Underlay for Laminate floor using UFH

murphy31ie

Hi,
I have been looking into getting some underlay for the laminate floor I will be laying upstairs in a new build. The house is heated using UFH and I understand the lower the TOG value the better, it was mentioned that a layer of polythene should be laid first on top of the screed then the underlay the laminate. I was of the opinion that the dpc under the floor insulation and screed was the only polythene that needed to be laid. I am getting myself confused so any advice is most welcome.

This is the link for the underlay I was thinking of usinghttp://www.topline.ie/windows-doors-and-floors/flooring/timber-flooring-and-accessories/underlay/trojan-alufoil-silver-underlay-3mm

rampantbunny

murphy31ie wrote: »

Hi,
I have been looking into getting some underlay for the laminate floor I will be laying upstairs in a new build. The house is heated using UFH and I understand the lower the TOG value the better, it was mentioned that a layer of polythene should be laid first on top of the screed then the underlay the laminate. I was of the opinion that the dpc under the floor insulation and screed was the only polythene that needed to be laid. I am getting myself confused so any advice is most welcome.

This is the link for the underlay I was thinking of usinghttp://www.topline.ie/windows-doors-and-floors/flooring/timber-flooring-and-accessories/underlay/trojan-alufoil-silver-underlay-3mm

Can't help with the underlay question. I'll be looking for some myself in the future and from what I can see it is a minefield of choices.
Re. the layer of polythene, I believe that is to be laid over your insulation before your screed is poured on top. It is to protect the insulation from getting wet as far as I know.

murphy31ie

The guys who installed our Geothermal system said they didn't want polythene laid on top of the insulation, the screed was poured directly onto the underfloor pipes and insulation.

We went with the below underlay in the end up, hopefully it does the job.
http://murphylarkin.com/underfloor-heating-underlay-tog-0.35

rampantbunny

murphy31ie wrote: »

The guys who installed our Geothermal system said they didn't want polythene laid on top of the insulation, the screed was poured directly onto the underfloor pipes and insulation.

We went with the below underlay in the end up, hopefully it does the job.
http://murphylarkin.com/underfloor-heating-underlay-tog-0.35

Did you ask why they didn't want polythene murphy?
Was your floor insulation laid so that no screed would fall through cracks and touch your concrete slab/foundation and cause cold-bridging?

murphy31ie

There is a DPC layer underneath the floor insulation/on top of the slab.

rampantbunny

murphy31ie wrote: »

There is a DPC layer underneath the floor insulation/on top of the slab.

A DPM (Damp Proof Membrane) I think it's called as opposed to a DPC (Damp Proof Course) which is usually installed between courses of blockwork.
The DPM wouldn't effectively stop cold bridging. Some people go to the trouble of taping all the joints in the insulation boards before pouring screed. Not sure if I'll go that route myself.

Still would like to know why they didn't want polythene under the UFH. The UFH pipes could either be laid in special carriers (don't know the name) or pinned directly down to the insulation. If pinning, the layer of polythene would be punctured in any case.

murphy31ie

I am a total novice to all this so you are probably correct about the DPM, we mentioned taping joints but they said there was no need, just stagger the joint and ensure the boards are butted tightly.
I am not too sure what they used to hold down the underfloor pipes, it was a bracket is all I know.
My dad is a retired building contractor so he looks after everything, hence my lack of knowledge.

rampantbunny

murphy31ie wrote: »

I am a total novice to all this so you are probably correct about the DPM, we mentioned taping joints but they said there was no need, just stagger the joint and ensure the boards are butted tightly.
I am not too sure what they used to hold down the underfloor pipes, it was a bracket is all I know.
My dad is a retired building contractor so he looks after everything, hence my lack of knowledge.

Fair enough. You're lucky enough to have your father in the know at least.
Best of luck with the rest of it.