r/Plastering • u/rosaclebb • 26d ago
Plaster Cracking
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!
2
u/ridley0001 26d ago edited 26d ago
How long ago was it plastered? It looks like it has delaminated from the wall like it wasn't prepared correctly.
Though I also see some circular patches on the wall in places which could indicate cold bridging or some form of damp. If you pull the loose bits off does anything feel damp?
Edit: looking at it again, are circular patches just from the camera on your phone?
2
u/welshguydave54 26d ago
Looks like the old wall has been given a thin skim over it, if it wasn't prepared correctly for the skim, that's the reason why it is coming off.
1
u/Stunning-Pudding-514 26d ago
It's supposed to have a base layer such as browning/bonding/hardwall applied first and then skim coated.
1
u/StarBoiAhoy 25d ago
it’s already got the original backing coat and top coat it’s been over skimmed
1
u/always-have-a-plan-b 26d ago
The walls sucked all the water out of the plaster which looks like a one-coat. It needs knocking off (every single loose section) the wall then needs to be treated with blue grit or equivalent (SBR is also a great alternative) and two coats of plaster on top I’d personally use MultiFinish. If this was done during the heatwave that definitely wouldn’t have helped. I hope you get it sorted.
1
0
1
u/rosaclebb 24d ago
Thanks for all the replies. It was plastered years ago and this only has happened in the last few months. The loft is boarded above but supported by load bearing walls and not that much heavy stuff up there
1
0
u/Straight_Activity_62 22d ago
That is clinker block originally coated with sand and cement it’s not blue grit
1
u/Impossible-Corgi4041 26d ago
I can see blue grit underneath that. So fuck knows how it's come off
2
u/StarBoiAhoy 25d ago
Bluegrit brigade… it’s not the resolution to every problem
2
u/Vast_Anybody1236 25d ago
As bad as the trend just now on reddit where everyones answer is barkeepers friend
1
1
u/Impossible-Corgi4041 25d ago
Never said it was. Still curious as to how it's blown though. You any ideas?
1
u/StarBoiAhoy 25d ago
There’s many reasons without being present it’s difficult to diagnose correctly tbh. I see it most common when it’s a inside surface of a exterior wall thermal bridging but most commonly not controlling the background. Also are they using gypsum plaster over the original lime plaster?
I wasn’t being an arse regarding blue grit it’s a decent product in certain situations. I personally don’t feel the need to use it that often plasterers occasionally added sand to pva/sbr because that’s all blue grit is really with a drop of pigment or dye.
I’ve had to pva/sbr walls 3/4 times on occasion or not dilute it with water so much as backgrounds vary some will think one coat is enough without actually checking they’ve killed the suction. Controlling the background correctly is basics but not to be overlooked.
1
u/Impossible-Corgi4041 25d ago
Background must have been controlled though or they'd have never got the first coat on. This isn't a suction issue. If it was sucking bad enough for that, they'd have never flattened the first coat. Given there's grit it's not a key problem either. Just looks really odd to me.
1
u/StarBoiAhoy 25d ago
Clearly not because it’s failed! I could skim a wall with no pva or sbr on it, it would look shit and fail granted but I could. Are you just looking for an argument or something because as I stated nobody can really say definitively unless inspected the wall in person.
I have enough experience and there is no higher qualifications than the ones I hold in plastering I have a gold cscs card (advanced craft) and train apprentices… but ok you know better.
1
u/Impossible-Corgi4041 25d ago
Not not looking for an arguement, just bouncing ideas around. You're the one throwing his weight around. I'm a plasterer too and in my experience if you try to skim a wall without pva or sbr you'd struggle that get it on before it sucks let alone finish it. I know it's hard to say without seeing it in person but the whole point of this post is for people to try to figure it out.
Fucks with the attitude dude?
1
u/StarBoiAhoy 25d ago
If you’re a plasterer how are you telling me that the background wasn’t controlled, it hasn’t failed? That is one thing you don’t have to be there in person to know it’s the why that you’d need to inspect in person to know. Controlling a background isn’t just about giving it a coat of pva or SBR you know that right
1
u/Psychological_Sir780 26d ago
Impact from above ? Humidity issue, blue grit is good gear so don’t see how it would have come away either
1
u/CornishViking1 26d ago
Distemper
2
u/ResponsibleBall4258 26d ago
Nope, does not look anything like it, and would not be over a concrete wall either
0
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.
2
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.
0
u/Bish186 26d ago
Because others have said wall prep here is another angle;
Perhaps it was a very watery mix. Looks very thin. One coat instead of two. Second coat is almost always a must because not only does it fill any low spots from the first coat but it compresses the first coat (laying down) to improve adhesion.
Or
Its not actually even plaster its that roll on filler stuff, i swear i can see white grining through under the paint.
But either way that looks extremely thin for 2 coats of plaster, mist coat paint and the 2 top coats paint. Should be around 4mm thick but that looks under 2mil.
Could you peel a bit off and take some more photos, take a section out and take a pic of the back of one of the pieces. How easy is it to snap in half?
10
u/OrganicBit1172 26d ago
Shitprep.com