Wet Room Floor Advice Please

[EdinTiler]

I learn all the time in this great trade of ours and this is something I've never had to deal with before so I do totally appreciate all advice suggestions from all of you in whatever shape or form. I'm not scared of a bit of constructive criticism either. It's just that, as I'm sure you'll all understand, if it did go **** up then it's a 20yr friendship out the window and that's not something I particularly want.
EdinTiler

 

[J Sid]

My advice......DON'T do work for a friend who thinks he knows more about YOUR trade then you do.
It will end in tears

 

[Old Mod]

Make him read this thread!

 

[One Day]

@impish What would you suggest goes over the top of the plywood? I've only ever fitted the Schluter systems on raised plinths and platforms with the formed trays and membrane before. With no problems I might add. He'll be using ply regardless of what I say so anything that'll make my work as fool-proof as possible will be a consideration.
Thanks in advance
EdinTiler

Over ply? I'd use BAL Tank-it. BAL Technical say no, but I've done tests of my own - (for a terrace build up) and it stayed bonded and waterproof even after the wbp ply failed and delaminated.
No matter what you cover the ply with, be it a sheet membrane or liquid, it's just prone to absorbing any water it can get - even damp and condensation from underneath.
If the shower is used more than once a day, I'd guess it won't last more than 5 years - and that's if you make everything watertight from above.

 

[EdinTiler]

Thank you. So what would you use for the sub-floor if not ply?
Just spoke to my mate, expressed my dissatisfaction at nor wanting to listen to me and now he is prepared to listen. Thank god.
EdinTiler

 

[One Day]

At 2.2m length I would let him have his ply and even create the fall with it.
If it's all well supported and deflection free then get the best quality ply he can. BAL SBR to backs and sides to prevent moisture ingress, then for me - 12.5 mm Kerdi or Wedi board bonded and screwed down.
Ideally - Kerdi to a kerdi drain but if not, just tape and waterproof all fixings, joints and corners.

 

[EdinTiler]

Again, thank you very much for your patience with me and my stress levels. That's a big help. I will let you all know how I get on.
I'm off to watch This is England '90.
See you all tomorrow
EdinTiler

 

[One Day]

Don't sweat it. Just don't ever apologise to the other trades for wanting to do your job right!

 

[p4ulo]

I would lay on top of the ply with a wedi or schluter board or similar "waterproof" board, all joints glued, taped and stuck down with Kerdi Coll adhesive, then a layer of Schluter Kerdi over the whole lot....Best to build it to last. The pre-formed Kerdi corners are excellent for total piece of mind.