I have just had my walls in my bathroom coated with bonding plaster. I am getting conflicting advice as to whether it is ok to tile directly on this surface. Does anyone know whether it is ok to do this? And if not does this mean I have to get the walls skimmed. Any help will be extremely appreciated as I am completely stuck so to speak!
Tiling onto bonding coat is fine.
It may well be, but it isn't recommended practice.
For instance,
relevant... I never use ready mixed adhesive or grout, and in the case of something like a shower, I use a waterproofing admix in the grout (which also helps it stay clean, as well as protecting the backing from moisture).
That's a deliberate statement on their part because of the ettringite problem between cement and gypsum - that's why they are recommending the glue type tub gear.
Maybe Biscem is more persuasive? Page 7 of this:
I use epoxy in showers.
Its fine. It will suck the cement pretty hard though. Some people like to seal with PVA..
Yes you can (as long as it is flat enough!), I have done it several times without any problems.
Done it several times. Always PVA'd it first, since surface can be a little dusty. Simon.
Hadn't you better warn him that you also say that it is fine to tile onto chipboard on the basis that most of yours were fine and only a couple lifted and needed to be replaced with a bit of new sub-floor, or whatever that story was?
It's a bodge, and not recommended. Seal it well. The tile adhesive manufacturers almost universally say do not use PVA but a proprietary acrylic sealer. This may be because they want to sell their proprietary products, but they are insistent on this point.
Preferably use tub gear to avoid future etrringite problems, and make sure your grout is waterproof - epoxy preferably (ignore the scare stories, it is easy to use) or a powder grout with a waterproofing admixture as someone else suggested. 90 something times out of a hundred it will probably be fine anyway, but don't expect any sympathy from the adhesive manufacturer if they do fall off and you haven't followed their instructions.
Next time ask for a sand/cement render base if you are tiling over it.
Thanks for everyone who has given me help on this. I have just completed it directly on the bonding, I'll let you know if any fall off!
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