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10-06-2019, 14:17   #1
Idbatterim
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rockwool, best way to hold in place for log cabin?

hi lads, helping a mate with his small office log cabin, the joists are sitting on ground screws. There is weed membrane down. Then 6 x 2 timber for the joists. I read a guy saying chicken wire not good to hold up the rockwool as rodents can get in. How about a sheet of building plastic? or would that cause condensation issues? I also believe we should leave a gap between the top of the rockwool and the osb, is that correct? Just going on stuff I saw on youtube. thanks!
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10-06-2019, 19:45   #2
Lumen
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Rule is: air tightness on warm side of insulation, wind proofing on cold side. The point of windproofing is to stop large volumes of cold air blowing through the insulation.

If you can lift the frame up enough for access, I'd be inclined to use mouse mesh with a windproofing membrane both flat on the bottom of the joists.

My pics and notes from doing the other membrane-over-the-joists approach last year:

https://www.boards.ie/vbulletin/show...9&postcount=84
https://www.boards.ie/vbulletin/show...6&postcount=91

I would not leave a gap on top of the insulation, no idea what that's about.

Last edited by Lumen; 10-06-2019 at 20:04.
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14-06-2019, 17:37   #3
Idbatterim
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thanks for the very informative reply! so you just went up and over the joists, a pain in the ass like you say, I realised this myself without having even started it! Did you just tack it in or use a staple gun etc? Any idea where I can get that membrane? Thanks!

he is now thinking it might be easier to go with PIR board, just held up by strips off thin wood and this would negate the need for any membrane etc underneath?

Last edited by Idbatterim; 14-06-2019 at 17:55.
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14-06-2019, 18:18   #4
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Quote:
Originally Posted by Idbatterim View Post
thanks for the very informative reply! so you just went up and over the joists, a pain in the ass like you say, I realised this myself without having even started it! Did you just tack it in or use a staple gun etc? Any idea where I can get that membrane? Thanks!

he is now thinking it might be easier to go with PIR board, just held up by strips off thin wood and this would negate the need for any membrane etc underneath?
I got the membrane from Ecological Building Systems in Meath. I needed it for the outside of the walls and roof so it made sense to use it elsewhere, but it's expensive and the PIR idea doesn't seem to have any downsides I can think of.

I dunno whether rodents will eat PIR but you could use mouse mesh and tek screws (or similar) to hold it in place, solving two problems in one.
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