JohnD Thanks for the advice about avoiding a spread with sponge or cloth. I will go for the warm spray and keep the scraper clean. Can’t do much until tomorrow night but will feedback the outcome on Wednesday.
Help! Rescuing PVA glue stained skim plaster?
- Thread starter mrburns2010
- Start date
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Invisibly joining a stud wall to a solid block/brick wall can be problematic & unless it’s done correctly, differential expansion of the two wall materials will mean it will always crack around the join; do you know how the join was prepared? Did the plastering involve a base coat & skim or was it just a skim over the original wall & abutted stud wall?
By far & away the best method to join a stud wall to block/brick is to cut the original plaster back to block around 300mm & extend the stud plasterboard to overlap the block wall, fill any gaps with Bonding plaster, reinforce the join & skim over the whole lot.
I contacted the plasterer and he came back to discuss the PVA issue. He insists that PVA is the way to seal the walls and then a final coat. He offered to do the paint job and said I would only pay him if the paint stayed on for a month. I tried every way possible to explain the reasoning between applying an oil based undercoat to the PVA areas and then emulsion over with two coats of undiluted Dulux Mat Emulsion. .
I explained that the difference between the two paints was that the oil based undercoat did not contain water therefore it would not turn the PVA to “sludge”. He agreed it made sense but still insisted that PVA was ok and he had never had a complaint about it in 20 years. I told him I would Email a link to this site and he could make his point here. I have to say that I believe he does actually think he is right and that he is not deliberately trying to con me. That said I still have a problem to solve and I have one more question before I buy in the materials. How is it that water based Zinnser works and does not sludge the PVA. I do not want to buy the wrong Zinnser. I plan to cover the whole 800 Sf Ft so 7.5L is probably right?
I explained that the difference between the two paints was that the oil based undercoat did not contain water therefore it would not turn the PVA to “sludge”. He agreed it made sense but still insisted that PVA was ok and he had never had a complaint about it in 20 years. I told him I would Email a link to this site and he could make his point here. I have to say that I believe he does actually think he is right and that he is not deliberately trying to con me. That said I still have a problem to solve and I have one more question before I buy in the materials. How is it that water based Zinnser works and does not sludge the PVA. I do not want to buy the wrong Zinnser. I plan to cover the whole 800 Sf Ft so 7.5L is probably right?
I can only speak from experience, but on the odd occasion that I have used PVA to seal new plaster, I too have not had any problems.
However, I agree that it's certainly not the best sealer, nor is it recommended by the manufacturers, for use with water based paints. I would never use it between coats of emulsion either.
However, I agree that it's certainly not the best sealer, nor is it recommended by the manufacturers, for use with water based paints. I would never use it between coats of emulsion either.
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How is it that water based Zinnser works and does not sludge the PVA. I do not want to buy the wrong Zinnser. I plan to cover the whole 800 Sf Ft so 7.5L is probably right?
Anybody know the answer to this one? I am going to B&Q today to look at the options including an oil based undercoat.
Anybody know the answer to this one? I am going to B&Q today to look at the options including an oil based undercoat.
To be honest, I don't know whether it does or doesn't.
Zinsser seems to be regarded by some as the answer to everything, but I have just gone through all their priming products http://zinsseruk.com/shop/ProductList.aspx?cId=130 and none actually say they are suitable for covering PVA.
Thanks misterhelpful kind of you to do the research much appreciated. I know from the posts here and in other threads that many of the older hands swear by "good old fashioned oil undercoat" I am going to experiment (oil undercoat) with an area that will be behind curtains and just so everybody knows I am not in the blame game my plasterer is joining in to see what we learn together. I will feedback if there is anything worth posting
Using a wet sponge to remove unwanted PVA does work.
Only used this method in the corners to remove unwanted PVA from the previously skimmed walls. Ie at either side of the newly skimmed wall. And only very soon after the wall has been skimmed, so the adhesive hasn’t been sitting on the wall for days.
Just use plenty of clean water and keep cleaning the sponge in clean water. Yes it takes a lot of water and expect a bit of a puddle at the bottom of the wall but the sponge method does work. Using plenty of water will avoid the possible smearing, which would be a distinct possibility. Try two sponges, one for initial work then another for final cleaning. I suppose the secret is – plenty of clean water to remove any traces of left over pva.
Only used this method in the corners to remove unwanted PVA from the previously skimmed walls. Ie at either side of the newly skimmed wall. And only very soon after the wall has been skimmed, so the adhesive hasn’t been sitting on the wall for days.
Just use plenty of clean water and keep cleaning the sponge in clean water. Yes it takes a lot of water and expect a bit of a puddle at the bottom of the wall but the sponge method does work. Using plenty of water will avoid the possible smearing, which would be a distinct possibility. Try two sponges, one for initial work then another for final cleaning. I suppose the secret is – plenty of clean water to remove any traces of left over pva.
Nige F You are a big fan of 123 and you have used it on powdery walls Etc... Have you ever actually used it to seal PVA and if so how did that go?
For anybody with the same problem I finally went with one coat of Dulux Oil based undercoat...worked perfectly and the room looks great now that we have finished off with Dulux White Emulsin and a colour emulsion for the walls
Several weeks gone by no sign of any peeeling or stains.
Thanks to all you guys who offered help ...very much appreciated.
Several weeks gone by no sign of any peeeling or stains.
Thanks to all you guys who offered help ...very much appreciated.
Good to hear. The reason why PVA is useless is because it just lays on the surface. OK it seals just enough to give a nice surface for NEAT emulsion and all will appear good untill later's when emulsion has cured, and someone bangs wall with broom handle etc = chips, worse if you decide to paper probably to hide horrible brushmarks from using NEAT emulsion, when you come to strip you will find half the emulsion comes away with the paper and will be left pondering whether to reskim or line or ~~~ 
Ps I'm a bit worried about zin 123. used loads in my time but just lately (voc10 fkups ???)
Ps I'm a bit worried about zin 123. used loads in my time but just lately (voc10 fkups ???)
Hughmac
I have the same problem with the PVA stains. I painted a second coat on emulsion thinking it would cover over given the first coat, but it's only made it worse by having a touch noticable edge between the two coats of emulsion and none on the glue.
Did you apply the undercoat directly onto the PVA stain? i.e., I'm assuming that you didn't sand back first, else it becomes a standard wall which you can emulsion over directly?
And how did the emulsion go over the undercoat? It didn't slide around, did it? Did you need to put more coats over the undercoat to ensure it wasn't noticable against the rest of the wall?
I have many splodges (some drips and some where the plasterer seems to have painted the PVA one (!)) and the thought of sanding all of those back would break me..
Thanks..
I have the same problem with the PVA stains. I painted a second coat on emulsion thinking it would cover over given the first coat, but it's only made it worse by having a touch noticable edge between the two coats of emulsion and none on the glue.
Did you apply the undercoat directly onto the PVA stain? i.e., I'm assuming that you didn't sand back first, else it becomes a standard wall which you can emulsion over directly?
And how did the emulsion go over the undercoat? It didn't slide around, did it? Did you need to put more coats over the undercoat to ensure it wasn't noticable against the rest of the wall?
I have many splodges (some drips and some where the plasterer seems to have painted the PVA one (!)) and the thought of sanding all of those back would break me..
Thanks..
Hi - my other half is having exactly the same problem with a hall, stairs and landing covered in glossy pva-brushed filled cracks that the plasterer came back to repair once our initial replaster had settled and cracks opened up.
Hours and hours of sanding and filling have still revealed streaks coming through two coats of diluted trade emulsion....it comes through - he sands it and repaints it, it looks like it's gone and a few hours later there the streaks are again...
He's really loathe to now coat all the (seal painted) walls in oil-based paint to now try and seal, especially as the final two coats going on the top will be a Farrow & Ball paint which is decidedly chalky and matt in finish so apart from the strong smell (there's a lot to cover) he's worried that the gloss will show through and give an odd effect.
He wonders could he use some sort of gloss spritz/spray mix just over the patches so he seals it but doesn't end up with an odd-looking gloss brush patch in certain areas?? Or which of the Zinsser products are the ones you chaps have used over your PVA nightmare? Could he now paint this product just over the emulsioned patches as they show through??
He's done the top floor and landing (loft conversion) so far - the downstairs hall and stairs are still bare plaster and loads of PVA-ed cracks so theoretically he could then use whichever Zinsser product anyone recommends on the bare plaster down there before starting with the diluted initial emulsion seal mixes....
Many thanks - we are both in utter frustration here so any help and advice would be really appreciated!!
Loulou
Hours and hours of sanding and filling have still revealed streaks coming through two coats of diluted trade emulsion....it comes through - he sands it and repaints it, it looks like it's gone and a few hours later there the streaks are again...
He's really loathe to now coat all the (seal painted) walls in oil-based paint to now try and seal, especially as the final two coats going on the top will be a Farrow & Ball paint which is decidedly chalky and matt in finish so apart from the strong smell (there's a lot to cover) he's worried that the gloss will show through and give an odd effect.
He wonders could he use some sort of gloss spritz/spray mix just over the patches so he seals it but doesn't end up with an odd-looking gloss brush patch in certain areas?? Or which of the Zinsser products are the ones you chaps have used over your PVA nightmare? Could he now paint this product just over the emulsioned patches as they show through??
He's done the top floor and landing (loft conversion) so far - the downstairs hall and stairs are still bare plaster and loads of PVA-ed cracks so theoretically he could then use whichever Zinsser product anyone recommends on the bare plaster down there before starting with the diluted initial emulsion seal mixes....
Many thanks - we are both in utter frustration here so any help and advice would be really appreciated!!
Loulou
If you’re thinking of having your downstairs replastered, employ a different plasterer, sounds like the one you had hasn't got a clue!
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