Part timber, part screed floor with some underfloor heating. Help!

[LoafJaw]

Hi all,

I have been asked to lay a downstairs floor seamlessly (no breaks, threshold trims etc). The problem is that the main area is floorboards/ply which then flows into a new conservatory which will be new screed and underfloor heating. Obviously the difference in expansion qualities is getting me a bit nervous as far as no expansion joints or threshold trims is concerned. Can it be done? Would Ditra be enough or would you insist on some sort of expansion trim where the ply area meets the screed/underfloor heating area?

The tiles are wood effect porcelain, 96 x 24 cm.

I have emailed Ardex and Tiletrim technical help desks but had no reply from either. Please help!

 

[White Room]

How thick is the ply fixed to the floor...

 

[Time's Ran Out]

You must follow the structural break through to the surface of the tiles, so an expansion joint must be used!
Try and get the planking to run either side of this joint and it may not be so obvious.
I'd still then consider both side independantly incorporating the uncoupling membrane in the method of tile fixing.

 

[Rich Midge]

The way I do these floors is as follows. Overlay the floorboards with ply carrying it over onto the concrete by a good half metre or more. Glue and screw ply into concrete. Obviously make sure your floorboards are sound to start with, strengthen as necessary. SLC concrete to level with new ply. Ditra or Dural the whole floor. Yes, expansion joints should always be used but this is the method I've used for years with customers who just won't except expansion joints.