Tiling onto Plywood

I'm about to put ceramic tiles onto the splashback behind the kitchen worktops, up to the underside of the cupboards. Currently there is 18mm standard (ie not external grade) ply boarding securely fixed to battens on the wall, and I'm planning on tiling straight onto the ply.
All the "tiling onto ply" advice I've found on google is about floors. Flexing under load isn't going to be my problem, just want to make sure the tiles stick, although tile adhesives for wood all seem to be the flexible sort anyway. There's conflicting views on to PVA or not to PVA the ply first. To my mind, why PVA seal the surface first when you want the adhesive to "soak in" a bit before it sets (or crystallizes) to get good adhesion, but there may be something I'm missing.
Any views?
David.
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I panelled out a bathroom with WBP ply and tiled over it "some years ago". The ply was sealed with a slow-cure epoxy sealant recommended for use when constructing plywood boats. It was probably overkill but I had terrible problems some years previously when a so-called professional used plasterboard to construct a shower enclosure and tiled over the plasterboard. Deficiencies in his workmanship allowed water to seep behind the tiles and soon tiles were crashing from the wall into the shower cubicle.
I've had no tiles fall off the plywood shower enclosure, nor has it ever leaked. So although it cost more money up front I reckon it was worth it.
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On 7 Feb, 14:06, % snipped-for-privacy@malloc.co.uk (Steve Firth) wrote:

Better done, these days, with a tanking kit if you are using ply, or better still use wediboard instead of ply in the first place.
But anyway, that's a wet area. This is a kitchen wall, so using epoxy (or wediboard) would be pointless overkill.
To the OP, call the manufacturer's technical people if you want a more definitive answer - they have systems for everything (and they aren't necessarily just sales ploys - BAL have told me not to use their APD primer, or any primer, with one of their tile-to-timber products in the past).
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DavidM wrote:

Standard shed tile adhesive sticks to anything I've ever used it on, including blockboard and ply although, judging by a recent post, the Wickes version may be the exception. The fact that tiles stick very well to each other suggests that low/no porosity doesn't affect adhesion.
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DavidM wrote:

Nothing special GOOD quality WALL adhesive will be fine. Wood is a nice porosity - the tile cement dries reasonably quickly, but not too quickly.
Probably the best surface to tile to, actually.

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I went into this in detail recently for a cloakroom project - similar issues.
There were other issues of different substrates and after a lot of looking I concluded that Ardex has the best range of solutions and technical assistance from their helpline.
For plywood, their solution involves a two part binder/primer which is applied and provides correct surface for a wide range of their adhesives. Even after curing, the binder has a tacky surface for some days and gives good grip even for very heavy tiles.
Ardex is certainly not the cheapest product range in the market, but it is well supported in terms of technical help on what to use and it works. Considering the cost of tiles and the time taken to get a layout correct and do the job properly, the adhesive price is not so important.
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wrote:

Thanks to everyone, very helpful. David.
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