Wall prep question - Tile Advice

[Sacredhart]

Hi
been browsing the forum, lots of good advice. I’m after some myself of you don’t mind.

retiling my bathroom. Just the bath area so three walls 1700x 1700, 1700x700 and 1700x700. Taken off the old tiles and plasterboard. It’s stud walls with timbers at 600mm.

I have some 12.5mm wedi style boards to fit. I have read the wedi guide but it doesn’t mention ply over stud walls.
I have to fit ply over 2 of the walls as I have things to fix to them so I was planning to ply over all the stud work first with 12mm ply and then Fix the tile boards to the ply with tile adhesive and then screw through the tile boards into the stud wall.
Havent chosen tiles yet but they won’t be anything thick or heavy.

My questions are:
is having ply behind the tile backer board a problem?
if not is 12mm ply ok or should I use 18mm?
i was going to glue the backer boards together, Is A polymer adhesive/sealant oK for this?
should I screw through the backer boards whilst the adhesive is still wet or let it dry first?
should I use tile adhesive to stick the backer board to the ply or use the polymer adhesive?
i was going to use backer board scrim style tape over the joints and screws, can I use my tile adhesive to bed this and if so should this dry before tiling or be fitted as I tile?
anything else to consider?

thankyou really appreciate it?

 

[J K Tiling Cornwall]

No problems fitting the tile boards over the plywood (no different to preparing a floor) 12mm would be fine, prime the plywood first and bed the boards on with a thin bed of adhesive. Use the washer fixings with the screws, I do all at the same time and fibreglass tape the joints as I go 👍

 

[Sacredhart]

No problems fitting the tile boards over the plywood (no different to preparing a floor) 12mm would be fine, prime the plywood first and bed the boards on with a thin bed of adhesive. Use the washer fixings with the screws, I do all at the same time and fibreglass tape the joints as I go 👍

thanks JK!
appreciate you replying.

what are you priming the ply with?
are you using a cement based or ready mixed adhesive to bed in the boards?

cheers

 

[J K Tiling Cornwall]

Sorry for late reply...I use a dilute SBR primer and always a cement-based adhesive. Use standard set to give yourself more time. Glad to help

 

[Sacredhart]

@J K Tiling Cornwall thankyou very much. I really appreciate you taking the time! All the best.