1

I am in Ireland. I have a semi-detached two storey house. On the ground floror, on room has a suspended timber floor while others have a concrete floor. And the room with a suspended timber floor is the coldest in the house, with draught from below the floor clearly happening.

I am considering putting insulation above the floorboards, as taking them up is a huge and risky job. However, I can't work out just how to stop the draughts. Foam-based floor insulation appears to require an expansion space around it, and nothing would stop air from flowing in that expansion space. I would not trust a mere polythene membrane to stay intact long-term (in fact one appears to be installed in the existing floor). So what kind of insulation layer can I use to make the floor airtight?

I would hope that an airtight floor does not create a rot issue because the floor is still ventilated from below.

Improve this question
4
  • 1
    Pictures would be helpful from the underside if possible
    – UnhandledExcepSean
    Commented Dec 13, 2022 at 2:42
  • 2
    Do you have access to the underside of the wood floor?
    – RetiredATC
    Commented Dec 13, 2022 at 4:54
  • 1
    Wall to wall carpet might go a long way to "sealing" the floor
    – Kyle B
    Commented Dec 13, 2022 at 6:04
  • I do not have access to the underside, which is a shallow ventilated space but the ventilation grate is not removable. I want to avoid carpet if at all possible, and besides carpets are not airtight.
    – Mikhail Ramendik
    Commented Dec 13, 2022 at 17:03

2 Answers 2

Reset to default
1

Check local code, of course, but folks have sometimes installed sheets of foam insulation across an entire subfloor, then installed flooring on top of that. If I had more ceiling height I'd consider doing that in my basement. Sorry, I don't have details, but websearch will probably find examples; I've seen mention of it in discussion of workshop design and because one insulation manufacturer mentioned it in application notes for their product. "If it happens, it is probably possible."

Improve this answer
0

Sounds like the problem is mostly the wind getting through the cracks.

Fit carpet with the highest quality underlay you can find. That will prevent draughts between the boards and if it's thick enough it will also stop draughts under the skirting boards.

Alternatively install a floating floor (laminate, bamboo, engineered wood, etc) on top of a suitable underlay. The underlay will be a bit different from carpet underlay but provides similar benefits. Ours was foil-faced foam, maybe 5-10mm thick, came in a roll and installed with foil facing down and seams taped. The "click-fit" floor holds in all in place. I think you can also get rigid fiber underlay of a similar thickness.

With either method, it's worth doing something about the gaps around the edges. Our floor fitter didn't seal before installing the skirting boards and I've had to go round with flexible caulk. It would have been much better to have run the underlay up behind the skirting or filled the gaps at the edges with expanding foam before the skirting went on.

(Sorry - I looked for photos of when our floor went down but couldn't find anything useful.)

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.