Chevron Floor

[goz]

hi guys, went to look at a floor today, 35m2 of chevron planks. Great I thought... Can't wait.... Oh hold on a minute..... Two different substrates! Suspended floor on one half and screed other half! The joint is staggered aswell! Spoke to builder who just wants to put 20mm thick polystyrene board down to accommodate his wet ufh then have me laytex over top, just wants to bridge the two subs with it, thinks it will be enough!!
Any way round this? Bearing in mind it's chevron tile and joint is staggered.
Will it fail if he proceeds like this?

 

[Time's Ran Out]

Yes!

 

[hmtiling]

View: https://www.youtube.com/watch?v=sKbP-M8vVtw

 

[goz]

Haha great sketch!! Any way round it?

 

[hmtiling]

Sorry mate. Not very helpful. Not an obvious solution I can see.

 

[Stef]

Need to honour the expansion between the 2 substrates.
It will fail..

 

[J Sid]

controversial I know, but I would have made the suspended floor as movement free as possible with brick pillars or wooden supposes then glued the polystyrene boards 22mm down bridging the joint in the sub floor and Ditra over the lot before tiling.
emailed the supplies of these retro fit ufh boards to get there recommendation and the came back with the same as I was thinking without me giving them my thoughts on it.
I have used these board many time and are quite soft compared to other so can accommodate some movement.

 

[Flintstone]

I've tiled over mixed substrates a few times without putting in an expansion joint and to my knowledge it's been fine.