P.v.a. Versus Primers......

[365drills]

This is great post because I get involved with a lot of builders and plasterers (is that spelt right) who PVA everything in sight.

I've had a lot of plaster work done and the first thing they do is PVA bond the area to prime for plaster.

The problem I had was my bathroom walls were wonky so a plasterer came in and skimmed it.

To fix the skim to the existing plaster he applied a thinned down wet coat of unibond and then went on to skim the wall to get a perfect but thin plaster skim.

THEN the tiler came in, primed the skimmed walls with "proper" primer, (I also used BAL tanking kit on the heavy use area) and he then came back and tiled.

IF there is a point to the post I think it might be that PVA and UNIBOND if used properly (ie by the wet trades when applying plaster) then its a useful boding agent for a builder.

Half my house is unibonded prior to plastering.

Oh yes and one thing I was told (a tip) is never let the PVA dry out. Plasterer said he sometimes goes to a job where the owner has "helpfully" unibonded the area for him a week prior so its dried out. He tells me only wet and week is the only way for it to stick to the plaster and substrate.


[The walls were so wonky a skim coat was applied]

Please tell me if I have got any of this wrong.!

Footnote: Please note words used above describe the same material: PVA, Unibond, PVA Bond,

[GazTech]

Thanks for your valid and true advice dock, and welcome to the forums....Gaz

[macc]

hi everybody im a new addition,
so years ago when people said pva it was talking s...! if i was to tile a wall that was emulsioned in a b/room i would key it then use a primer and that would suffice?

macc

[floydyboy]

Originally Posted by 365drills

This is great post because I get involved with a lot of builders and plasterers (is that spelt right) who PVA everything in sight.

I've had a lot of plaster work done and the first thing they do is PVA bond the area to prime for plaster.

The problem I had was my bathroom walls were wonky so a plasterer came in and skimmed it.

To fix the skim to the existing plaster he applied a thinned down wet coat of unibond and then went on to skim the wall to get a perfect but thin plaster skim.

THEN the tiler came in, primed the skimmed walls with "proper" primer, (I also used BAL tanking kit on the heavy use area) and he then came back and tiled.

IF there is a point to the post I think it might be that PVA and UNIBOND if used properly (ie by the wet trades when applying plaster) then its a useful boding agent for a builder.

Half my house is unibonded prior to plastering.

Oh yes and one thing I was told (a tip) is never let the PVA dry out. Plasterer said he sometimes goes to a job where the owner has "helpfully" unibonded the area for him a week prior so its dried out. He tells me only wet and week is the only way for it to stick to the plaster and substrate.


[The walls were so wonky a skim coat was applied]

Please tell me if I have got any of this wrong.!

Footnote: Please note words used above describe the same material: PVA, Unibond, PVA Bond,

I have been plastering for 20 years now and i plaster over wet and dry unibond the plasterer who told you that is talking through is a-- !!! when skimming over old work i will unibond the day before the reason being the skim will old a lot longer, and when the skim comes into contact with the dry pva it becomes active [live] again it is when you don't dilute it correctly you get the problems to weak does not do any thing and to thick forms a rubber skin over the surface.

[planetdeano]

Interesting stuff about the PVA v Primers. Appreciate this isn't a plastering forum but figured someone out there would have some knowledge. As the advice goes to use pva in order to seal old plastered/painted walls before doing a re-skim. However i've never found this to be ideal and wondered if it would be better to use a Primer as with the tiling argument, If so any suggestion on type of primer
Incidently there would be no tiling involved.......................................... ..................
Also While i'm on was hoping someone would have any advice/contact for tiling wotk in Malta as I'm thinking about heading out that way for a while

Thanks lads/lasses??



edit.....maybe i've found the advice on some posts above

[dptiling]

top post.

[365drills]

Yes this is turning out to be a very useful post.

[fitzer]

Just a quick question dave, what if you suspect walls have already been primed with pva - is there a primer that will counter act this? Also just to note, there are loads of different primers for different surfaces. Handy hint, if a bathroom has been stripped and premixed adhesive has been used if you apply pva bond to it, it will actually make it go soft with a couple of coats and it will come off the wall like butter. You point about pva - I have actually repaired a job where this has happened where a whole wall of tiles literally leaned away from the wall - some sight - sorry I didnt photo it - i normally use the technik evostick primer 918 - any of the brand name adhesives have a list of primers on there web sites for a list of jobs

[Jv40]

What a great thread.

I wonder though is paint-primed new plaster prior to tiling as adequate as an intended tiling primer because I always believed this to be the case, and was told this on my course. Thanks Julia

[sWe]

Here's a small post I made on Cement, Gypsum, Anhydrite, Ettringite Crystals, and PVA.

[Eddie]

I have just been on the Weber site, checking out their gear. and found this. Weber PR370 is a synthetic water-based PVA concentrate. For sealing and priming building substrates.
Seals dusty or porus surfaces prior to tiling. If all concern about pva is justified, thats a bold statment from a company like Weber, or is this a different product all together?

[Jv40]

sWe

Your guides are... fantastic, superb, marvellous, knowledgeable.... I think I've found them all now. My TilersForums.co.uk lever arch is bulging and now has its own sWe Guides section. I'm a huge advocate of technical knowledge, the more I know, the better it must surely make me (imo).

In summary is it correct that contract emulsion for new plaster will suffice but any other substrate should be washed first with say sugar soap or at least tacked down and then correctly sealed?

The builder I work for told me last year that professional tilers do not prime their walls prior to tiling, including new plaster. I couldn't argue with that as I had no idea what professional tilers do, I just knew I had been taught to do it and that was that! He was upset because he told the customer I wouldn't be priming and when I did he thought it made him look an idiot!