I have to tile a shower area which the biulder has previously coated all over with PVA for some unknown reason. The surface is plasterboard on one side and plasterd mortar on the other. Can I tile over or can i use a primer over the pva.
thanks

No, you will need to remove the pva somehow. Try dampening it down 'til it reactivates and then use a scraper to remove as much as possible.

dont over dampen the plasterboard though.

http://www.tilersforums.co.uk/tile-a...?highlight=pva

print this of and show it to the builder!

Thanks for the advice-looks like i will have to remove as much as i can
cheers

Originally Posted by a hope

Thanks for the advice-looks like i will have to remove as much as i can
cheers

could try a steam stripper. Wallpaper type - it will emulsify the PVA quite quickly without damaging the plasterboard behind. You can then scrape it off

the pva should be ok if its watered down alot.this is what i dont get
it should soak into the plaster and will hold the suction enough to let the adhesive bond to the surface until set. if it is NOT diluted enough then i can see the problem of it (skinning) on the surface and peeling off. in 20 year of plastering and tiling ive never had a problem with it.just my 2 p worth and thoughts about this discussion. i do now always use tile primers now just to be safer after reading whats been said on here,but that doesnt mean i agree if its been diluted enough

Originally Posted by ssharpe

the pva should be ok if its watered down alot.this is what i dont get
it should soak into the plaster and will hold the suction enough to let the adhesive bond to the surface until set. if it is NOT diluted enough then i can see the problem of it (skinning) on the surface and peeling off. in 20 year of plastering and tiling ive never had a problem with it.just my 2 p worth and thoughts about this discussion. i do now always use tile primers now just to be safer after reading whats been said on here,but that doesnt mean i agree if its been diluted enough

PVA does not prevent ettringite failure..primers do...and the old phrase i have never had a problem does not say it is right to use it does it..?....

ha ha yea dave
its just id like to see someone trying to steam off pva thats been watered right down and soaked into a plastered wall,it would be impossible.
it should hold the suction to allow the tile adhesive to bond and set on the surface then if it does start to break down the tile adhesive will be already bonded to the plaster with no adverse effects. it is definately not waterproof as you all know,just my logical thinking about it.might need a scientific test bed done ,ha ha.
ill always use primers from now on tho.

Ssharpe; read this if you've got time:

sWe's guides

good info,so tile adhesive is a cement based adhesive then/pre mixed stuff.

Originally Posted by ssharpe

good info,so tile adhesive is a cement based adhesive then/pre mixed stuff.

PVA still becomes live when exposed to moisture, and no adhesive, except epoxy based adhesive, is waterproof; merely water-resistant. That is an important distinction; resistant means it doesn't degrade when exposed to water, and proof means it doesn't let water through.

It's best to stay away from PVA completely when it comes to tiling. It serves no purpose at all.