Engineered Oak Floor over anhydrite screed/UFH

[GrahameS]

I want some real-world BTDT advice.
The room planned is about 11mx6m with anhydrite screed and wet UFH
I think I want wide-board engineered oak
Questions:
Mostly I've read that screed moisture content needs to be <0.5%CM
Carbide method does not sound like diy task - who do I get to measure it?
Is there another way to know when the floor screed is dry enough?
I think I want to use Elastilon Strong - easy(ish), quick, good sound/vibration damping and good heat transfer
Do I need poly DPM under Elastilon - I read that poly rots with gypsum?
Or should I stick to fully glued? What does this need in terms of sealing the screed first?
I plan to lay the planks parallel to the longer room dimension
Is this OK?
Is there a way to size the perimeter expansion gap vs width?
Does this matter for length?
I'd be grateful for all advice - I don't want a v. expensive screw-up.

 

[WoodYouLike]

If you are going to use Elastilon, you have to opt for the "lock", not the strong. And you do need a DPM first (sheet or liquid)

Bonding with flexible adhesive is also possible - no DPM needed then, as long as the underfloor is dry - for instance Basicoll PU-650SE

How thick is your wood-engineered board and what is the mm of the top layer?
For measuring the mc, there are other moist meters around - see some of the hire centers.

Best to leave an expansion gap - all around, including where door posts are - of 10 - 13mm due to the 6 meter width of your room

 

[GrahameS]

From the Elastilon website - "Elastilon Strong can be used on under-floor heating in combination with solid wood or constructions." The Lock version does not sound like a diy job!
But I'm sure you're right about the DPM - half my project already has UFH + anhydrite screed and that was poured onto thick black poly over the insulation. It's been down a few months now and for riven slate covering eventually so moisture not an issue
It sounds like I need either patience or a moisture meter - apparently the ordinary resistance type won't do as it is a surface measurement. Where can I hire a Tramex CME? Google is not much help
The boards in mind are 220 x 20 with 6mm wear layer
The supplier recommends the Elastilon Strong.

 

[WoodYouLike]

Personally I would prefer a full bonding of the floor with a flexible adhesive such as Basicoll PU-650SE

Tramex is a known brand in the flooring industry, although our own equipment comes from a Dutch manufacturer Brookhuis

 

[JFJFlooring]

Elastilon Strong would be perfectly suitable for the job. Also a dead easy product to use with great acoustic values and heat transfer. Well worth the money and can often be cost effective because there is no need for expensive adhesives and also because of time saved in fitting.

If your screed has been down for a few months chances are it is probably dry. A good little test is to tape the edges of a polythene bag down to the floor and leave it there for a few days. If the bag condensates then chances are there is still damp in the screed. Not the most technical way, but an old fashioned method that does work