Porcelain on external plywood

[bubs]

Hi all, I'm after a bit of advice please on this rather unusual project (for me anyway)
I've got a small section under my front window that I was going to put some PVC cladding onto but while tiling my kitchen splashback I thought the tiles would look good on this section of wall.
Picture below, the wall is made from a 3" frame with 12mm plywood face. The tiles are mat white porcelain brick look (Hartley™ White Tile | Topps Tiles - http://www.toppstiles.co.uk/tprod47076/hartleywhite-tile.html)
(I will be painting the horrid yellow bricks either white or light grey)
Just want to know how some of the professionals would tackle this being both external and porcelain tiles and on wood and if there's even an adhesive/grout that would work. I did some tiling on ply before but that was internal and ceramic tiles.

 

[peteablard]

Can it be replaced with Hardie? Or is there room to overboard with Hardie then tile?

 

[andy8758]

If the ply is not a good quality hardwood ply, it will struggle in an outside environment - the tiles will still allow moisture behind. If you can remove the ply, coat the back, and edges with a good quality SBR primer. Either primed or unprimed I would go for a good quality S2 flexible adhesive. Tilemaster Ultimate, Mapei Ultraflex S2 Quick, and Weber Prolite rapid are all good products.

 

[Flintstone]

If you can remove the ply and replace with wedi board I would do that.

 

[bubs]

Thanks for the replies. The board is just screwed there at the moment so can be taken off and primered/replaced if needed. It's just a stud wall behind with around 30-40mm from studs to brickwork face. I was thinking of putting a vapour barrier behind the ply just incase, but if i can replace the ply with something more suitable then that's fine (so long as it's not stupid expensive ) I like the thought of adding a bit of insulation in there, so could I use something like the tilemaster boards either over the ply or instead of and it still be "solid" ie not going to crack in the unlikely event someone drives into it as the wall is fronting a driveway.
Tilemaster Adhesives Delta Board Thermal Construction Board – Screed Giant | Screed, Insulation & Under Floor Heating Suppliers - https://www.screedgiant.co.uk/product/tilemaster-adhesives-delta-board-thermal-construction-board-6mm/

 

[Flintstone]

Your on the right lines there, there are a few manufacturers of those boards, wedi, delta, marmox, all will do the job you want but don't use 6mm. The thicker the better, I'm not sure what the minimum thickness is for going onto studs, think it's 10mm?

 

[bubs]

Thanks, will have a better look into these

 

[bubs]

Another quick question, would i use the adhesive as the grout too or do i need a specialist external grout?

 

[Flintstone]

Most modern grouts from reputable brands are fine for out doors

 

[bubs]

Thanks again