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WILL1E
Moderator
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# Posted: 15 Feb 2022 08:07am - Edited by: WILL1E
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I'm getting pretty close to the point where i'll be putting up the vapor barrier in the ceiling of my cabin build. I thought i had the details noted somewhere, but apparently not.
-What are the rules of thumb for how much overlap i should have at the seams of 2 or more pieces?
-How much should the ceiling vapor barrier overlap the walls?
-Is there a specific tape i need to use on the seams?
-Anything else i need to know when installing it?!
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Steve_S
Member
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# Posted: 15 Feb 2022 09:10am - Edited by: Steve_S
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2-4" overlap and use Accouti-seal as the sealant between the plastic sheets (Super Gooey & Stickey and always stays like that, so wear gloves & stay tidy, it is a Nasty Clean up). I used standard Red TechTape for sheathing to seal the seams as well...
REF: https://www.homedepot.ca/product/lepage-pl-acousti-seal-sound-absorbing-vapor-barrier -adhesive-black-flexible-825ml/1000409510
Remember to put all seams overlapping the inside so they are all cascading over the sheet below starting from the top. 4-6" Overlap is quite sufficient.
Staple it all up well and snug but NOT Overtight or stretched. Only once all installed, proceed with whatever drywall or paneling you want.
Be gentle with the plastic in corners & tight spots, if too loose it can bunch up and cause issues & if too tight it may be challenging to get panels in tight. I suggest using a long think hard edge (10" muddingblade is good) to tuck into corners and such before stapling, it WILL save much grumbling.
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Aklogcabin
Member
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# Posted: 15 Feb 2022 10:06am
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We call acoustic caulk black death. Use along the seam where the bottom plate of the wall studs meets the floor. I generally put the visqueen up then go back n do the seams n edges.
Place is looking good man
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travellerw
Member
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# Posted: 15 Feb 2022 10:37am - Edited by: travellerw
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On a vertical seam, I like to overlap 1 stud bay if possible. That allows you to staple both the sheets to 2 studs. On a horizontal seam I overlap about 6". If you are looking for "Belt and braces" then use acoustical seal and tape for each seam.
For tape, the code was changed up here some years ago and Red tape is no longer allowed on vapour barrier (Red is now for external materials like tyvek/typar). There is a Blue tape that is now required on vapour barrier. They say the adhesive was reformulated to stick better to vapour barrier material (IDK seems the same to me, just blue colored).
Both tape and acoustical seal around windows. Be meticulous here. Windows are already cold zones, you don't want more cold air leaking in around them.
Acoustical seal along the bottom where the suds meet the floor. Staple and press the vapour barrier into the sealant to ensure a good seal.
Finally, ensure you have not pulled the plastic too tight, especially in corners. You need to make sure the plastic is layed nicely in the 90 degree corners or you will be super angry putting up drywall.
(P.S. If you are looking for some make work projects for the kids! Get them to cut small pieces of tape and tape all the staples. Really not required, but it sure keeps them occupied for a while ;) )
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BRADISH
Member
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# Posted: 15 Feb 2022 11:35am
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Sorry to somewhat hijack this, but since we seem to have a few folks with experience - Do you still put a plastic VB over the kraft faced insulation?
There seems to be quite a few opinions floating around that say the kraft facing IS the VB, which just doesn't seem right to me.
Otherwise, great thread. I am taking notes.
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Nate R
Member
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# Posted: 15 Feb 2022 12:02pm
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For a VAPOR barrier, Kraft facing is fine, but harder to install batts properly with it on.
For an AIR barrier, that's a different story. I think this adds to the confusion.
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ICC
Member
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# Posted: 15 Feb 2022 12:15pm
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info link
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WILL1E
Moderator
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# Posted: 15 Feb 2022 03:36pm
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Quoting: Steve_S Remember to put all seams overlapping the inside so they are all cascading over the sheet below starting from the top. 4-6" Overlap is quite sufficient.
What's the reasoning/theory for this?
The red tape is all i'm finding online locally for HD or Menards. @ Nate R do you know if this is called out specifically for code on what we can use?
As for the black gooey stuff, i'm not finding anything online. Might have to go to the stores and ask what they normally sell. I think i've seen folks use it where the subfloor and bottom wall plate meets, but never anywhere else. Is that normal practice?
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Nate R
Member
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# Posted: 15 Feb 2022 03:41pm - Edited by: Nate R
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Not sure what code says on this....
Ok, just looked, and found just this: URL
So, looks like it's fine as long as you have something, and it's below 1 perm... (which plastic is), and it doesn't specify a tape.... and says NO tape needed around doors/windows. Interesting.
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travellerw
Member
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# Posted: 15 Feb 2022 04:03pm
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I think the blue tape thing is only up here in Canada.
I also find it strange that acoustical sealant isn't a name recognized down there. Its basically a non-curing butyl rubber sealant.
https://www.lepage.ca/en/lepage-products/build-things/sealant/pl-construction-sealant /pl_acousti-seal_vapourbarriersoundreductionadhesive.html
I'm guessing its just called by another name down there.
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Irrigation Guy
Member
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# Posted: 15 Feb 2022 04:30pm
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Funny, I have been in the trades for 22 years here on Long Island and I have never seen a vapor barrier installed in a home. That being said I had to install one in my cabin because because of roof condensation issue. I made a mistake when constructing the metal roof (bare metal on purlins).
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travellerw
Member
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# Posted: 15 Feb 2022 04:30pm
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Quoting: WILL1E What's the reasoning/theory for this?
I'm sure Steve will come back and answer... but if moisture gets behind the drywall, you would rather have it run down and leak between the drywall and vapour barrier, instead of behind the vapour barrier and into the insulation and stud cavity. In the event of a big leak you will see the issue quicker. In the event of a small leak, the moisture isn't slowly killing your insulation.
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gcrank1
Member
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# Posted: 15 Feb 2022 04:55pm
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As in 'think shingling'.
I did that type of thing with everything behind my walls, including/especially the shower unit, when I rebuilt our home bathroom. IF I ever get a leak in the shower piping I want the water heading toward the shower floor-pan not into the walls.
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Steve_S
Member
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# Posted: 15 Feb 2022 05:12pm
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The reasoning is much as Traverllerw says, it's ultimately essential to keep any moisture potential away from the insulation. Regardless if fiberglass or rockwool.
I've done several vapour barrier installations, it is normal practice up here which is to also include an air exchange system to prevent getting into a sick house condition.
*Sick House is a reference to moulds, mildews and other harmful conditions which thrive in damp conditions which can create illness. This became a predominant issue once air-tight homes such as R2000 level became common.
NB: I have renovated badly retrofitted air-tight homes which had fungus & even mushrooms growing within the insulation and between the drywall. Breathing Equipment was absolutely required ! Repair & Remediation was "nuts".
Picture the structure, with insulation installed, the vapour plastic around outlets & switch boxes (see image below) and all of the plastic up. Envision how water spray would flow down that plastic and just where it will seep in and leak... it all has to run down to the floor with the least interruptions. If it can catch anywhere, that is where you will have issues... Bathrooms & Kitchen spaces are the worst offenders obviously and depending on structure have to be dealt with accordingly. Cabinets, Fixtures & fittings can all introduce issues. Vent Pipes are nefarious as well for collecting condensation ie Bath & Kitchen, Dryer even...
There is also a Gotcha lurking here. As my final build (my current home) was built exclusively with sheet foams, they are actually a vapour barrier as moisture cannot enter it be retained by it and is air tight of course when properly installed.
ALWAYS FOLLOW YOUR REGIONAL CODE REQUIREMENTS & SPECS ! What applies to us here may not apply to you elsewhere. That applies to electrical, structural and resource "water" usage etc...
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