Floating Chipboard Floor over Hetta wet ufh pipes (like polypipe)

[aflemi]

Tx input guys. Mapei came back, wouldn't guarantee at all but said best method was their ditra equivalent and keraquick with latex+. Called Bal and the guy nearly had a heart attack, wouldn't tile it. Chalker, spoke to these guys
http://www.jupiterunderfloorheating.com/fermacell.php
who were very helpful. They said the fermacell boards over their heat boards would be ok for tiles up to 400sq but over that size they recommend their Screed Replacement Tiles which are on their website, 20mm deep, (its on their website) which are cemented together and they will GUARANTEE NO FAILURE when their 30mm heat boards are used.(I did some digging and their heat boards have kPa value of 240 compared to Hetta's 100 so basically are 2.4 times more dense and rigid. I can install these boards in the bigger room, get the builders to feed the cable through them instead of the spongy ones and use the Screed Replacement Tiles which gives me much more comfort.
Not sure what to do with other room, ufh and chipboard is already done. Anyone know of a very good engineered wood (ish) product? May still ditra and tile as only guest bathroom, no bath and everything wall mounted....
The Jupiter heating guys really know their stuff, in stark contrast to Hetta who said this today

[FONT=&quot]When the pipe is in the panel it also adds a lot of strength, especially as the pipe is spaced at 150mm centres[/FONT]
[FONT=&quot]As long as flexible adhesive is used with tiles, and a the plywood has a 10mm ga left around the perimeter to allow for any slight expansion etc[/FONT]
[FONT=&quot]There shouldn’t be any issues at all[/FONT]

 

[aflemi]

Screed Replacement Tiles dets...........
http://www.jupiterunderfloorheating.com/srt.php

 

[Joy2019]

Yes, its for apartments building regs. In theory I could remove top chipboard layer, replace with 18mm ply marking location of pipes and screwing down to bottom chipboard layer with hundreds of screws. One room is 4x3.3m and plan bath at one end so with weight difference full/empty of +350kg it needs a good base that wont flex every time bath filled/emptied. Have called Mapei and they were sceptical on phone but are reverting by email. Anyone have experience of polypipe install covered with floating layer?

Any ply or similar wood is not acceptable for tile installation under british standards, should be overlayed with suitable tile backer board.