Replastered ceiling - quality of work

[KevinH]

We have recently had a lath and plaster ceiling replastered (with lime plaster) because the plaster had debonded. The plasterer thought that the laths were in good enough condition to not need replacing, although he said he couldn't guarantee that they would hold. The ceiling looked good when he had finished. He also told us that there would be some shrinkage cracking. 3 months down the line, there are more cracks than we expected, some 2-3mm across and in places the ceiling now has a 'step' in it across some of the cracks with one side being 3 or 4mm higher than the other. Before we ask him to return to offer his opinion, what should we expect? Is this common for lath and plaster ceilings, or should we expect him to correct it? If so, what would be a reasonable expectation from such work?

Many thanks - guidance very welcome from anyone who can offer us an insight into what we should expect or from their knowledge and experience.

 

[Lime]

Obviously without seeing the laths before the plaster was put up this will only be a guess.
However it is not the laths that fail normally (unless they are rotten) it is the nails that hold them up on the joists.
From your description if sounds as if the plaster has cracked (perfectly normal) but the weight of the plaster has pulled a lath or laths away from the joist above.
Also, in some particular circumstances, a lath may bow out of shape caused by the water held in the plaster which may create a similar effect on the ceiling.
However the big difference will be is that the bowed lath will resist pressure to push back the plaster (so that it is flat again) but the lose lath will push back into place.
If the ceiling will push back into place (flat) then the laths above need further support.
I suggest screws rather than nails.
the difficulty may be to find the joists where they attach to the laths.

What the plasterer should have done is nail the laths up tight in the first place.

Also it depends on the plaster used.
The correct method should be to use a lime and sand mix.
This should be applied in the form of 3 coats... that normally takes weeks for each layer to set.

 

[Gervase]

Yup, it sounds like the laths have failed. It certainly sounds like more than shrinkage cracking, which should be irregular but not stepped.
Much depends on the original agreement. If you discussed the condition of the laths and he made the assurance, without any haggling between you over which would be the cheaper option or how best to consolidate the existing laths, then he ought to offer to redo the work. To be honest, it's pointless plastering a ceiling unless you have total confidence in the laths, which can be achieved using screws and washers or by fitting new laths. Putting the problem right for the second time is always going to work out more expensive in the long run, and the cost really should be borne by the plasterer rather than by you if no agreement was made on 'taking the cheaper option' following discussion about consolidating the existing laths.
Did he use plenty of hair in the plaster? For lath ceilings hair is absolutely essential to minimise cracking and give strength. Skimping on the hair will inevitably lead to more cracking and less strength.

 

[kevmiles1]

It is easy to see on a lathe and plaster ceiling which if any need replacing, then he should have used a haired lime plaster as a base coat and then an unhaired lime as a top coat and it should last for years if done correctly

 

[KevinH]

Many thanks for the replies and advice.

We did discuss the condition of the laths, and he did say that we'd get a longer lasting job if they were replaced, but he also said he thought their condition and that of the nails, looked fine. However he offered no guarantee about their condition. We took the old plaster down and the laths seemed sound to us. One or two were loose/broken and these were replaced by the plasterer. He used some hair in the first coat although we have no idea about whether it was an adequate amount - that should be his expertise not ours. He put a second coat on several weeks later, and then a finishing coat a few days after that.

The room is all redecorated etc. now with new carpet etc so this could be a difficult matter to resolve. I'll contact him to come and take a look and offer his opinion. Hopefully he'll be quite reasonable in his response and we can find a way forward. He did say he offered a 'Marks and Spencer' service (at a 'Marks and Spencer' price), so he'll have the chance to live up to that claim.

 

[Lime]

It would be advantageous if you could access the ceiling from above.. raise a floorboard.. to see if the lath has come adrift or whether the plaster has broken away from the lath.
If the latter it would be entirely the plasterer's problem.
Another argument used against you may be that the plaster has been dried out too quickly causing the cracking and break away.

 

[skier-hughes]

However he offered no guarantee about their condition.

This could be your stumbling block. Lets hope he comes and is amenable.

 

[KevinH]

Just to provide an update if anyone comes across this type of thing again.

I eventually managed to call the office when the chief chap was in the office. He arranged for his plasterer to revisit, and has repaired the ceiling. He said he'd never seen this happen before and was very apologetic. He believes that the laths warped/bent with the weight and in places pulled away where the plaster had cracked, and has screwed and filled the ceiling. He agreed that the old laths and nails had looked good and seemed sound enough when he worked on them, so wasn't certain what the cause of the problem was. It now looks acceptable, although not as good as when the work was first done, it doesn't appear to be cracking or moving now, but is a bit more uneven than ideal. We just need to view this as accelerating the character I guess.

 

[skier-hughes]

We just need to view this as accelerating the character I guess.

How philisophical