Ditra on ply with AF200

[humourme2]

Hi, a long time since I have been here but back for some advice/reassurance !
About to tile my kitchen floor (its a very long running project!). The space was a double garage so has a concrete floor on top of which sits joists. Joists are at 400 centres and sit about 60mm above the concrete and are very well supported every metre or so. Its overboarded with 25mm wbp ply and screwed down at 150mm centres. This has been down for years.... and i do mean years! 5 plus !!! So i think you can say its well acclimatised and i would say that it is rock solid.
I already have all the materials I intended to use, just want to check I am not making a mistake. Intention is to put down ditra with AF200 using a B1 notched trowel then tile with Mapei Keraquick with a 10mm round notched trowel and raimondi tile leveling. The tiles are 600 square rectified porcelenosa tiles.
The floor is about 25sqm and is an irregular shape but the longest run of tiles is 6.5m and across the width 4.4m.
So is my proposed method going to be ok ?
Is there any prep needs to be done before laying the ditra? I would note the ply is bare and to lift it to seal edges or anything else would be a mare!
Is there any need for expansion gaps? the heating is not underfloor.
and lastly what grout joint would you recommend? 2 or 3 mm ?

Thanks for any advise offered and if Ive missed out some info let me know

 

[J K Tiling Cornwall]

Plywood isn't the ideal surface to tile over but in your case it sounds solid and well seasoned. The main thing to remember is that it is pretty porus. I would use a SBR based primer and really wet it with a 1:3 coat (the 1 part being the primer). Then I would go 1:1. On the last timber floor I tiled (weyrock chipboard) I stuck the mat and tiled it all with an S2 adhesive. All good with no issues 👍

 

[humourme2]

Plywood isn't the ideal surface to tile over but in your case it sounds solid and well seasoned. The main thing to remember is that it is pretty porus. I would use a SBR based primer and really wet it with a 1:3 coat (the 1 part being the primer). Then I would go 1:1. On the last timber floor I tiled (weyrock chipboard) I stuck the mat and tiled it all with an S2 adhesive. All good with no issues 👍

Thank you, not the recommendation Id hoped for, but that is just because I have expended quite a bit of cash already. The ply that is down is very good quality, see image and as i said 25mm thick. I cant remember if its marine or wbp grade.
I bought the tiling materials quite a while ago and had seen so many references to AF200 i thought it was going to be ok. Do you think my plan would result in a failed install down the line?
The adhesive I have Keraquick is S1 and to use their latex mix to make it S2 would cost a lot more than buying an S2 adhesive.
If Im to go down the S2 route any recommendations?

 

[Ben-gee]

Ultra tile green bag is good.