The plasterboard should be sealed with a tanking product
for the purpose. PVA is not suitable (it's not waterproof).
Look at something like BAL WP1 Tanking.
Lots of people do tile directly onto plasterboard without
any problem. If you do this, I would suggest adding a
waterproofer/plasticer to the grout, such as BAL admix
If you haven't yet put the plasterboard up, look at using
cement based aquapanel instead.
[email address is not usable -- followup in the newsgroup]
I'm just about to start a bathroom tiling job too and had the same initial
question. In my case, the entire bathroom is going to be tiled and it's
costing me a fair bit in materials so I want to get it right. Could someone
clarify the following given that I'm not about to start ripping off all the
plasterboard and replacing it.......
1. Is it best to use a waterproof sealer through the entire bathroom or just
where the tiles will get a drenching (i.e. in the power shower). If its OK
to use some other sealer elsewhere, what would you recommend?
2. In the areas where previous tiles have been removed in the shower
cubicle, the surface is still very slightly powdery in spite of a good clean
down. This is because the paper finishing surface of the plasterboard has
torn off in places where the adhesive was, leaving the paper exposed to
catch dust. Will this stuff still bind and stabilise such a surface, or is
some other prep necessary?
3. I've seen references to tape and matting in connection with the BAL
tanking products. Presumably the tape is waterproof stuff for sealing
corners but what is the matting used for?
4. I think I've read somewhere that a waterproof coating can be applied to
certain types of tile AFTER they have been put up. Is this right, and if so:
In my last house I removed the 25year old bathroom tiles from plaster board
(handy they print date on plasterboard) and there was no sign of water
penetration of dampness and it looked like just normal adhesive and grout
had been used. I simply replaced the board and tiled again this time using
waterproof adhesive and grout. Worked fine.
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