About a year ago, we blocked up a fireplace with thermalite blocks. We then plastered over it (a coat of onecoat followed by a thin coat of multifinish).
The whole room was skimmed at the same time, and subsequently painted.
We didn't put an air brick in, because the chimney has been removed. This is a single fireplace stack, the chimney has been taken down to below roof tiles, and the fireplace blocked up.
All has been well up until now - I've just noticed that the paint (plain emulsion) is peeling in two patches, about 6"x6" each, just above the skirting, and just to the sides of where the blocked up opening is. The paint isn't peeling over the blocked up area, just at the two lower corners.
_________________ | | | old opening | | blocked up | peel | |peel ________| |___________
The room is kept nice and warm, and is reasonably well ventilated.
Any thoughts as to the cause and remedy? Condensation in the stack? If so, why in those two spots?
TIA