Floating floors: compression vs vibration

[Workerbee]

Hello! I know floating floors have been discussed before, but I wanted to check my thinking with you guys before going ahead. 

I want to install natural stone and electric ufh on top of a floating floor in the kitchen and bathroom. Currently the buildup is concrete slab, then 50mm polystyrene, a vcl then 22mm t&g chipboard and carpet/stick-on vinyl tiles. Current ideas are: 

- 60mm ravatherm XPS, bonded to slab with approved adhesive, then 6mm insulated tile backer board. This would eliminate the floating floor as everything's bonded. XPS also has very high compressive strength; but does this also mean low vibration?

- 50mm PIR or phenolic, then 10mm insulated tile backer board. Again, I could bond this with pu adhesive; it's only being squashed, so the fact it's foil faced shouldn't matter?

- PIR/phenolic then insulated routed XPS boards for wet ufh pipework, then electric ufh mats above. I don't have gas, and heat pumps aren't currently suitable for my property, but this would give electric ufh now and the option for wet ufh should a suitable product come to market in the future. 

- if none of these is an improvement, then leave as is.

 

So it's basically xps Vs PIR/phenolic: very high compressive strength vs better insulation. But does compressive strength mean low vibration for fitting stone? Can PIR be adhesive bonded to the slab?

 

 

Thanks!

[Nickfromwales]

OK!!

 

Give us the depth you have to play with, from slab up to FFL please, as there's a lot of info but it's all a bit tricky to correlate.

 

And why electric UFH? It's the most expensive thing you can run, and is this for supplemental heating or full-on space heating?

[Gus Potter]

37 minutes ago, Nickfromwales said:

Give us the depth you have to play with, from slab up to FFL please, as there's a lot of info but it's all a bit tricky to correlate.

Agree with @Nickfromwales Is the floor separating two different dwellings? 

 

If you are adding load to the floor have you checked that is ok? 

 

A drawing would help a lot. You need to start with the basics and develop from there. You can maybe see it but for us it's difficult to comprehend as a complete floor design. If we can't understand it then little chance your builder will and the prices you get will reflect that.

[Workerbee]

Thank you for the replies, and sorry for my poor explanation! It's a bungalow, and in terms of compressive strength I think any of polystyrene, PIR or XPS should be fine. I've done a crude drawing of what's currently there:

 

 

The finish is currently carpet or tile. I'm basically just thinking of replacing the polystyrene with either PIR or XPS (ravatherm seems to have a decent lambda value), and replacing the chipboard with insulated tile backer board. This will mean I can bond everything together with suitable adhesive so that it's technically no longer floating, because the finish will be natural stone, which can obviously cause issues on a floating floor otherwise.

 

I wondered if the ravatherm might have two benefits over PIR: would the fact it's not foil faced mean it bonds better? And more importantly does the higher compressive strength equate to lower vibration, or is that a separate characteristic?

 

It's an all-electric house, so that's why I'm thinking of electric ufh. It'll probably be secondary heating, but given I'll be installing oil filled radiators it'll end up being just as expensive!

 

Thanks again.

Edited November 2 by Workerbee

[Workerbee]

Having spoken to a few technical departments, it sounds like compressive strength and 'vibration' (ie movement that could crack grout) are separate issues. Movement is caused by gaps due to each layer not being perfectly flat. Therefore I might as well use PIR/phenolic instead of XPS. Bonding the layers with pu foam will help with movement.

 

In terms of what to put on top of the PIR: I was thinking xps tile backer board, as it adds more insulation and high rigidity. However, one technical department thought this might not work as it's not tongue and groove. Are they right?

 

If so, and I need to use something with tongue and groove, is there anything offering better moisture resistance or thermal qualities than chipboard?

 

Thanks!

[JohnMo]

On 31/10/2025 at 22:09, Workerbee said:

heat pumps aren't currently suitable for my property,

What is the reasoning behind this statement.

 

From what you describe you are going to need a big pay check to pay the heating costs. I would step back, post some details about your house and ask for suggestions

 Your proposal is going to end up a very poor performer and super expensive to run.

 

Poor insulation in the floor (this is what you currently propose) when heating the floor is actually worse than no insulation in many situations.

 

My solution would be ASHP, remove current floor to the concrete, egg crate panels (no insulation) and then 16mm UFH pipe at appropriate centre spacing. Screed. Then your stone floor finish. But do over whole ground floor. If you don't want that, dump the whole UFH project. And do your proposed plan for electric UFH only in bathroom on a timer. Then install modern storage heaters on E7 or better Octopus storage heater tariff.

[Workerbee]

Thank you very much for this, @JohnMo Yes you're right, I've had concerns about cost, but I feel I'm trying to find a balance with different factors.

 

It's a bungalow, less than 50sqm. I'm adding 100-125mm PIR in the ceilings and 50mm on the walls. I'll be draft proofing and, although it'll never be ultra airtight, I'll add dmvhr instead of dmv. So hopefully it's a fairly small, fairly well insulated space to heat.

 

A heat pump would be nice, but I can't really afford the cost up front. It's also a very quiet location, and after visiting several heat pumps I didn't feel it would be suitable. Also, with the size of the house, I don't know where I'd fit the extra equipment. Even a uvc is a headache (but I want the better flow rate vs an electric shower)! I have no wet system - it's an all electric house.

 

The electric ufh is mainly just to take the chill off the floor, with a mind to it being used more in the future if I get batteries.  Kitchen is about 16sqm, bathroom 4sqm. I also considered adding pipework for wet ufh in the kitchen as well as an electric mat, so it's ready to use if a more suitable system came to market in the future. 

 

Storage heaters would be a better idea than oil filled radiators; however, I've never found any that look particularly nice, so I'm a bit stuck.

 

Thanks again

[JohnMo]

28 minutes ago, Workerbee said:

Storage heaters would be a better idea than oil filled radiators; however, I've never found any that look particularly nice

Just had a look about and Rointe Onyx HHR Storage Heater don't look bad

Stiebel Eltron SHS Storage Heaters - HHR but boxy but looks pretty clever.

 

You should only need a couple, bedrooms would just be panel heaters anyway

 

 

[Workerbee]

Thank you for finding these @JohnMo - I'll have a look.