Pva Versus Primers | Always Use A Primer When Tiling, And Not Pva

[julie67]

Re: P.v.a. Versus Primers......

hi luvlies, im on a course at the moment and last nite Steve who runs the course advised the same, use a primer and not PVA. see I learned something lol x

 

[dock]

Re: P.v.a. Versus Primers......

As another responsible UK adhesive manufacturer, MAPEI, we concur with the views of Bal, Ardex and Nicobond. In addition the primers offered for the purposes of "sealing" a substrate prior to tiling by adhesive manufacturers are generally acrylic co-polymers that once cured do not become "live" when the adhesive is put on top.

Dock

 

[Deleted member 1779]

Re: P.v.a. Versus Primers......

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]

Re: P.v.a. Versus Primers......

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

 

[macc]

Re: P.v.a. Versus Primers......

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]

Re: P.v.a. Versus Primers......

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]

Re: P.v.a. Versus Primers......

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]

Re: P.v.a. Versus Primers......

top post.:4:

 

[Deleted member 1779]

Re: P.v.a. Versus Primers......

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

 

[fitzer]

Re: P.v.a. Versus Primers......

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]

Re: P.v.a. Versus Primers......

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]

Re: P.v.a. Versus Primers......

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

 

[Eddie]

Re: P.v.a. Versus Primers......

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?:huh2:

 

[Jv40]

Re: P.v.a. Versus Primers......

sWe

Your guides are... fantastic, superb, marvellous, knowledgeable.... :hurray: I think I've found them all now. My tilersforums.com 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!

 

[White Room]

Re: P.v.a. Versus Primers......

I've done site work for a contractor and never saw a bottle of primer although everything was dry lined, On a another job the walls was bucket gear (some tub gear state that no primer required) and that was on new plaster in a new private housing, Again no primer supplied. If your using cement addy on walls then it must be primed. I've used a mist coat of emulsion, artex sealer and sbr before and had no problems. The trouble with new plaster it's so absorbent and sucks the moisture from the adhesive giving it no time to cure properly, Thus giving in to failures at a later date.

 

[Viceroy]

Re: P.v.a. Versus Primers......

I,m totally confused with this !
I always used to pva diluted 1-4 plywood overlays (Never Had A Floor Fail)
then i was working with another tiler who used bal bond !
I Thought it was much better,so i started using that .
Talking to another tiler about it ,he told me the bal instructions on back of floor adhesive state you should only seal the sides and back face of ply ?
I now can't bring myself to tile directly onto a newly plyed floor without priming it !!!!!! so what do you fellas do on a newly plyed floor bond or no bond ?

Cheers

Viceroy

 

[DHTiling]

Re: P.v.a. Versus Primers......

BAL say you don't need to using there cement adhesives.......but other manufactures will say to prime...so always check on the bag.......

 

[Viceroy]

Re: P.v.a. Versus Primers......

Think youre right there !
Because Flexible profix (Dunlop) Say to use suitable primer !
Next job is with PCI
Tilefast 6 Rapidflex

The surface should be prepared to provide a rigid and secure base without deflection and suitable to support the
intended weight. Tongue and Groove/Chipboard must be over-boarded with exterior grade plywood which is at least
15mm thick and given time to find equilibrium with its surroundings. Plywood floors must be 18mm thick and all joints
must be supported. All must be screwed down every 300mm centers. The reverse face and edges of the boards must
be primed with Primer W to prevent the ingress of ambient moisture while the exposed face should be unprimed and
clean. Any existing wooden floor may also be over boarded with PCI Pecidur: minimum 10mm thick or PCI Polysilent:​

4mm or 7mm thick

Still not convinced about no primer !!!

Viceroy

 

[DHTiling]

Re: P.v.a. Versus Primers......

That also sez no primer...trust me i use BAL day in day out and it is fine......

Like i said if it sez prime then prime it if not then don't.......🙂..

 

[Viceroy]

Re: P.v.a. Versus Primers......

Cheers Dave !

 

[sWe]

Re: P.v.a. Versus Primers......

Many/most modern cement based adhesives are "primer free" to some extent. That means they don't require normally encountered surfaces, such as plasterboard or concrete, to be primed, BUT, there are almost always exceptions. The obvious ones are gypsum/anhydrite surfaces, (partly for the reaction risk, partly because they're very absorbant) and other surfaces which may react in some way when in contact with cement based materials.

Very absorbant or very non-absorbant surfaces may need to be primed.

Very absorbant surfaces can include certain light weight concretes and LECA, because otherwise they'll absorb too much moisture from the adhesive, thus preventing it from curing properly.

Very non-absorbant surfaces include already tiled surfaces, plastics, and metals, becuase the adhesive may not bond properly to them otherwise.

Always check the manufacturer instructions on wether or not an adhesive is suitable for the surface you intend to tile, and if your specific surface needs priming or not when using your chosen adhesive. It should say so on the bag. If it doesn't, don't risk it.

 

[dptiling]

Re: P.v.a. Versus Primers......

the pva my tile shop sells .has pva sealer and pimer on the front.
confused dot com or what.:confused_smile:

 

[Gazzatile]

Re: P.v.a. Versus Primers......

Dave very good article hopefuly this will mean fewer jobs failing

Gazza

 

[handyrabbit]

Re: P.v.a. Versus Primers......

brilliant! saves me asking the question why!!

glad i've moved house - pva'd a wall in my bathroom b4 tiling it!!

was there for 3 years after but i wonder mmmm???!!!

 

[David - Tradetiler]

Re: P.v.a. Versus Primers......

Just in case anyone missed it, because of this thread, we now stock SBR (at a really good price too) :yes:

[DLMURL="http://www.tradetiler.com/acatalog/siliconing_tiles.html#aSBR"]TradeTiler.Ltd Siliconing sealers/primers[/DLMURL]

 

[pt44]

Re: P.v.a. Versus Primers......

So, have I understood correctly - that SBR is a proper primer? not a PVA.

Also - from the small plastering knowledge and mortar knowledge that I have. I would normal pva seal a brick wall, with 1:4 pva mix. Let it dry, then redo it, with a 1:1 pva mix, and either plaster over it or render it with mortar, while the second mix is still tacky.

Can't beat PVA for plastering/rendering & patching in mortar or concrete (from my experience)

However, really interesting about why not to use it for Tiling.

Paul

 

[White Room]

Re: P.v.a. Versus Primers......

I don't use pva if I'm rendering a wall, I will dampen the brick wall with water then render but if has any variation of finishs on the wall then sbr or cement slurry.
PVA for plastering though

 

[GazTech]

Re: P.v.a. Versus Primers......

DESCRIPTION
A water-based dispersion of a styrene-butadiene copolymer with a
wide variety of uses in the construction industry, particularly as an
admixture and bonding agent for cement and concrete applications.
Once cured, the polymer is water and frost resistant.
January 2005
Cl/SfB
Yt4
APPLICATIONS & PERFORMANCE
BAL BOND SBR
USE & SERVICE CONDITIONS
BAL BOND SBR can be used as a slurry coat when mixed with hydraulic cement or gypsum plaster; as a multi-purpose admixture for
cement:sand mortars, concrete and gypsum plaster; as a brush applied primer, sealer or dustproofer.
STANDARDS
The high quality of this product is maintained through a stringent internal
quality assurance system conforming to BS EN ISO 9002 with regular
external quality assessments by independent authorities such as BSI.

 

[pt44]

Re: P.v.a. Versus Primers......

Waterproof PVA?

Ok, so normal PVA is no good, as it goes back to being glue if you add water, once it has dried. However, Waterproof PVA? What is it. Surely, the fact that it is waterproof means that it must have something in it - that stops it doing that. i.e. it must form a stable substance, that is not affected by water.

That then surely, is the same as SBR or a primer?

Or is it? Anyone?

Paul

 

[DHTiling]

Re: P.v.a. Versus Primers......

Tilers Primers stop a reaction with gypsum and cement based adhesives.( Ettringnite )..PVA won't do that.....stick with tile primers...can't see whats hard to understand here.....

 

[grumpygrouter]

Re: P.v.a. Versus Primers......

Sounds to me like we need to recruit a Chartered Chemist if we start getting techinical posts like this more regularly!