Large kitchen/ diner and utility room (40 sq m). Part suspended (chipboard) floor, part new concrete screed - both at same level. 450mm floor tiles to be laid throughout. Looking for an alternative to fixing plywood before laying tiles, preferably as thin as possible but with high compressive strength. There is a very heavy table which will be in the area with the new screed. Any widom appreciated.

On your head be it !

Your direction should be overboard the whole area with 12mm ply then Durabase CI uncoupling membrane before tiles.

Compressive strength doesn't come in to it your working with point loading on a 450mm tile.

tiler

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Welcome to the forums Stephen! If you want to keep the thickness down you could try using one of the backer boards like nomoreply and then overlay with a decoupling membrane

Kev

.......and make sure you have an expansion joint where the timber/concrete meet.