Flooring choice and install method for large area with UFH and sun exposure

I have an open-plan downstairs and will be putting in big bifolds (pretty much south facing). We're putting in wet UFH. Want to avoid porcelain since we don't like the hard feel and would like to avoid expansion gaps if possible (even with decoupling membrane it's too large an area). I'm torn between Impervia and glue-down LVT and, if glue-down, not sure best adhesive. I don't think I'll be able to get house warm enough with flooring at only 27 deg C - expect to need 30.

Impervia
- Love that you can run it at any temperature!
- Click lay is simple - but suspect you have to lift the whole floor (take skirting boards up etc.) if you damage a tile in the middle and need to replace. Is that true? (wondering if you could cut round the damaged tile to get it out and then glue down the replacement - but suspect you'd then get problems with gaps)
- Not sure how UV stable it is?
- Need for expansion gaps not ideal
- It's a retrofit and can't tear out the kitchen. For most of it can just go underneath the kickboards a bit but at the cabinet ends the flooring would need to butt up hard against the cabinet. Not sure if that's going to cause problems with gaps. Any recommendations?
- @merit I saw that you fitted it in a conservatory in early 2022. Would love to hear if that's all looking good still?

Glued LVT
- All the manufacturers say don't run your UFH above 27deg C and quite a few mention avoid direct sunlight. But... I have a glue-down LVT in kitchen and south-facing conservatory that's been in for 10 years with UFH running at 30 deg C (even with laundry or blankets sat on it when it gets really hot) and it's pretty much fine. Some small gaps which could perhaps have been avoided with better adhesive. So I'm thinking that maybe LVT is fine in a place with UV and high temperatures if it's on a good substrate with good adhesive?
- Cheaper than Impervia (although maybe not after factoring in adhesive and labour costs for fitting)
- Have read good things about Polyflor (assuming going for something like their Expona range with 0.5 - 0.7mm wear layer). Do they hold up well to UV? Amtico too expensive. Heard recent problems with getting Karndean to stick. Any other good brands to consider (0.5mm wear layer + bevels)?

Adhesive options
- PS: Assume I should avoid this
- Wet bed (e.g. Uzin KE66 or KE49HT): Sounds pretty good - but maybe not strong enough to stop shrinkage? @dazlight I saw you had a conservatory with KE66, was that south facing and getting super hot in the summer? If so - did it hold up well or any issues with shrinkage/lifting?
- Epoxy: Seems almost too strong. Can't imagine it getting affected by heat or ever coming unstuck but would think it's so strong that you'd never be able to replace a damaged tile without doing something extreme like setting up a router jig to cut out the old tile and glue? Also - seems like VOCs would be bad and very nasty install job?
- Silane (e.g. Murexin MS-K 499): Assuming this is pretty much the same stuff as Sikaflex. So extremely strong and a total bear to remove (in case of replacing a tile) but not quite as awkward as epoxy to remove (or install)?

Installation
- Installation instructions always seem to say that temperature must be between 18 and 27 deg C and UFH must be turned off (for 48hrs). I was hoping to install in late autumn / early winter so if the heating is off then it would definitely not be above 18 deg C so...
...wondering if it would be okay to have UFH turned on but just set it to a max floor temp of ~24 deg C which ought to just about keep room temp above 18 and obviously below the 27. Would that work or too risky? If it's too risky - how the heck does anyone do an install with UFH outside of a couple of May/June and August/September (+avoiding heatwaves)?


Sorry for the laundry list of questions! Any help on any of the points above would be much appreciated.
Thanks,
Tim

 

Just put radiators in

 

Ha! And brick up the bifolds, right! I'm not quite there yet...

 

Just blinds will help lol

 

Impervia is fine with heat and UV. It won’t change colour or expand as long as you have expansion. You will need to remove skirting or have some form of beading. Kitchens can be undercut. The floor will need to be very flat as it’s a top lock system. Board replacement isn’t a issue if you know how.
Stick down LVT could work too. Amtico HT extra adhesive is ok to use in high temp areas. And if they’ve put the uv protection in it won’t change colour too much.
Unfortunately it appears LVT manufacturers sometimes miss out the uv protection. So sometimes they turn green and sometimes they don’t! The better companies will replace it if it’s defective. You can get silane adhesives that will work in those temperatures and not as messy as epoxy.

 

We use F48 plus adhesive now. Go in wet and roll in with a heavy roller. Works for us. My kitchen diner is in ke66 and no problems with it.

 

And yes the Impervia in that conservatory is perfect. It’s insanely hot in there too. SW facing and glass all over. The Amtico spacia had totally changed colour and shrunk as it was laid on f46.
Be aware of cheaper spc clic products. We used one in the same conservatory first and it bubbled up. Wasn’t up to the job.

 

Thank you very much for the quick and detailed replies!

Appreciate that floor needs to be SR2 for Impervia - just spoken to a screed guy that is comfortable with that. Good to know about board replacement. Although interestingly, I spoke to Impervia and they claim that, having the stone based backer, it doesn't expand or contract at all so you can lay it right up to skirting boards/kitchen cabinets which sound ideal. Unless anyone has real-world experience that says otherwise?

I'm leaning pretty heavily towards Impervia (pending a quote!) but good to hear that LVT can work reliably in very hot places with KE66 / Amtico HT / or F48plus. Will definitely avoid SPC clic. Does sound like a bit of a gamble on knowing how good the UV protection is on LVT though since I would have thought a brand like Amtico would have been a safe bet but @merit's story about the Amtico Spacia changing colour is concerning.

Thanks again @merit and @dazlight!
Tim

 

I would say you still need some sort of expansion gap with Impervia as it’s a floated floor. It’s also very hard to clic in without a gap to work with.

 

Hmm, that does sounds sensible. Just saw a couple of videos on the tube about replacing a damaged board so feeling a bit more comfortable about going under the skirting now.

Thanks,
Tim