Insulating a solid floor?

SWMBO

We have a 1950s built house with solid floors, currently with parquet down, but the blackjack waterproofing underneath has failed so it all needs to be taken up. We've asked about improving the thermal insulation at the same time, but the flooring contractors we've spoken to only have experience with acoustic insulation under LVT.  Can we use thermal insulation under LVT? How do we find a contractor who knows what they're doing with it? We've already tried asking around family & friends, but to be honest they're not that bothered about insulation. (Maybe that will change as they start getting giant fuel bills?!)

Bendy_House

When you say 'it all needs taking up', what do you mean? Just the thin dampproofing coating, or the whole concrete floor so a proper DPM is laid first?

If the former, then you can only add insulation on top, so I'd suggest you work out just how much you can add. How far can you 'raise' the floor height without causing an issue?! Doors can be trimmed slightly, but you need to avoid a trip hazard at the doorway.

If the whole floor is coming up, then proper insulation should be incorporated in the new slab. I can't imagine for a second that a builder would be entertaining replacing the slab without adding the current regs of insulation, so I suspect that all they'll be doing it laying a new liquid DPM over the existing. Can you confirm?

So, you might only have the thickness of the parquet to work with, and perhaps a few mm more. Can you give us a 'total'?

By LVT, do you mean the flexible vinyl tiles/planks that are glued down?

SWMBO

Bendy_House said:

When you say 'it all needs taking up', what do you mean? Just the thin dampproofing coating, or the whole concrete floor so a proper DPM is laid first?

If the former, then you can only add insulation on top, so I'd suggest you work out just how much you can add. How far can you 'raise' the floor height without causing an issue?! Doors can be trimmed slightly, but you need to avoid a trip hazard at the doorway.

If the whole floor is coming up, then proper insulation should be incorporated in the new slab. I can't imagine for a second that a builder would be entertaining replacing the slab without adding the current regs of insulation, so I suspect that all they'll be doing it laying a new liquid DPM over the existing. Can you confirm?

So, you might only have the thickness of the parquet to work with, and perhaps a few mm more. Can you give us a 'total'?

By LVT, do you mean the flexible vinyl tiles/planks that are glued down?

Yes, vinyl planks - Karndean or similar. 

What has been proposed is layering levelling screed & DPM over the existing base. The parquet is around 1" thick & the floors could be raised more than that if it would make a significant difference since it would only affect one threshold from hall to dining room. 

Bendy_House

Glued-down vinyl planks need a solid base. The screeded concrete would be perfect - except bludy cold (I'm assuming it does NOT have any insulation in it from the 1950's.

Any added insulation would be very thin, because you'd then need a decently-thick ply layer on top to take the vinyl (I'm assuming). So I'm struggling to see how the insulation can be much improved over what you had.

An alternative would be 'click' type flooring, so it 'floats'. This is usually, 6, 8, 10 or more mm thick, and could be laid on fibre insulation underlay, and I think this would have a greater insulation value.

I think what I would do is to work out the absolute max thickness you could get away with, and then contact, say, Karndean (others too) and describe the situation. Ask them what insulation could work, and what needs laying on top of this in order for the vinyl to be glued down.

If they say summat like 'minimum of 10mm plywood layer', then you can work out what insulating type material you can place under this.