Wet Room Advice Please!

[Lakey]

Evening all,
I have a wetroom install & tile coming up which we have done before however it was some years back.
It is 1st floor extension so in effect a new build.
The small wetroom is currently studded out ready to receive boarding.
Apparently the plumber has installed an Impey shower tray on 18mm marine ply.
I am just looking for confirmation on the correct process after that.
The tray is 22mm and the ply obviously 18mm making 40mm which we have to build up to.
I initially wanted to lay 18mm onto joists followed by 10mm Dukka board and a UFH mat with screed at 3-5mm.
Obviously that only equates to 33mm max.
So my questions are
a) When do I tape the Dukka to the tray
b)Should I make up the level with a thicker screed or additional ply on top of the 18mm marine?

Any help would be greatly appreciated.

 

[Dave]

Is it an impey GRP tray ?

 

[Lakey]

Alright @Dave, do you mean the plastic ones as opposed to the foam core ones. Not sure mate haven't seen the job yet and won't be until tomorrow am.
What are the implications on one compared to the other?

 

[Dave]

Alright @Dave, do you mean the plastic ones as opposed to the foam core ones. Not sure mate haven't seen the job yet and won't be until tomorrow am.
What are the implications on one compared to the other?

If its the GRP , then spanning a 450mm joists isnt normally a problem .. Its the height build up hes created thats a pain .. Even if it was the polycore tray , then you line in between the joists with ply for support and not overlay , which increases the height..

 

[Lakey]

Yeah I see what you mean.
What would be an ideal set up if it's a polycore tray which I'm going o take a punt and say it is as I don't understand when the SLC comes in?

 

[Dave]

Yeah I see what you mean.
What would be an ideal set up if it's a polycore tray which I'm going o take a punt and say it is as I don't understand when the SLC comes in?

This might help for a polycore type tray..


View: http://youtu.be/QVMgP9C9FFw

 

[Lakey]

Cheers @Dave completely makes sense and actually think I've seen this one before.
What this doesn't show however is what to do if you want an UFH mat on top of the 10mm board. Usually I would put SLC over the top of the mat but surely this would affect the heights in relation to the tray?

 

[Dave]

Cheers @Dave completely makes sense and actually think I've seen this one before.
What this doesn't show however is what to do if you want an UFH mat on top of the 10mm board. Usually I would put SLC over the top of the mat but surely this would affect the heights in relation to the tray?

The tray should be installed to allow overboard and the wire thickness plus slc ...

 

[Lakey]

That's what I was assuming.
So eg the tray would be 5mm above the surrounding boards but still taped?
Then the UFH mat installed with a creed to bring it to the level of the tray....yes?

 

[Lakey]

*screed

 

[Dave]

That's what I was assuming.
So eg the tray would be 5mm above the surrounding boards but still taped?
Then the UFH mat installed with a creed to bring it to the level of the tray....yes?

Then you can tank over the whole lot ...

 

[Lakey]

Ok loud and clear @Dave
Thanks for your help