Engineered floorboards on screed for wet underfloor heating

[Peterade]

I'm having wet underfloor heating installed. After the screed is applied, how do you fit engineered floorboards onto the screed?

Obviously you can't nail. If you glue it wouldn't it warp?

Thanks to anyone who knows,

Peter

 

[mointainwalker]

Glues are tremenously powerful these days ( should be given the huge prices!! ) and you want the best possible "connection" to maximise the heat transfer from the screed.

Uses
For bonding of solid and engineered flooring to strong, sound dry substrates. High strength. Bonds all woods including parquet, wood block and wood strip. Suitable for use with warm water underfloor heating systems

Above quote from the Laybond ( Bostik) site. You need to make sure your screed has thoroughly dried out before glueing.


Is it self-levelling or cement/sand screed ?

As far as warping goes, I haven't ever seen any complaints about that on here being attributed to glue.

 

[WoodYouLike]

And don't forget to follow the specific start up steps for your UFH before you start the installation of the wood-engineered floor.
Half way down this page you can find a guide what to do before, during and after installation on UFH

 

[Peterade]

Thanks,

It's self leveling Anhydrite screed.
I was worried that if you glue it down, the screed may expand differently & the wood would warp.

Thanks for tips.

Peter

 

[mointainwalker]

That's why they recommend a flexbile glue but this stuff costs about GBP 6 per kilo which only covers 1/1.5 m2 !!

Edit

I did talk to someone from Bostik Technical and although they specifically say on their site that their rigid glues are OK for UFH, after a lot of me pressuring him to explain why he was recommending the flexible glue when the rigid was OK, he finally said that the rigid was capable of tearing up the screed in the start-up/cool-down phases.

 

[Peterade]

Heating Engineer has just re-visited & said best results will come from a floating floor and the benefits of heat transmission from gluing are negligible considering the always on nature of UF Heating.

Thanks for all your points,

Peter

 

[mointainwalker]

Irrespective of any other points or views, your engineer is simply wrong when he says

best results will come from a floating floor

Logic will tell you that floating means there is a layer of air and air is quite a good insulator when talking about small gaps.

I also don't think ( not certain ) that you can simply lay it on the floor: it is usual to have an underlay which means further insualtion.

 

[WoodYouLike]

I second that. Most manufacturers of wood-engineered floors will recommend you fully bond the wood with flexible adhesive when there's underfloor heating involved to avoid air gaps.

 

[Peterade]

Can I ask, would the engineered wood be glued to the self leveling Anhydrite screed or would you have to lay a board to the screed first?

 

[mointainwalker]

Engineered-wood direct to screed, no intermediate.