Cracks appear in skimmed plaster on lime plaster

[Trewheel]

my hall, stairs, landing and dining room were recently plastered. PVA was applied onto lime plaster and the walls were skimmed and then painted and several months later fine hair line cracks have appeared all over? Why might that happen? should i call the plasterer back? should he make it right?

 

[Micilin]

Were the walls sealed up 24hrs before skimming.?
Pva same day onto lime render is not the way IMHO and I would not use pva And skim
Onto trad lime render anyway.
Is it lime sand render or lime sand cement?

 

[Trewheel]

not sure about what type of lime plaster. how do you tell the difference? it is kinda yellow/ornge in colour, has small fine hair in it and can be sandy to touch. to my recollection, the walls were PVA'd left for a bit and skimmed the same day. cheers for your feedback so far.

 

[joe-90]

Houses move, just fill them and repaint.

 

[Micilin]

If they are irregular cracks like a mosaic, then I think the cause is skimming on to one application of fresh PVA where the wall had not been sealed properly. this is different to movement cracks. Obvious caveat -without seeing it.

If you rub your fingernail along them do you get a change in sound ? This indicates that areas are blown.

The problem is the plaster can be apparently finished perfectly on the day but the substrate is not sealed properly and sucks the moisture out of the skim so that it does not set properly. (In extreme cases it leads to 'turtling' where the pattern resembles a turtle shell with some edges curling up)

Often these cracks are not apparent until the plaster gets wet eg with paint.

Are they a pattern that is smooth on the surface, or actually cracks of 1mm +?

If the plaster is sound then you can fill and sand.

I would say it is the plasterers obligation as you agreed to have a reasonable finish and he did not prepare properly. If it is just a few mionor ones, fill, sand yourself as some minor cracking is acceptable

 

[Trewheel]

thanks for that. the cracks are less than 1mm. they are random and all over the different walls. i have been told that PVA is the wrong application for lime plaster, apparently its something called bond it. not sure where i stand legally, i am just threaders as its all walls and i don't wanna polly fill and paint, as the to get a good finish i would have to paint the all the rooms again. should the plasterer pay for my paint?

 

[joe-90]

You paid a plasterer to skim your walls. If your walls decide to crack then that's not his fault. Why do you think it is? My walls are skimmed lime plaster - never had a problem.

 

[Micilin]

If you ring up gypsum they will say you should use their product to seal and key their finish. So if you as a last resort(And I would not advise if possible ) went down the legal route the question would be did he apply as per maufacturers recommendations? Answer - No.

Someone here will chip in with legalese from Consumer legislation, but try and work a compromise as he may have skimmed walls like this before with no problems and assumed the conditions were the same, I don't think it was deliberate, just ignorance or inexperience

Some might might run their business in that way ie I'm finished, what happens next is your problem, , and good luck to them - but if for example I plastered over a crack that ran down the middle of the wall without remedying it or advising that it might open again, then I am not doing the job correctly.

Talk to the man, see what he will do, it may be that he has some integrity and will make som,e effort to help a solution,

The cracks are not shrinkage or settlement, both of which you should make a client aware of before starting, but down to incorrect preparation.

 

[joe-90]

It was OK for several months so hardly a prep problem. The house is most likely subject to thermal movement after a long cold winter. Tell us Micilin - just what would you have done that you would guaranteed indefinitely against thermal movement?

 

[Micilin]

It was OK for several months so hardly a prep problem. The house is most likely subject to thermal movement after a long cold winter. Tell us Micilin - just what would you have done that you would guaranteed indefinitely against thermal movement?

To pick out the detail from above posts for you:

1- Using plaster and bonding agent as per manufacturers spec

Legally , this ensures that anything that happens outside of your application is not your liability. A phone call to BG will tell the client that BG do not reccomend PVA to bond or seal

Practically, Bondit will allow some hairline cracking behind it unlike PVA.

I would also have brushed water over the old plaster to see if there was any cracking before application. there is often cracking in the backing coat that is not easily visible when dry. You can get the same with painted external render that only shows up after rain.

I honestly don't know about the usefulness of indefinite guarantees against anything.

I've not seen the job before and after, so will have to agree to differ on what is 'most likely ' but the above can be lesson for those who like to learn.

before Bondit i would have used SBR the day befor to seal, then plastered onto a tacky second coat of SBR after 24 hours.

PVA and Plaster same day doesn't seal up effecitively

 

[joe-90]

SBR won't stop thermal movement. So he'd sue you then.

It's also well-known that lime rendered walls need to 'breathe'. Is Bond-it a breathable compound?

 

[Micilin]

SBR won't stop thermal movement. So he'd sue you then.

It's also well-known that lime rendered walls need to 'breathe'. Is Bond-it a breathable compound?

If the cracks showed I would try and put it right, and If I didn't he would have every right to sue me and would win as I went off spec.

However, IMO the SBR would seal it well enough, and be flexible enough behind the skim to stop the cracking, which is why I would have used it pre Bond it.

If I used Bondit, it would be per BG spec so I would be fine . Again I do not think it would crack due to the nature of the product. But if it did I would be confident that I was not liable , although I would make a good effort at sorting out the problem as word of mouth and reputation are how I get work, rather than washing my hands of it.

Remember you are assuming that is is thermal movement and not related to prep. I maintain that the prep was wrong and hence plasterer needs to compromise. There is no way you can say the appllication was correct whereas I can definitively say it was incorrect.

And joe, you really do tell some good ones - "It's also well-known that lime rendered walls need to 'breathe'" after all you have posted here about that !!!

Excellent, made my evening!

OP- Talk to the spread and see how reasonable he is

 

[joe-90]

It's his wall and he asked you to skim it - not your problem if his wall shrinks. Bad prep shows up in days - not months later. You have now sealed his house making it non-breathable, and thus very prone to condensation issues. Well done.

 

[Micilin]

Don't get it joe - you are saying that you are familiar with this 'thermal movement', in lime render and know it is a likely issue in this scenario; but you would still plaster the walls as the OP's plasterer did and walk away from it without discussing with with the client or looking for an alternative prior to agreeing to do the work .

When the cracking occurs then you would say 'not my problem guv, they are your walls'

Bad prep does not always show up in days joe - you should know that!

(And If there is condensation in the room, how do we sort rooms with non breathable materials? I'm surprised at your stance on this one !)


OP - Apologies for going off on a tangent but you can see there is a different attitude to customer service among the users here!

 

[joe-90]

The OP simply has to repaint it. The thermal movement of his central heating cycle has caused the cracking and that's not the plasterer's fault.

The only way to beat this situation is to add PVA to the plaster as an admix - as it will then move with the walls rather than crack. SBR won't stop the skim coat from cracking - the only way is to add elasticity to the skim.

I just get fed up of people looking for people to blame, who can I sue, what can I get for free. FFS it's only a few hairline cracks.