Can I PVA this yet?

L

Lexeus

New Member
Go easy as I am new to this, please! I live on one of the smaller Canary Islands and the normally hot but windy desert island climate has suddenly hit a 26*c but 60% humid windless week and my plaster is drying slow.

There are big problems getting materials here at the moment so please don’t criticise the materials I am using, too much! I paid a professional to do my other room, and he ended up using plasterboard adhesive mix as the bonding layer because there no other gypsum plaster to do the job.

I have prepped my kitchen wall with non tacky yellow bonding agent, which is basically blue grit.
On a smalI section there was horrible old cracked concrete so I then laid on a 3mmish layer of 90% pure finishing grade plaster (expensive) on that part and embedded mesh (the only type for sale at the moment), that plaster is still grey. I also prepped that grey area with pva, worried about the strong wind tunnel I have due to no windows, so it is well sealed tacky bluegrit. When I was laying it on I moved out of the pva areas where you can see there is white dry plaster (bottom right & top left)

So I did all this 44hours ago and, I was too scared to key it because there is mesh, I had no time to put my next two layers on the wall whilst it was wet as it hung forever because with no wind, mesh embedded and the wall well sealed there was no sucking the moisture out of it and that meant it didn’t go off even after over 4 hours.

my question is can I pva it and go on with my next two coats now?

Or I was thinking maybe I would do a separate mix for that section with pva mixed in the plaster and forget pva directly on the wall?
 

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John j said:
No idea what I.m looking at
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Agree, sounds a mare for the lack of materials.
I’d of done what the local’s do knock it off S&C scratch let it cure then floating coat with a sponge finish. The paint it up after a few weeks.
 
I thought plaster would be stronger and more crack resistant than s&c?

As this was my first post it got held back for moderation, I had a think and realised that the white bits are actually a small amount of plaster I mixed up to see what ratio to water I needed, and I think I took too long adding in extra powder as it is way too soft on the wall, so last night I actually managed to wipe off the white spots with a wet rag and some elbow grease. Luckily I only tried that mix in two spots where there was no mesh&cracks so the mesh should be ok to leave.

The grey parts are properly set hard and it turns out it is a lot drier than I thought, so now the wind has picked up I think I’m going to leave it until this evening, then pva it all again and forget mixing pva into the plaster

One thing I don’t understand is why all the manufacturers advice for the plaster here says to add 0.7ltr water per kg, but I have decided the best mix is no more than 2:1 for sloppy stuff and much easier to lay it on thick at 2.5:1.
It’s like they think everyone is filling plaster of Paris moulds with this plaster.

As long as I am happy to pay the higher price, this 100minute finishing plaster will set just as solid at 1cm total thickness right? It’s not going to cause me problems?
I did consider using the plasterboard adhesive like my plasterer but with my tap water coming out hot, it’s rating as 20min working time was actually less than half and it was solid at 9min
 
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Lexeus said:
A lot of American guys on YouTube like to stick pva in all their plaster before the final skim. It doesn’t seem to be so common in the uk, what’s the issue?
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Can't comment on the USA other than to say that the plaster they use is not the same as what we use in the UK. Obviously, it's gypsum-based in both the UK and the USA, but other than that, they're different.

If you want to mix PVA into plaster, then do as you please, but I wouldn't do it.

Having said that, I concede that I don't know exactly what plaster you're using, over there in the Canary Islands.

@The Apprentice
 
The problem with PVA from a British Gypsum side is quite simply that they have no say in how it’s made so if BG tested it with plaster they could alter the pva. Im pretty sure we are all aware of the different qualities out there.
With regards to mixing it in the plaster, how does it effect the plaster? That’s not saying it does by the way, and before folk say “I’ve never had a problem etc.” it’s just not been tested.
 
Feels like a good idea to put PVA in because it is mentally associated with sticking
But like putting tomato ketchup on soup or a Sunday roast - just wrong
 
Monkey Boy said:
Feels like a good idea to put PVA in because it is mentally associated with sticking
But like putting tomato ketchup on soup or a Sunday roast - just wrong
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My first boss. Plasterer by trade but housebuilder by profession - used to put pva in the mixer sometimes but I can't remember under what circumstances.
 
Stevieo said:
My first boss. Plasterer by trade but housebuilder by profession - used to put pva in the mixer sometimes but I can't remember under what circumstances.
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Well from reading and watching YouTube my understanding is it’s just a cheat to help make the plaster stick without spending time to pva the wall first. The affect on the plaster is to make it thicker and sticky which can be harder to work with if you add too much glue, but it also slows down drying so you have more time to get the skim coat on. The final coat should also stick better to that pva mixed plaster.

I have also read that people who use pva in their skim coat can cause major problems for the decorators afterwards, because the pva makes it sometimes impossible to get the mist coat to sink in properly and peeling of the paint is a serious risk.
 
MakeItSmooth said:
Can't comment on the USA other than to say that the plaster they use is not the same as what we use in the UK. Obviously, it's gypsum-based in both the UK and the USA, but other than that, they're different.

If you want to mix PVA into plaster, then do as you please, but I wouldn't do it.

Having said that, I concede that I don't know exactly what plaster you're using, over there in the Canary Islands.

@The Apprentice
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I don’t know if it’s any good to you in Spanish but here is the plaster I am using :


It is atleast bagged by a factory in Gran Canaria, but I don’t know where it is actually mined. Although it is bright white powder and sets grey. I have found that if you mix 12.5kg and cover the bucket with plastic, after about 2hours you can see a change and it firms up in consistency, but it never actually sets properly until it drys out, even when I put some on the wall after 5hours in the covered bucket, it took another 3hours to start to go hard.

Any advice on the water to plaster ratio? I am measuring by volume and using 1part water : 2.5 plaster, but frankly it seems to be a case of trial and error when knowing what proportions to use with each type of plaster.

I Have the walls fairly level now, I think tomorrow two thin coats and hopefully finished.
If you look at the left hand wall you can see it leans out at the top, that’s exactly what this wall I have plastered was doing. It was a sort of lean backwards where this a reinforced concrete lintel, this little wall has 4 reinforced concrete beams running through it in total!!!

I have this new window sitting between the two beams above and the two below.
 

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Lexeus said:
Well from reading and watching YouTube my understanding is it’s just a cheat to help make the plaster stick without spending time to pva the wall first. The affect on the plaster is to make it thicker and sticky which can be harder to work with if you add too much glue, but it also slows down drying so you have more time to get the skim coat on. The final coat should also stick better to that pva mixed plaster.

I have also read that people who use pva in their skim coat can cause major problems for the decorators afterwards, because the pva makes it sometimes impossible to get the mist coat to sink in properly and peeling of the paint is a serious risk.
Click to expand...
You don't put skimcoat in a cement mixer
 
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