Green Building Forum - OSB - Airtight Sun, 19 Apr 2026 04:38:59 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255017#Comment_255017 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255017#Comment_255017 Mon, 27 Feb 2017 21:32:53 +0000 fostertom OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255019#Comment_255019 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255019#Comment_255019 Mon, 27 Feb 2017 21:45:46 +0000 djh Posted By: gravelldIf you use a bedding strip does the screw go to the side of that, so two strips per board interface?

Seems very labour intensive?

I'm not quite sure I understand you, but I would use one bedding strip and screw or nail through it if I was using bedding strips. The bedding strip seals around the fixing, and it means the airtightness of the stud is not a factor.

As Tom says, glue is an alternative.]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255030#Comment_255030 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255030#Comment_255030 Tue, 28 Feb 2017 09:30:33 +0000 gravelld
So you have a strip along each line of fixings along an edge?

As I said above, I don't trust glue if it sets hard, but then I don't understand the physics Tom is talking about regarding stiffness of the structure, so maybe that's distrust out of ignorance.

Still wondering about Orcon F, but I guess £££.]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255033#Comment_255033 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255033#Comment_255033 Tue, 28 Feb 2017 10:08:36 +0000 SteamyTea Posted By: gravelldI don't understand the physics Tom is talking aboutDoubt if Tom does :wink:]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255035#Comment_255035 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255035#Comment_255035 Tue, 28 Feb 2017 10:17:19 +0000 fostertom OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255048#Comment_255048 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255048#Comment_255048 Tue, 28 Feb 2017 12:57:10 +0000 djh :bigsmile::bigsmile:]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255049#Comment_255049 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255049#Comment_255049 Tue, 28 Feb 2017 12:57:39 +0000 djh Posted By: gravelldHow does it seal around the fixing then?
I'd suggest getting hold of a bit and having a go.]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255102#Comment_255102 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255102#Comment_255102 Wed, 01 Mar 2017 09:34:53 +0000 gravelld Posted By: djh
I'd suggest getting hold of a bit and having a go. Good, and accurate, answer. :tongue:]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255111#Comment_255111 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255111#Comment_255111 Wed, 01 Mar 2017 15:52:12 +0000 barney
To answer another question - there has to be a design life - it may well be that we use the building beyond that, but no designer will sign up to a product with an infinite lifespan

Any architect putting an infinite life on a building is either so old they'll be dead before any problems arise, is so reckless that they are probably uninsurable or so stupid as to be not worth employing

As I said, for other than very small buildings I'd not be missing out on expansion joints. FWIW, I've seen air tests run in something akin to a hot box where OSB is correctly installed to studs with a 3mm expansion joint and we've then proceeded to put some pretty big fans into one half to measure leakage rates - it was actually pretty impressive - more than adequate to combat a 500Pa overpressure and to maintain a specific gas concentration on the test side - it did improve when the stud was tacked with 3mm closed cell foam and then the sheet material nailed on (ring shanks and air nailer) the improvement was actually that spectacular however- these were "proof tests" we did for a PFI school building (that was likely to be replicated in a number of locations with different "outer claddings"

Regards

Barney]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255114#Comment_255114 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255114#Comment_255114 Wed, 01 Mar 2017 16:53:16 +0000 djh
Did they perform airtightness tests both with overpressure and underpressure? It's the situation where the nails are in tension that would concern me more. Also the situation after a few years of seasonal movement and possibly shakes developing in the studs. That's when I would expect compression gaskets or flexible glues to earn their keep.

I'll try to remember to run another airtightness test after we've been here ten years, or earlier if anybody wants to fund it. That should show something about membranes and tapes, as well as wet plaster.

Just out of interest I went looking and according to http://www.siga.ch/en/company/company-history.html Rissan was launched in 1994 followed by Sicrall in 1997. So they've been around for over twenty years - I wonder if any independent tests have been done of the first installations?

Pro clima claim on https://proclima.com/service/100-years-adhesion "Re­li­able func­tion­ing tested for 100 years
In­de­pend­ently con­firmed", but they are lying of course. They have tested their products in an accelerated aging programme for 700 days. I have no idea how realistic the results are, though I expect there are experts who do.]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255119#Comment_255119 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255119#Comment_255119 Wed, 01 Mar 2017 18:15:50 +0000 ringi OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255121#Comment_255121 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255121#Comment_255121 Wed, 01 Mar 2017 18:56:19 +0000 fostertom Posted By: djhI wonder if any independent tests have been done of the first installations?That would be very valuable, but I'd understand if the cos aren't keen to open that can of worms!

Posted By: djhAlso the situation after a few years of seasonal movement and possibly shakes developing in the studs. That's when I would expect compression gaskets or flexible glues to earn their keep.
Exactly - except the bit about flexible glues? My feel for it is that specifically rigid glues (which tho gapfilling are (initially) pulled down near-zero thickness in enough spots to minimise any elastic/shear movement) would fare better - uncompromisingly holding things motionless - and not releasing that hold when timbers shrink enough to let let nails/screws go slack.]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255124#Comment_255124 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255124#Comment_255124 Wed, 01 Mar 2017 19:54:12 +0000 barney
Yes, we did both overpressure and under pressure - OSB nailed with full head ring shanks and at the correct centres (which are often tighter than your average installer imagines) showed no hint of moving at 500Pa positive and negative (for the actual application, there can be significant underpressure during the gas release cycle)

If the studs are going to move about then most certainly nailing into a resilient bed would outperform any rigid sticky stuff - it only has to move once and it's "gone" as a seal

I think my point however was that well nailed OSB with adequate bearing onto the stud (which could of course be metal with screw fixings) performed remarkably well at 500Pa - which is probably a lot more than local wind pressures. I would suspect that interfaces between elements are the weak points in reality - doors and windows to walls, walls to roofs etc. The test box did actually show a dramatic fail when we lost a short section of silicone mastic between the panels and the enclosure - it was very short section at a corner, not intended to be part of the test, but when it failed, it totally dominated the leakage - it had just shrunk back a little from the box, rather than the OSB

Regards

Barney]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255129#Comment_255129 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255129#Comment_255129 Wed, 01 Mar 2017 20:53:18 +0000 Ed Davies Posted By: barney500Pa - which is probably a lot more than local wind pressures.½ρv² gives 28 m/s or 62 mph - top end of storm force 10. That's simple “face on” dynamic pressure, not any sort of aerofoil lift. Not a case you'd worry about a bit of leakage but certainly wouldn't want failure at those speeds, e.g., cracking of ridged glue which is then leaky forever more.

>>> math.sqrt(1000/1.28)
27.95084971874737
>>> math.sqrt(1000/1.28) * 3600 / 1609
62.53763765537013

That's almost worth remembering: 100 km/h wind gives 500 Pa pressure.]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255131#Comment_255131 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255131#Comment_255131 Wed, 01 Mar 2017 21:31:28 +0000 SteamyTea Posted By: Ed DaviesThat's almost worth remembering: 100 km/h wind gives 500 Pa pressure.Had a few days of them recently.]]> OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255133#Comment_255133 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255133#Comment_255133 Wed, 01 Mar 2017 23:50:51 +0000 fostertom OSB - Airtight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255145#Comment_255145 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14931&Focus=255145#Comment_255145 Thu, 02 Mar 2017 13:38:46 +0000 gravelld Posted By: djh
Just out of interest I went looking and according tohttp://www.siga.ch/en/company/company-history.html" rel="nofollow" >http://www.siga.ch/en/company/company-history.htmlRissan was launched in 1994 followed by Sicrall in 1997. So they've been around for over twenty years - I wonder if any independent tests have been done of the first installations?
I thought I read/heard recently they had opened up one/some of the original Passivhauses and found them in good nick? But not sure if they used tape or not...]]>