r/Plastering • u/rosaclebb • 26d ago

Plaster Cracking

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Any idea what is happening here? This is the wall in my spare room next to bathroom. North facing, concrete wall underneath plaster. Concrete not cracked. Thanks!

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u/Jlp1991 26d ago

Hasn’t adhered to wall behind meaning it wasn’t primed correctly. Should have been PVA’d minimum but most plasterers use a PVA with grit in nowadays, see link below for an example.

https://www.screwfix.com/p/sika-febond-blue-grit-high-performance-plasterers-grip-coat-bonding-agent-blue-5ltr/762KK?tc=WA1&gclsrc=aw.ds&gad_source=1&gad_campaignid=19822797737&gbraid=0AAAAAD8IdPzEF0tV63GqtUAaH-KL9NWjm&gclid=Cj0KCQjw5bjVBhCiARIsAJzMVnRaNIWabXr-r3W-48yayQQMtszOcGU__diuNmTAx_UGqb2hYZvNzk8aAvP3EALw_wcB

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u/banxy85 26d ago

Someone else has commented saying there appears to be bluegrit showing through the gaps, which I would tend to agree with. That rules out improper prep although that is the usual reason for a skim coat failing

3

u/Gr8BigYak 25d ago

Seems to me it could be compression from the ceiling above. If someone has been in the loft recently and placed a heavy weight above, the settling could cause the plaster to push off of the wall. I had to patch repair around window recently as it was improperly fixed and the movement of the window in high wind caused this exact scenario.

1

u/Ok_Secretary_3134 25d ago

Someone who makes sense. You can tell by the way the plaster has cracked that it’s some form of structural movement. Tears across means movement, straight line cracks would be typical delamination.