Laying TLC Vinyl planks over chipboard and underfloor heatin

[JJayy]

Can anyone help me? I have TLC Treu Forest vinyl planks to lay in an unptairs bedroom. The floor construction is 22mm flooring grade chipboard over underfloor heating (it is Wunda wet underfloor heating between joists - with the aluminium spreader plates over).
I have been advised to lay 4mm or 6mm plywood over the 22mm chipboard before laying the vinyl. Is this really necessary? I would have thought any slight unevenness (joins in the chipboard etc) would be smoothed out by the adhesive. Not quite sure why I'd lay plywood over the chipboard, as it would have to be screwed / nailed down, surely this wouldnt heap with any expansion / contraction issues anyway, and would just further increase the response time of the underfloor heating?
Any advice appreciated.
Also, advice on adhesive appreciated? - is F-ball what I should use, or is there a better or cheaper alternative?
Thanks.

 

[lymmranger]

Yes you MUST ply first and 6mm not 4mm

 

[JJayy]

Thanks for the reply. Could you explain why?

 

[lymmranger]

The manufacturer specifies either 6mm ply (on wooden sub-floor) or suitable screed on concrete sub floor.

In any case chipboard is definitely NOT suitable

 

[JJayy]

Thanks. I cannot find the manufacturers specifications online.

 

[crazydaze]

Thanks. I cannot find the manufacturers specifications online.

It does'nt matter. as Lymmranger has said, it's standard regs to bond flooring products to ply at least 6mm thick. Yes the ply evens the floor, but more importantly, it is a far more stable product than chipboard which will not be suitable for the adhesive to stick to for a number of reasons, but long story short, the tiles will warp,lift and generally fail if bonded to the chipboard directly.

 

[dazlight]

Do alot of tlc, big seller due to the low price.
Plywood the chipboard then feather finish screed to joints.
Adhesive you can use is F44 or F46