To Overboard Or Not? - Tile Advice

[On one]

A have a flood damaged property to price some large format stone work for...........
Some of the rooms will be brand new timber joists and P5 chipboard. I will fit uncoupling membrane but,
can/should I go straight onto the P5 with the uncoupling membrane?
The book says yes fit the uncoupling membrane straight onto the P5(with s1,s2 adh or Ardex AF200),but sense says to overboard with cement boards.
A penny for your thoughts please......

PS before the flood this subfloor was timber flooring overlayed with 6mm ply,large format tiles and apparently no cracks/movement

 

[Flintstone]

I would definitely overboard it. I don't trust tiling onto any chipboard. I know a lot of people say uncouple with natural stone but if it's over boarded and its solid, I would tile straight onto the boards. Large format natural stone is often very thick

 

[White Room]

The P5 is the moisture green stuff, overboard...

 

[On one]

I got some info emailed over to me from Schluter and apparently Ditra will go straight on to P5 but.......you have to abrade the surface of the P5
Or straight on to P4 chipboard..........not too sure how widely available that is?
Overboarding would make me happier but I can see me being priced out on this one.

 

[Flintstone]

Over board of nothing. Why risk it. Imagine just tiling it and then getting the dreaded phone call in a few months.

 

[Flintstone]

Normally If you explain it to the customer properly they will be ok with it