Large shower tray spanning UFH

[Kelvin]

I have a large 2000mm x 900mm stone shower tray ready to be fitted. However it’s going to span across a section of screed that doesn’t have UFH pipes beneath it and a section that does. Therefore there will be a difference in floor temperature from one end to the other. Is this a concern and should I mitigate by decoupling it or can we just bed it in a sand/cement layer as normal? 
 

Edited March 26, 2024 by Kelvin

[Nickfromwales]

If the shower spray hits the 'cold' end, then I'd just leave it alone. I'd not want a SR tray which is part bedded and part decoupled imo, due to risk of cracking over time.

[Nickfromwales]

Interesting place to have the safe btw....  

[Kelvin]

11 minutes ago, Nickfromwales said:

Interesting place to have the safe btw....  

😂 Because I don’t have a clue what I’m doing half the time I left myself some wiggle room! 
 

Yes the shower spray will hit the cold end so I should just bed it across its full length from the cold bit to the warmer bit. 
 

 

Edited March 26, 2024 by Kelvin

[Kelvin]

It’s a Sommer shower tray. They are recommending I don’t fit the tray at all! Balls. They may be being over cautious of course. My reason for considering decoupling it was similar to why some people recommend setting the sand/cement screed to some plastic sheeting to decouple it from a wooden floor. Now uncertain what to do.
 

The instructions also say it just sits on a bed of Sikaflex.  
 

 

Edited March 26, 2024 by Kelvin

[Alan Ambrose]

I'm seeing "Material - Stone/Stone Resin"?

 

I would just fit it, that's what the flex is for in Sikaflex.

 

Sure, you could do some 3D heat flow calcs, some differential expansion calcs, and check the expansion allowances for the mastic etc ... but ... my guess is that the temperature would equalise fairy well / the differential expansion would be minimal for 'stone' vs. your (screeded?) floor / the mastic would absorb that expansion.

 

Does anyone actually do any calcs or tests for any mastic joint unless you're, say, an EWI system designer or industrial plant designer?

[Kelvin]

The dark grey stuff is is a self levelling compound (Arditex NA) which was the infill for the shower area. It has the same insulation underneath it as the rest of the floor but no UFH. The light grey is Cemfloor that has UFH within it. The shower tray is a stone/resin shower tray. 
 

 

[Alan Ambrose]

Well the numbers are probably not published anywhere for those products, but they will have similar-ish thermal expansion coefficients as they're all some kind of stone-like powder with a binder.

 

That is, we're not looking at something like glass bonded to steel at one end and stone at the other. 

 

So, I think, along with the flex, you're good

 

[Kelvin]

Well it’s in! Will have to move that socket. 

 

[Nickfromwales]

23 minutes ago, Kelvin said:

Will have to move that socket

@Russell griffiths will buy it off you to put into his shower. 
 

https://uk.manscaped.com/?gad_source=1&gclid=CjwKCAjwh4-wBhB3EiwAeJsppLhk7T6msHWJqwLDERuPaiTVuQ-HMwEBW3lkxisRmdQsqURDwOqvFxoCiLEQAvD_BwE

[Nickfromwales]

Is it in and bonded now? Did you seal at the perimeter? 
 

I don’t see you ever having a problem btw, and the Sika stuff is very good. 

[Kelvin]

Yep. All sealed. Will be tanked and I have the no more leaks kit to fit too. 

[Russell griffiths]

2 hours ago, Nickfromwales said:

@Russell griffiths will buy it off you to put into his shower. 
 

https://uk.manscaped.com/?gad_source=1&gclid=CjwKCAjwh4-wBhB3EiwAeJsppLhk7T6msHWJqwLDERuPaiTVuQ-HMwEBW3lkxisRmdQsqURDwOqvFxoCiLEQAvD_BwE

Handy for when I do my legs.