Mind you, for a 60sqm bedroom wing, I'm looking at about £1.2k for the styrofloor thing, or as little as £800 if I buy xps and chipboard separately... Appreciate this is not comparable to 10cm PIR, but will probably feel better than 2mm LVT glued to concrete. I imagine at the rate we're going, this time next year we'll be paying £800 for a tank of diesel.

Biggest issue is the 4-6cm reduction in door height.

Edited yesterday at 08:441 day by tetris

18 minutes ago, tetris said:

carpets in a corridor won't survive a fortnight.

You do have to pay more for hard-wearing, which will last years.

If you don't mind the utility look then carpet tiles . In office quality they will last you out, and allow kids' wheely toys, and for any accidents, plasticine or damage, can be taken outside to clean.

I have some salvaged from an office after 7 years of heavy use, used in a corridor, gym, workshop area. It is on an uninsulated concrete slab. I put an underlay of 10mm down first. The theoretical insulation (by U value) is low but much better than nothing, and the effect on feet comfort and warmth is significant.

Not sure this really makes sense in your situation but throwing it out there just in case:

If you are thinking about putting thin polystyrene in the floor and boarding over it, then think about whether you could use one of the thin UFH products (pregrooved polystyrene that acts as a template for the pipes). That might solve your radiator issues (and generally UFH will be cheaper than buying a load of vertical rads).

Important note is that the insulation layer is not thick enough for an external floor (would be very expensive to run), but if all you have below the floor is another habitable room then the small amount of insulation might not be a big deal. It would certainly solve the cold feet issue.

The floor still won't be as good as a screeded ufh setup but everything is a compromise.

The biggest issue in your case @tetris is likely that you want to do this quickly while living in the place and doing that with the floor might be tricky and certainly requires careful thought.

Thank you - it's a bungalow, and I've read (on this forum if memory serves me right) that unless you have 10cm PIR below UFH, all you're doing is heating up the floor void.

Just now, tetris said:

Thank you - it's a bungalow, and I've read (on this forum if memory serves me right) that unless you have 10cm PIR below UFH, all you're doing is heating up the floor void.

Doh! You are correct. Sorry I think you mentioned that in a previous post. I was thinking this was a first floor.

Edited yesterday at 10:071 day by -rick-

I would spend time making sure your floor is sealed to stop drafts that may be there. Then spend you money a good thermal underlay and a wool carpet. Do the same in bedrooms and corridor.

A very quick search brought up this

https://www.carpet-underlay-shop.co.uk/collections/thermal-insulation-underlay/products/56oz-heat-insulation-wool-carpet-underlay

15mm thick, add a good carpet job done.

Sealing the floor to make sure it's airtight would be my priority.

Another layer could be thermal tile backer boards, glued direct to floor and then underlay and carpet.

Thanks.

SWMBO sets the cleanliness standards around here, as she's the one who does the cleaning. Her view is that carpets become very dirty to the point of needing replaced the moment they leave the manufacturing facility 😁.

Carpets in bedrooms might just be the way to go in our case, but no carpet is ever going into the corridor (and I have to agree - the amount of dirt that my kids will get into it within the first fortnight will make me want to chuck it out). Even for bedrooms the carpets would not be our first option. Small kids get sick all the time. When they get sick, they puke. If that gets into the carpet, even a weekend with a carpet cleaner is not going to get the smell out of it.

Here's a thought: Would 25mm XPS sheeting take care of slightly uneven flooring (within +/-2mm perhaps?), so I can just put 18mm chipboard on top and that's the top floor ready for clicking? Sounds like a huge time saver if that's the case.

Current carpet + underlay thickness in rooms is 15mm. If I raise the floor by 50mm, less 15 from carpet removal, less another 15 from raising the doors, I'm only getting a net floor height increase of 20mm. If that means fast & easy floor installation + some insulation benefits, this is starting to look quite attractive.

In that case go straight tile backer, even a couple of layers glued down and tiles. Why bother with the chipboard at all

chipboard to spread the load of the click flooring?

Tile backers description reads like they might be OK but has anyone here used them for flooring?

2 hours ago, tetris said:

has anyone here used them for flooring?

yes. under a heating mat under tiles. and it's no bother. they are a good compromise of insulation, strength and general robustness.

If I understand correctly, it's just XPS with a thin hard layer on top of it?

I'll be floating click laminate or LVT, rather than gluing tiles to it, and none of these are officially compatible with click flooring because it spreads the load differently from glued-on ceramic tiles?

And does the XPS act as a DPM in itself?

Apologies, I might be asking very daft things here.