Rookery wrote:
I wouldnt put UFH directly onto any timber surface, the constant changes in temperature will cause movement and probably the tiles to crack/de-bond. I would fix min 18mm ply, screwed at max 300 c/s, then fix min 10mm insulation boards, then fix UFH cable, then cover in flexible levelling compound, then tile. The heating must be conditioned properly too. The more depth to the insulation, the better.
Would be my choice too
Just remember OP, don't be tempted to turn your heating on until after about 4 week, then when you do don't crank it up but start at about 15 degrees and increase by 1 degree every 24 hours, once you have reached maximum temp then you can decrease to the required temp