New plaster coming away from wall

21 Mar 2016
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United Kingdom
Ive had a plasterer in 6 weeks ago to render and multi finish the walls in my house.
I had rising damp so he removed a meter of old plaster and render back to the brick. I injected the walls with dryzone cream.

The plasterer put on 1 coats of render with renderguard gold waterproofer added into the mix and another coat of render on top without waterproofer then skimmed with multi finish.

All seemed well until yesterday i noticed patches of plaster is coming away from one wall and sound hollow when you tap on it, if you push on the plaster with your hand it crumbles and breaks. Its like its not bonded to the render.
He pva the wall where the old plaster meets the new plaster.
The only thing i noticed was that he didnt scratch any of the render as ive seen others plasterer do it in the past, i did questioned him about scratching the render and he told me it will be fine and wouldn't be a problem. He also didnt scratch the first coat of render either but the render feels solid and doesn't sound hollow, its just the plaster coming away from the render. The other walls wasnt scratched too and seem fine so far.
Total area thats loose is around 1 square meter

There isnt sign of any damp now and seems dry.

Can anyone help and is the reason the plaster is coming away because he didn't scratch the render. The render feels smooth behind the bit of plaster thats falling off. What can be done now to correct it as the render its dry to scratch?
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He should of put a scratch coat on.left it a few days to firm up then a float coat on,devilled with a plastic float with nails or pins tapped into the top of his float then left it for a while then skimmed it . The idea of scratching and devilling is to give a "key" for the coats to adhere to each other. Sounds like a "Chancer" to me...Good plasterers know when to put each coat on so they stay on !!
I wont be using him again once its sorted he's already had all the money, i did at first held back £200 for 3 weeks to see if the plasters blows off the wall and it didn't so i paid him the full amount.

How can we rectify it now? Should be scraping all the blown/loose bits of the multi finish and making a key do it?
I was thinking thinking of chipping or angle grind load of lines on the render in the areas where the plaster has been removed/scraped off and pva 2 coats and get him to skim it again would that work to make a key?

As i said the render has bonded really well to the brick its just the plaster falling off due to i suppose the render being smooth and no key.
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What mix ratio should i tell him to do 3 part water 1 part pva?
I can't tell another spread what he should be doing! But if its porous its best to use a weak mix first of 5/1 and then a tacky layer of 3/1 if there's not much suction you could do 3/1 mix if there's no suction you could use stronger ect ect , why not take some pics and show us before and after pics?
Hi ive taken photos of 1 bit where its coming away. It was hollow and i pushed my finger in and it cracked see pics. Also you can juat about see the smooth render behind.
That's a horrible job you have there, there are hundreds of blemishes also its not taken to the wall the light switch is buried as well I recommend scraping it all off and getting it reskimmed I wouldent get this cowboy back to try and sort it his work is terrible
I know one thing for sure i wont be calling him back even to do any more work for me. I will let him have another go at it as ive paid for it already and shouldn't have to pay again for his cock up.
This house will be rented ive just accepted the finish he told me to sand the trowel marks and blemish. I know i shouldn't have to sand it but hes rubbish at plastering and i made the worst mistake by giving him all the money.

So do you mean scraping all the areas where there is loose/hollow multi finish or the whole lot including render. The render feels solid behind.
So to rectify it pva it let it go sticky/tacky and skim it?
Thanks for your help much appreciated.
What an awful mess. Steve and Roy have said all there is to say about this, but that is a shocking job. Even the edge of the door-frame is covered in cement, and the light switch,, well, that says it all. Was the chancer that did this mess self employed or was it someone you knew?
Take all the skim coat off as Steve says, and then check out the cement render underneath. Make sure it's not hollow sounding,, tap it all over. Also make sure it's not "SANDY/POWDERY. Try scraping your fingernail into the render. You'll soon know if it is sandy etc. Better still, get a an opinion from a reputable local plasterer, builder, someone who knows what they're looking at. Any un-certainty, take the lot off back to brick and start again. Shame on the chancer that ruined your job.
I mean to take all the skim off and reskim leave the render alone unless its uneven tbh if you get him to try and make good he won't be able to do it not with those skills , it looks like the skim won't take much to shift it
He was self employed and apparently doing it for 30 years hence why i gave him the job. I think he's a bricky rather than a plasterer but wants to be "jack of all trade"
Ok so ive found another plasterer and hes ready to start tomorrow.

He said he will remove the old plaster and render so now i will keep my eye on his work so from my understanding he needs to put on first coat of render to the brick wall using waterproofer (renderguard gold) and when it starts to set he needs to scratch the first coat and then apply second coat without waterproofer and scratch that too.

So when does he need need to apply the multi finish? Same day as the render? or does he need to let the render dry for a day?

Also does the brick wall need pva before he renders and also does the new second coat of render need to be pva before he plaster?

Thanks for your help i need to make sure its done right as im paying twice for a job that should have been done right in the first place.

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