Plaster/tiling question...

Sharra

We recently took some tiles down and had to replasters a small area (about 12" x 12") cos it was a bodge job underneath. We used the ready mixed plaster from a tub.
Now I need to retile the wall - do I need to seal the plaster with something before I tile, or can I just tile over the top?
Any help appreciated.
Many thanks
Sharra
x

Alan_M_2

It depends which adhesive you're using, it will generally say on the packaging.

As a rule of thumb, if you're using a ready mix adhesive from a tub then more often than not you don't require a primer.

If you're using a cement based adhesive (a powder that you mix with water ) then you will need a primer, basically to stop a chemical reaciton between the cement adhesive and the plaster.

Don't use PVA. Diluted or in any form.

woodbutcher_2

I've seen that mentioned before on this site about not using pva.I have used it all my working life for a variety of tasks including tiling and have never had any problems with it(to my knowledge anyway)so why shouldn't it be used.I am not saying you are wrong,i'm just curious.

Alan_M_2

Click the following link, it takes you to a post giving more detailed reasoning.

I'm the author of that post and I post on a few sites similar to that under the name Mudster.

It's more relevant now as tiles become larger and larger, therefroe thicker and heavier and approach the weight limits of what is suitable to fit on plaster walls. Old Crystal or HR Johnson tiles weigh so little it's ulikely to have been an issue.


http://www.ultimatehandyman.co.uk/forum1/viewtopic.php?t=168

woodbutcher_2

Interesting.I suppose i have never come a cropper because i don't do a great deal of tiling and it is usually small stuff in kitchens and bathrooms.I always use BAL adhesive and grout as i think it is a quality product.I will look into using their primer in future,thanks.

Alan_M_2

BAL is a quality product, which is probably why you've never had a problem, and using PVA doesn't gaurantee failure but it certainly doesn't help.

Use BAL APD as a primer, not the cheaper SBR which is a slurry primer for dusty concrete floor etc. Worth the extra pennies and it goes off in 20 minutes so no real hanging around.