Bonding coat bulging.

#1
Hi, hope someone can help. About 2 years ago I plastered the kitchen. I have recently noticed some wall tiles cracking so I removed them to find the bonding coat bulging. I have never seen anything like it before. It was perfect when applied and then skimmed. It’s has three bulges/ lumps about 4 inches in diameter and sticking out about half an inch, and hollow behind. Has anyone seen this before and what could have caused it?
 

norman moss

Well-Known Member
#4
the fault lies with the prep/ going over a greasy background or silk emulsion etc can cause it.
 

Havagojo

Active Member
#7
Check wall outside
If it had been OK after skim would have thought only damp would cause bulging , water from above down behind tiles , or as you say outside , no cavity or snots catching condensation (or leak )/from window above
 
#8
Thanks for your replies. I don’t think it’s lack of pva as there is no cracking to the bonding coat just lumps appearing pushing tiles off. Damp makes sense though as it’s under an old brick flue and the extractor fan is cored out just above. I’ll get on the roof and check the top of the flue.
 

Havagojo

Active Member
#9
Thanks for your replies. I don’t think it’s lack of pva as there is no cracking to the bonding coat just lumps appearing pushing tiles off. Damp makes sense though as it’s under an old brick flue and the extractor fan is cored out just above. I’ll get on the roof and check the top of the flue.
If its cavity wall without insulation around hot pipe could condensate and get water seeping by chance ,be surprised if that's enough to cause your outcome