Tiling over two different substrates

[snapfish]

i want to tile the kitchen floor which has been knocked through. Half the floor is concrete and half is 25mm ply straight onto joists. I’m not too keen on the visible expansion strip on the floor.
The tile shop are use recommended putting a strip of ditra decoupling membrane each side of the joint, and say everyone does this. The tiles are large format 600*600 porcelain, and I’m going the line up the grout line with the crack, so if anything cracks it’s going to be the grout.
I can’t see how put ditra each side is going to take up the movement of expansion, surely the next tile along which is not on the Matting is going to grip onto the subfloor and stop any side movement.
Does this method work or do I have to lay the Matt on the whole floor or is there another way I haven’t mentioned?

 

[bobasd]

where both surfaces meet at the "crack" do they form a perfectly level surface?





Laticrete Strata matting will work over 3mm cracks but Laticrete want you to cover the whole of both floors in Strata matting not just over the crack.

tiling through a breakthro opening usually means a meeting strip of some kind, and if the surfaces are not level a transition strip is a necessity.

search on here and read the masses of Related Threads below.

 

[snapfish]

Yes both subfloors are level with each other. I’ve bit the bullet and layed the whole of the floor in ditra matting.
Now over the expansion joint, if you were doing the job, would you lay a row of tiles (600*600) Straight over the joint or butt them up to it? Last thing a want is a row of cracked tiles.