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I'm tiling above the bath. The wall is undercoat plastered with hardwall, not multifinish. It's good and flat, but not polished, as I knew I was going to tile it. Does it need primer or can I use adhesive straight onto the plaster?
And is any particular sort of adhesive better?
(Tiles are 250x400 mm ceramic.)
Thanks.

nearly caught me out there.........answered as if you had a skim on top of the hardwall.

So, are you saying that you only have hardwall as the background for tiling onto? Or hardwall and finish plaster on top?

No undercoat plasters are suitable for tiling on to, British Gypsum state as much in the tech sheets and addy manufacturers will advise the same.

You'll need to skim it first, assuming your tiles are within the recomeded weight limits. As for priming then that will depend on the addy you use, check their data sheets. By the way don't use OVA as a primer for tiling, it's not suitable

I only have hardwall, no finish plaster.

So Colour Republic, if undercoat plaster is suitable for tiling onto, why do I have to skim it first? You do mean skim it with finish plaster?

And yup, I know not to use PVA!

No, he's saying backing plaster isn't suitable for tiling onto, which is right. It's too porous for the tile addy. Have you got room to put some backer/aqua boards up?
And you would want a bagged adhesive too, not tubbed.

You need to put a finish coat on, which is......finish plaster. Then use primer recommended by adhesive manufacturer. Those tiles are too large for tubbed adhesive, so you will have to use a cement based bag adhesive.

Don't forget to allow plaster to dry before priming and tiling onto.

Oh good grief. I wish I'd asked this before I put the bath in! Now I've got to skim above the brand new enamelled bath without making a mess!
Thanks for the info chaps.

Piece of piddly widdly.....................polythene the bath and that will keep the plaster off of it. Just don't drop your hawk or trowel lol.

Done it. Wasn't too bad. Lots of sheets and gaffa tape, not too much mess.
Didn't drop my trowel either!
Now I've got to wait.....how long? Four weeks, I've heard.

Depends on the climatic conditions of the bathroom as to how quick it dries out. See how it is in 5 days, should be fine. Once it is light pink that is your cue to tile.

Hope you unibonded the walls before applying the finish!

Course I did!
I'll leave it a week or so, and see what it looks like.
Thanks for your help!