Electric Underfloor heating and SPC

[MikeGrahamT21]

So i went ahead and bought a 140W/m2 foil underfloor heating mat for the new bathroom im working on at the moment, thinking that was suitable to go under Stone Plastic Composite (a type of LVT) flooring. Floor construction is suspended timber, will 100mm insulation between joists, and a 10mm marmox board on top.

 

I wanted to ask about the method of laying the foil mat, and whether a further XPS layer would be required to get rid of the potentially hard surface of the marmox, and was told yes, XPS layer, then mat. However they then advised me that laying SPC on top of the foil mat wasn't advisable as it would end up showing tramlines of the heating cables through onto the surface over time, and recommended MDF below the SPC, until i made them aware it was a bathroom, they then said I need the sticky mesh mat and self leveller.

 

I'm more than happy to return and go with a sticky mat and self leveller, but i've also found other foil mats online and they seem to be saying that the above minus the MDF is absolutely fine for SPC flooring

 

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The mats are very easy to install, positioned ‘floating’ beneath the final floor. Importantly, the heating should never be laid directly onto a concrete or wood subfloor. Without the correct insulation installed, will drastically reduce the response time and void the warranty of the heating. It is important to consult the floor manufacturer, making sure it is compatible with a ‘floating’ heat system. Alternatively, the loose cable or mesh mats can be installed (embedded in a self levelling compound). The Foil mat is safe to be installed in Bathrooms and Wet Rooms when installed beneath Waterproof flooring. Under Laminate or Wood, our 6mm Impact Plus Insulation should be installed, before the Foil mats are laid. If looking to raise the floor height to accommodate thresholds, an additional layer of 6, 10, 20 or 30mm XPS Thermal Boards can be installed beneath the Impact Plus Insulation. Under rubber-backed lower profile click floors (like LVT/Vinyl/Amtico) only the XPS thermal boardsshould be installed.

 

When i asked where i bought it from, i'd already sent them an email but was impatient and went on live chat which is where the above came from about sticky mat, but have just received a reply to my email ...

Having asked:

Quote

Hi,

Laying this mat in bathroom, I've got 10mm marmox down on top of the chipboard, can this be laid onto the marmox directly or would it need another layer of thin XPS for protection? SPC LVT flooring going on top.

Cheers
Mike

 

Their reply was simply:

Quote

Good afternoon,

You will require a XPS layer over the marmox before the foil mat.

Many thanks,
Alex, customer services

 

So as you can probably guess i'm now rather confused. If i can help it i'd really rather not use self leveller just from a mess perspective mixing it all up.

What have others done with this type buildup? I did reply to the message and told them what i got from the live chat other day, awaiting reply.

[Alan Ambrose]

I've done 3 of these floors in kitchens / bathrooms so have some experience but not lots. Yeah, suggest 10mm insulation board (thicker if possible) and then 'self level' screed over the mat. You can also use simple heating cable instead of mat but ensure it's a shorter length than the max needed to you don't need to cut it - as the suppliers won't warranty it otherwise. Buy the best stuff you can find.

 

Other tips - ensure you can get at the connections reasonably easily and put in a spare thermistor in case the original one goes bad.

 

What controller will you use?

  

[MikeGrahamT21]

Had thought about and still considering using cable and a decoupling mat, but since it would still need self leveller I may as well go sticky mat if I can’t use this foil mat.

 

I’ve already got a thermostat, warmup 4ie which I’m currently using in the existing bathroom, existing and new will join together once completed.

[MikeGrahamT21]

They got in touch with their technical department, and yes I need the sticky mat embedded in 10mm of self leveller, in case anyone is wondering about the answer to this question...so a return it is