Go to Forum Home Building Refurbishment and Retrofit Vapour barrier for suspended timber floor

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    • #31964

      Hi AECB community

      We are currently retrofitting a 1930s semi-detached house in Cumbria. The ground floor is a suspended timber floor with a large void beneath. Our plan is to put mineral wool batts between the joists and a vapour permeable membrane fastened underneath. We have 2 questions relating to this:

      1) What sort of vapour barrier would people recommend above the floorboards? For example, could we use hardboard with taped joints and taped to parging behind skirtings?

      2) Should central heating pipes be run within this insulated floor or should they be clipped to the underside of the joists?

      We are new to highly insulated and airtight construction methods, so any advice would be really appreciated.


      Clym and Ellie

    • #39229

      It's important to remember that there are two types of hardboard – standard and oil-tempered. I believe oil-tempered hardboard can serve as a vapour barrier but 'standard' hardboard is vapour permeable. Indeed it is sold as a proprietary external 'breathable' racking board.

    • #39230

      Thanks for your replies Geoff and Dave. They are really helpful.

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