Preparing Bathroom Walls For Multipanels

[WSB]

Just prepping my walls ready for attaching mutipanels.
I know the multpanels are waterproof but was more thinking about creating a good surface for sticking the boards to the walls with adhesive.
The walls aren't brilliant.
Was thinking about painting them with watered down PVA?
But noticed there are some special products out there like AquaDefence.
Presumably as these products are made for tiling on, I guess that the multipanel adhesive will work just as well?
Also, is it worth getting the multipanel brand adhesive or will grip fill etc do the job?
Thanks!!!

 

[Bonni]

The wall background is either low suction or high suction. High suction means, it sucks the moisture out of the filler/plaster/adhesive etc.. for those to work correctly. Use 50:50 PVA or SBR and brush the walls where you are going to fit the boards.

Some board manufacturers will claim they can 't give you the warranty unless you use their stuff. Gripfill will do the job, avoid the water based stuff. I always use Fix All and the board manufacturers version appears to be the same.

 

[WSB]

Just seen the Mapei Shower Waterproofing kit in Screwfix. Looks like it could be good to use.

 

[Madrab]

Just seen the Mapei Shower Waterproofing kit in Screwfix. Looks like it could be good to use.

Very good DIY tanking kit and will seal the surface nicely. Just make sure the wall is totally dust free.

 

[WSB]

Getting the wall totally dust free might be tricky but I'll do my best.
As I'm fitting waterproof multipanels over the top, waterproofing the walls might be a bit overkill, but I want to go belt and braces on this one.
Thanks!

 

[Madrab]

What is the wall covering? Is it plaster? make up a loose mortar slurry in a bucket, spray the wall with a spray bottle till it's wet and paint the slurry on the wall and let it dry, that should stabilise the surface.
If the wall is dusty then nothing will take to it properly until it is.

 

[WSB]

It's not really plaster. More of a sandy rough type of plaster.
Would coating the dusty wall with watererd down pva first help?
Thought that it would soak into whatever is there, then create a dust free surface to paint the waterproofing stuff onto.

 

[Madrab]

Only issue with PVA is that it's primarily water based, one reason why professionals are shying away from using it as a primer/sizer these days, not good in wet areas.

Most of the tilers/decorators I talk to won't use PVA any more. When any adhesive, especially water based, is used, it 'reactivates the PVA' loosening the grip it's supposed to provide. Therefore they can't guarantee the finish and a lot of the adhesive manufacturers these days won't provide a guarantee if PVA is used.

A cementous/mortar based slurry - consistency of tomato soup - painted on will, once dry, be as good as waterproof and super stable. If you don't want problems in the future then it needs good prep.

 

[WSB]

Fair enough. Thanks!

 

[Bonni]

Only issue with PVA is that it's primarily water based, one reason why professionals are shying away from using it as a primer/sizer these days, not good in wet areas.

Most of the tilers/decorators I talk to won't use PVA any more. When any adhesive, especially water based, is used, it 'reactivates the PVA' loosening the grip it's supposed to provide. Therefore they can't guarantee the finish and a lot of the adhesive manufacturers these days won't provide a guarantee if PVA is used.

A cementous/mortar based slurry - consistency of tomato soup - painted on will, once dry, be as good as waterproof and super stable. If you don't want problems in the future then it needs good prep.

No, PVA / SBR are to change a high suction background to a low suction background. The City & Guilds course in plastering will teach you that. A high suction background robs the moisture out of the product you're trying to use. For example, a decorator would put a mist coat on a newly plastered wall before using filler. Use filler on new plaster and you will soon find out why.

New plaster, you would change it to a low suction for tile adhesive, unless you use White Star. Decorators don't use PVA because you can't sand it, it roughs up.

 

[Madrab]

No, PVA / SBR are to change a high suction background to a low suction background. The City & Guilds course in plastering will teach you that. A high suction background robs the moisture out of the product you're trying to use. For example, a decorator would put a mist coat on a newly plastered wall before using filler. Use filler on new plaster and you will soon find out why.

New plaster, you would change it to a low suction for tile adhesive, unless you use White Star. Decorators don't use PVA because you can't sand it, it roughs up.

Not sure what you mean by no?

I appreciate that it's to do with suction and stops virgin plaster from sucking the moisture out of adhesives. Also, I am not a plasterer, tiler or decorator but everyone I talk to who is, tells me they never use PVA as a primer/sizer as it can only cause problems.

No tile adhesive/wall paper paste manufacturer will guarantee their product if PVA is used as a primer. Any straight search online and in DIYNOT's decorating forum also suggest that PVA is not a good idea to be used as a primer/sizer as it can actually impede cement based adhesive setting properly due to the acetic acid it produces.