Finishing plaster not bonded to wall very well.

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Iotrez

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Hi all,

I put a mix of pva/water onto the wall before skimming with finishing plaster.

But now that the plaster is dry I've noticed that quite a lot of it is not bonded to the underlying wall very well.

A few small patches came off when I tried to paint, but now I find that I can put my knife under the plaster and it fairly easily comes off.

So my question is, how well bonded to the underlying wall should the finishing plaster be? Should it be stuck fast? Or should it be fairly easy to start taking it off with a knife?

I think I'm going to try again and this time do something someone on here suggested which is, seal the wall with 1part pva/5parts water. Let that dry and then put on another coat of 1 part pva/3 parts water and start to plaster when this layer is still tacky.

Cheers.
 
What did you pva onto ? Paint or plaster, was the wall dust free and oil/grease free.? Was the paint sound,or did it soak the pva straight in,?
 
I put the PVA on the painted wall before plastering.

After looking at the wall again, I'm starting to wonder if the problem was the the old layer of finishing plaster was not well bonded to the wall and that my new layer just come off with that.

maybe I should have tried to take off the original layer of finishing plaster?

Do you normally skim straight over an old layer of skim, or should you try to get back to the undercoat of plaster first?

Thanks.
 
remember the substrate..ie. the paint has to be soundly bonded to the original wall, if not the new plaster weight will fetch it off... i mix pva 3 to 1... and was the pva tacky when the skim was applied...
 
pva mx sounds a bit weak, try 1 pva/2 water, let first coat soak in then roller 2nd on.depending on how the 2nd coat sucks in maybe put a 3rd on.Or 1 coat of wickes bonding agent, pricey but good stuff
 
for every different room you need a different mix of pva. as all surfaces need a different approch. it would be cheaper to let a plasterer do the work.
 
Could have been many things. What kind of paint was on the wall? Is it an old house with a chalky feel to the paint?
 
Heat , suction , a supose how sloppy ur mix was , windows open etc all can cause things u just have to be aware of them and keep a eye on how ur plaster is going
 
Iotrez said:
I put the PVA on the painted wall before plastering.

After looking at the wall again, I'm starting to wonder if the problem was the the old layer of finishing plaster was not well bonded to the wall and that my new layer just come off with that.

maybe I should have tried to take off the original layer of finishing plaster?

Do you normally skim straight over an old layer of skim, or should you try to get back to the undercoat of plaster first?

Thanks.
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give the original finishing a good scrape get the scraper in the back of it get all the loose stuff off. before re skim.check if the wall is boss.
 
i normally mix sand through the pva then apply with a roller the day before skimming nice key to work off and no slides
 
Iotrez has gone. If it had fallen off again he would have been back already.

He could have least come back to say thanks to everyone. Some people....
 
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