory' show evidence of damp on the emulsion, but they're not flaking etc.

WIAWSNB

https://forums.moneysavingexpert.com/discussion/comment/82037946#Comment_82037946

This is only my opinion, but these damp patches look to be too focussed, too severe, and too low for condensation. Also, it's on an internal wall.

I suspect rising or falling.

Albermarle

https://forums.moneysavingexpert.com/discussion/comment/82037858#Comment_82037858

If from above, then it's presumably making its way down the cavity,

From the photo it looks like a Victorian terrace, so will most likely be a solid wall.

Eldi_Dos

Can you see walls behind any fitted kitchen units, by removing drawers or plinth boards.This will help you to see if problem is only localised to the two places highlighted.