Help!: Tile over two substrates

[Ric28]

Could someone help me please.
I am tiling on a floor with 30 x 30 x 12mm slate tiles around a breakfast bar which has recently been replaced by a new but smaller one leaving a gap of about 3/4 of a tile width between the bar and the existing tiles. Most of it is onto concrete (not a problem) but at the end of the bar the concrete meets floor boards and one tile is going to have to straddle the two substrates with 3/4 of it on the floor boards.
I was thinking of laying a piece of Ditra matting down and laying the tile on that but think the matting might raise the level too high to lay the tile level with the existing tiles.
Would this be the right thing to do if I used very thin layers of addy to try and get it as level as possible or is there a another way?
Thanks
Richard

[doug boardley]

that's a tough one Richard. You should use expansion joints where the two substrates meet. I think I'd remove the floor boards if possible and use 18mm wbp ply and a decoupler on the ply, but also try to make a feature out of it by using the expansion joint at the transition point.

[Ric28]

Sorry Doug - had to dash out earlier but thanks for your advice. I know what you say makes sense but I was hoping not to have to have a cut tile there as it will look odd next to a whole tile and a lot of hassle for one tile. But it might be the only way to have peace of mind.
Cheers