Tiling onto a Timber/concrete kitchen-dining floor

[cp3147]

Hiya, i went to look at a job last night and its a 25 m2 kitchen floor to be tiled in 600x600 polished porcelain tiles, the floor is one half timber floor boards and the other half is concrete. It was tiled before but the customer says it had cracked and failed in both sides, when he ripped the old floor up on the timber side they had overplyd it and on the concrete part they had just tiled onto tiles to acheive the same level. I have recommened we use Schlüter-DITRA to over come the problem of the new floor failing, i was wondering if you would lay the matting straight over the timber-concrete substrate or wether you would recomend putting a thin screed over the whole floor before installing Schlüter-DITRA? and also would it be advisable to put a movement joint directley over where the timber floor changes to concrete? the kitchen/dining area is 8.5 linear metres the change in substrate is at 4.6 linear. Any advice would be greatly appreciated as i have never tiled a room like this. Thanks

[grumpygrouter]

The Ditra will not stop the timber side failing due to deflection. You will need to ensure the timber side is adequately braced first and then carry through to the tiling a movement joint.