Is it correct to seal walls before tiling?

[hollywood]

The Bathroom is large, the tiles are very large, the walls are thermolite blocks and plastered, took the wall paper off and their is no paint on the plaster. some of the walls have cracks so chopped out to about 50mm each side of the cracks and replastered, i think their was some settlement and shrinkage when the extension bathroom was built 20 years ago which caused some off the thermolite to deflect and break the bond to the morter bed, no fresh signs off movement and no problems to the external brickwork.
Is it right to use Bal white star flexible adhesive?

Also do i prime the walls with PVA or any other product?

Im going to use a flexible grout probably a Bal water resistant grout.

Some expert advice please!!!!!

 

[Gobo]

If there's no issue now with movement of the wall you wouldn't need to use a flexible, but put piece of mind you might want to.

Definitely seal the wall with a pva mix before tiling.

Bal grout is a good choice.

 

[Richard C]

DO NOT use standard PVA before tiling; it remains water soluble, can give problems with adhesion & if used in a wet area, your tiles may well end up on the floor. If you need to prime use an SBR based primer but always follow the tile adhesive manufacturer’s instructions. With large, heavy tiles you will need a cement powder based adhesive (Rapidset); do not use tub mix. Bare plaster must be primed before using cement based adhesive to avoid reaction between Gypsum & cement.

If the plaster/render on the blocks is blown (sounds hollow when tapped), your wasting your time sticking tiles over the top; it won’t last & the additional weight of the adhesive & tiles may well pull the lot off the wall.

 

[Gobo]

Rich, How would the wall become wet btw? If waters getting behind tiles surely it hasn't been tiled with the correct materials in the first place? Whether or not the pva remains water soluble the problem would lie with the grout and seals? I understand it could be a problem in a wet room but a bathroom?

 

[tictic]

the wall become "wet".. when you apply the cement based adhsive.

op
as richard has already told you prime walls with a primer..not pva.

 

[Richard C]

Rich, How would the wall become wet btw?

I used the term “wet area”; to those in the trade it means an area which is subject to heavy splashing or running water; behind a bath, in a shower enclosure or wet room. Two problems could result from using water soluble PVA on a tile substrate;
1. As Tictic’s post; when you put a water based tile adhesive onto the wall, the PVA will emulsify causing initial problems with the tile adhesive setting and it can make it nigh on impossible to get the tiles to stick.
2. Even when the adhesive eventually sets, water soluble PVA will emulsify if moisture gets to it. This can happen as a result of normal use (see below for definition of “water proof adhesive/grout”), or the slightest crack in the grout/silicone can siphon water behind the tiles, again, causing the PVA to emulsify = tiles on the floor. If the substrate needs priming, an acrylic primer should be used.

If waters getting behind tiles surely it hasn't been tiled with the correct materials in the first place? Whether or not the PVA remains water soluble the problem would lie with the grout and seals?

A very widely held miss-belief is that water proof adhesive & grout is totally waterproof, it isn’t; it’s only waterproof in the sense that is will not disintegrate if it gets wet, it is not impervious to water unless one of the very expensive epoxy products.

I understand it could be a problem in a wet room but a bathroom?

Yes; it can cause problems anywhere that is subject to continual splashing or running water, Christ I see it often enough when I rip the lot out for refurbs. Do some research of your own; read the Tiling Sticky, search the tiling forum archive for sob stories, visit the adhesive manufacturer's technical websites or Google the wider net. for other pro tiling forums. Using soluble PVA under tiles along with un-tanked plaster board in wet areas is bad advice & possibly the biggest cause of early tile failure, usually within 3-5 years. If a job done correctly using good quality materials it should easily last 10 years, up to 20 years or even longer without problems.

 

[Gobo]

This was a reply to tictac, Thanks for the reply Richard.

Well Richard didn't say that he said 'wet area' giving the impression of a shower/wet room. Not that it would become wet from the cement based adhesive. I did also ask him btw, and as for

"as Richard has already told you prime walls with a primer..not pva"

Do I know him? or you? I was just asking a question regarding what he said this isn't my post. And as for telling people what to do on this site well you ought to be careful if that's how you word your replies as this is an advice site and you wouldn't want any come backs for people doing what you told them rather than what you just advised.

 

[Richard C]

Tictic’s response is totally accurate & I’ve just taken the trouble to post a longer reply in an attempt to educate you further. I know very well that Tictic can look after himself but your comments are unnecessary & uncalled for. Some of us on here actually do this sort of stuff for a living you, if you can’t give correct & accurate advice on a subject then don’t post.

 

[Gobo]

educate or bully?

I was quite reasonable tbh, and maybe Tictacs post was totally accurate. All I asked was a question and got bitten. ('How would the wall become wet?')

This is a public forum and people can give and take advise as they please, not get it forced down there throats.

 

[tictic]

This was a reply to tictac, Thanks for the reply Richard.

Well Richard didn't say that he said 'wet area' giving the impression of a shower/wet room. Not that it would become wet from the cement based adhesive. I did also ask him btw, and as for

"as Richard has already told you prime walls with a primer..not pva"

this was directed to the op...have a look again

Do I know him? or you? I was just asking a question regarding what he said this isn't my post. And as for telling people what to do on this site well you ought to be careful if that's how you word your replies as this is an advice site and you wouldn't want any come backs for people doing what you told them rather than what you just advised.

wtf....you TOLD the op to use PVA...

if you dont like the way i reply and give advice,well i couldnt give a flying @@@@.. is that carefull enough for you mate

 

[tictic]

educate or bully?

I was quite reasonable tbh, and maybe Tictacs post was totally accurate. All I asked was a question and got bitten. ('How would the wall become wet?')

This is a public forum and people can give and take advise as they please, not get it forced down there throats.

gobo
think you might want to start reading from the very first post all the way down to this one.......and then come back and tell me were i was.. bully/pushing.. advise down anybody throat????

i await your reply...

 

[Gobo]

I'm sorry Tictac having looked it was for the op to which I now Know is original poster?, my mistake but I do think that how you replied was a little harsh.

I've used pva based products for sealing for quite sometime without any problems.

Thankfully I don't take things like that to heart as I'm sure I probably brushed you up the wrong way and I'm sorry for that.

 

[tictic]

I'm sorry Tictac having looked it was for the op to which I now Know is original poster?, my mistake but I do think that how you replied was a little harsh.

I've used pva based products for sealing for quite sometime without any problems.

Thankfully I don't take things like that to heart as I'm sure I probably brushed you up the wrong way and I'm sorry for that.

gobo
i just say it as i see it,in as few a words as i possible can.
cause my "FINGER" that i TYPE with...."rich now you know"..lol can only take so much...

as for brushing me up the wrong way..i am very thick skinned...
i do like a good "disscusion" ..tho

 

[Gobo]

lol. Thanks Tictac.

Hollywood if you have bothered to read all this cur-fuffle please can I re-direct you back to Richard C's post up at the top somewhere.....

 

[Richard C]

I'm sorry Tictac having looked it was for the op to which I now Know is original poster?, my mistake but I do think that how you replied was a little harsh. Thankfully I don't take things like that to heart as I'm sure I probably brushed you up the wrong way and I'm sorry for that.

Water under the bridge but I don’t disagree.

I've used pva based products for sealing for quite sometime without any problems.

PVA is a godsend to a plasterer, which I am primarily & it’s known as the “plasterers friend” but you should seriously re-reconsider the merits of using standard PVA in a bath/shower room if you want your tiling jobs to go the distance.

i just say it as i see it,in as few a words as i possible can cause my "FINGER" that i TYPE with...."rich now you know"..lol can only take so much...

I can vouch for that; straight but direct facts is what it's about but it can appear a bit brusk. There is only so much time a regular contributor can give & although I sometimes tend go on a bit I can type with more than one finger I also have a "factual approach" & often get accused of the same thing.

Hollywood if you have bothered to read all this cur-fuffle please can I re-direct you back to Richard C's post up at the top somewhere.....

Thanks for that.

& it's Tictic, not Tictac