Pva dilemma - TilersForums.com

[Richrich123]

Hello,

Would appreciate a bit of advice please. Have had a lot of building work done and the bathroom has been plastered to a keyed hardwall finish. The plasterer knowing it was being tiled floor to ceiling left it at keyed hardwall saying there was no point doing a final finish if just tiling it.

One of the labourers then came along and seems to have pva'd it. Probably thinking he was helping and not realising there was no plan to put a final finish coat on

So I currently have 4 walls finished with a keyed hardwall and with a coating of pva (no idea what mix % of pva they put on

I have gone back to the builders who have now done and left and quesried this and they have said it's fine to tile onto hardwall, just use some sbr to seal it first.

I pointed out it had already had pva applied and they seemed to think it would still be fine and said to put the sbr over the pva.

It's a big room and floor to ceiling so I don't want to risk tiles dropping off in 6 months so would appreciate any advice.

 

[Rich Midge]

I think I'd be glueing and mechanically fixing boards or put a finish coat on though you'll then have to wait a couple of weeks to tile if you skim it. Alternatively sand it back. Is the surface porous still? What tiles are you planning on fixing?

 

[JMC tiling]

Think i'd also be concerned about the weight of the tiles you are using on them walls because the hardwall/bonding is not really suitable to tile onto anyway and your relying on the bond between the substrate and the hardwall being solid enough to take the tiles. Do you know what tiles are going up? is it possible to overboard the bonding with a tile backer board glued and screwed?

 

[Richrich123]

Hi, sorry forgot to say the tiles are ceramic and 300 x 500. A pack 1 sq m is 14.5kg

 

[JMC tiling]

ah ok, then you will be ok on a plastered wall so I would get it skimmed and then SBR the plaster once fully dried if overboarding is not possible.

 

[Richrich123]

I think having it finished with a final skim would be a better option than boarding/tile backer. It would certainly be cheaper to have it skimmed than boarded.

So sounds like it would be risky to put sbr over the pva and hope it would be ok?

Would rather spend £200 for a final skim over than spend a few days tiling and have them start falling off in 6 months. Just a balance as want to get on with it but a new skim is going to be a few weeks wait for the plasterer and then a few weeks to dry out.

 

[JMC tiling]

I don't think i'd be happy putting SBR on a wall that has already been PVA but there may be others with a different opinion on here. Like I say, the proper job would be to overboard using a suitable tile backer board but I guess it depends on how much your budget is. Its always a bit of a risk tiling on skimmed plastered walls as your relying on the plasterers creating a good bond between substrate and plaster and you could be in a situation 6 months down the line where the tiles are coming off with the plaster but to be honest by the sounds of it your putting up fairly light ceramics so not something i'd lose to much sleep over. Hope this helps and goodluck.

 

[J Sid]

reply I got from weber Technical this summer when the plaster on a job didn't believe you can't tile to it

Hello Julian,
We would recommend that the plaster has a finished coat prior to tiling.
It is a stronger finish, we have no recommendations for a bonded layer as it is not within British Standards.

Best regards

but then you have to watch the tile weight

you should be ok with you tiles at 14.5 kg a Mt plus about 5kg Mt for adhesive and grout

 

[Richrich123]

Thanks for your advice everyone. As the hardwall is well keyed a final skim coat should hopefully be pretty strong and given my tiles aren't too heave hopefully that sounds like it should be ok.

Thanks.

 

[Rich Midge]

Agree with the above comments. You certainly won't find a pro willing to tile onto any undercoat plaster. If time is the issue, board it, if can wait, then skim it. Leave to dry before priming and fixing. I would never prime over pva, unless it was a really weak mix chances are whatever primer you use would/could form a skin.

 

[Flintstone]

Best solution here - have it skimmed. The fact that they have put pva on is almost irrelevant as it wanted skimming anyway.

 

[widler]

Skim it then tile

 

[lmkitchens]

I recently had a massive barny with a plasterer.

They left a job after me telling the builders it needed boarding or skimming as bonding. I refused to tile it, even had to call British gypsum up to prove it as I was being labelled a lair!

Only issue is that by the books its 14 days before you can tile it.

 

[Flintstone]

Here's one I refused to tile earlier

 

[Spare Tool]

Bit late now but when it was back to block best option would have been to dry line room and tile straight on to green plasterboard, much as I appreciate there are some good plasterers out there, I happen to know ONE nothings ever as flat or square as a properly dot and dabbed boarded room..