Insulating a floor prior to laying Karnean advice.

Ye font of singletrack knowledge. We are planning on laying Karndean in our kitchen/diner in our 1920’s built house. Because the house is so old (think Emmental) we would like to insulate the existing floor boards before laying with 9mm ply and the Karndean. If I could get under the house to do this I would but the height is only about 4 foot so that’s impossible. So this got me thinking what could we lay ontop of the boards before the ply goes down? I was maybe thinking of that foil stuff but am unsure how effective it would be. Has anyone done this and noticed a difference? Advice appreciated as always. Juan.

4 foot? surely thats more than ample room to get under and fit insulation from below. My parents house was insulated from below and its only 2-3ft headroom, i’m currently considering whether or not I can do my own house as in areas its around 400mm which I think may be possible just v awkward.

That said it depends on how much height in the room itself you can live with loosing as to what options you have for adding insulation above. You could replace the 9mm ply with a 15mm rigid insulation board and have a floating floor above it? If you’re going to the effort of lining the whole place in ply anyway couldn’t you lift the existing boards fit decent insulation then relay with a thicker ply instead of the old boards plus new ply?

Thanks Thomson, well when I say 4ft it’s more like 3ft (men always exagerate length..) and being 6ft 6″ it’s not easy to move about under the house. I’ve already laid the karndean in the hallway ontop of ply so I don’t want to have a ‘step’ between the hall and kitchen diner if possible. I’d also prefer not loosing any height in the room itself so maybe will have to think of taking up all the floorboards adding insulation then re-laying. The added nightmare for that would be what to do around the kitchen…. Bum, so much for thinking that foil type of stuff would work….

I wouldn’t rule out the foil stuff entirely and rememeber to include that the additional plywood you’re planning to lay will have some insulating benefits also. Just hard to quantify the insulating benefit each will give you. Other option would be to use a laminate underlay material generally 2-3mm thick and is designed to be squashed under flooring and provide sounds and insulating properties.