high-tech membrane under suspended timber floor ?

[brugnospamsia]

Dear group,

It is my intention to replace my upstairs floors with chipboard, enabling me to re-use the boards downstairs for a sanded floor. As I will be improving the ventilation under the ground floor, I hope to staple netting between the joists and insulate with 50mm of mineral wool.

I Googled for info on sealing draughts in non-tongue_and_groove and mostly found the usual papier mache and solid wood fillets solutions.

I'm wondering if breathable roofing membrane directly under the boards might be a better solution (or maybe used in place of netting to suspend the mineral wool ?)

Jeremy

[Mike]

I've used the foil covered Airtec stuff Screwfix sell as it forms a condensation barrier as well. Also I used Kingspan instead of mineral wool (second quality is fine in this application) rammed between the floorboards as it insulates better.

[brugnospamsia]

floorboards

Sorry to be dense, but is this what you mean ?

thanks ...

Jeremy

[Anna Kettle]

Yes, but to a diffrent problem. The papier mache and solid wood fillets solutions provide some insulation but primarily are there to stop things falling down the gap

Anna ~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[brugnospamsia]

I have to say that since I'm planning to leave gaps between the boards (though maybe not quite of "Brighton Pier" dimensions), I'm starting to wonder just how long it'll take for the void to fill up on top of my insulation - though my intention is to improve my lifestyle to the point of housework ;-)

I suppose I might need to get a discriminating metal detector if people start dropping valuables on my floor ;-)

[Mike]

Airtec over the top of the Kingspan and over the top of the joists so that before you lay the floor all you can see is Airtec.

If the floor has been fitted then you could instead run the Airtec under the bottom of the joists as well as under or on top of the Kingspan. The problem with this method is moisture could be retained against the joists so you need to build in some slack so that any condensation drains away from the joists, not towards them.

Either way gives you want one continuous run across all the joists, then taped up in parallel to give a complete impervious sheet.

[brugnospamsia]

I used Unibond bathroom and shower sealant from the local shed. Expensive at 8 quid a go but it's so bloody waterproof it's v.difficult to smooth it after application 'cos it sticks to

*everything*. Flexible too, the only thing that broke it in our case was for some reason the shower tray managed to drop a few mm (don't ask why, I dunno yet!) and the stuff stretched and broke the grout on the surrounding tiles resulting in much leakage.....

The moral to this tale is if yer tray doesn't drop this stuff is good! IMO obviously.

cheers

witchy/binarydinosaurs

[Mike]

They breathe in the area under the floor - which is what they were designed to do of course. The Airtec will squash almost flat between floor and joists.

If they are nice floorboards you want to have on show then use blind nails. These are nailed through the tongue such that the groove of the next one can still fit home tightly. You'll also need tho hire the special tool to compress them together properly.