What type of underlayment should be used when installing engineered wood over underfloor heating

Question

I have recently purchased an engineered wood floor and wish to install this over underfloor heating (A Nu-Heat water based solution which sits between the joists). The joists are currently covered with a thin layer of plywood and my plan is to install on top of this. I have been advised not to float the floor but cannot find a suitable underlay alternative to use.

I have spotted the Elastilon Lock product as a double sided adhesive underlay allowing me to fully bond the floor to the plywood layer - but its website description suggests it only allows for minimal tolerances (presumably in expansion/contraction) and is aimed at parquet style floors.

Would this be suitable for a standard plank engineered wood flooring, or could you suggest an alternative?

For reference the floor I have purchased is

https://www.discountflooringdepot.co.uk/gold-series-engineered-flooring-walnut-18-4mm-x-150mm-uv-lacquered-1-65m2-p457

And Elastilon Lock website:

http://www.elastilon.com/en/elastilon/elastilon-lock

Answer 1

I don't know why you would've been advised to glue or lock a floating floor down. This a very bad idea & could make the floor cup or ridge if the floor can't move. Parquet is very different in being extremely small pieces with extremely small omnidirectional movement in a whole lot of very small areas.

Having no underlayment is the typical way & allows any moisture from condensation to escape, radiant floor's secondary activity. Foremost, is abiding by the Flooring Manufacturer's written instructions & approvals (over the phone means nothing) above & beyond whatever I or anyone else tells you. Do what the Warrantor says & even file pictures away to back up your by-the-book professional installation.