DIY
Does crawlspace vapor barrier need to be taped?
Hi I went into my mom's crawlspace and it seems ok, dry, barrier was in good shape, insulation looked nice, but i noticed that the barrier is only taped on the seams, but not along the posts, or concrete. Is this ok, or should i go down and tape it all?
Discussion
it is best trade practice if it is taped and highly recommended..
in saying that...
i have seen no rules or regs that require it in the situation you have above..
IRC section R408.1 Ventilation - when using a vapor barrier to get the reduction it is implied that the barrier is continuous, which means taped joints.
IRC section R408.4 Unvented Crawl Spaces - it explicitly states sealed or taped.
that documented clearly applies to non vented crawl spaces which does not apply to the OP's pic..
that document also makes no reference to piles etc being taped.. only the tapping of laps which is standard procedure..
i accept requirements may vary from region to region but this reference material you have quoted is not relevant to the OP's question..
The code requirements say basically the same thing in every instance a class 1 moisture barrier is used except in the ventilation section referenced. In my opinion, the requirements for sealing it would also apply here since it's vague and does not explicitly say otherwise. The purpose of the barrier is to retard moisture. Having opening and holes in it removes its purpose.
Op has a vented crawl space with a moisture barrier installed. Since it's installed the code section R408.1 permits less vents to be installed per sq. ft. OP could check the sq. footage to determine if it's even needed at all. If it is, then it should be installed properly and in accordance with the Mfrs. recommendations and requirements of the code. Most all Mfrs. say to seal all joints with min 6" overlap, seal against foundation and seal around all penetrations. That would include the piers.
Because I have the maturity of a 8 year old, I must laugh inappropriately when I read "MFrs."
But thank you for your feedback
Retard means to slow down not to stop. Its doing its purpose.
Huh, is that what that word means?
Best practice is to. Otherwise it's like putting plastic wrap over your leftovers and poking a bunch of holes in it. Moderately effective at best. Vapor... Retarder?
In this case it’s better to go full vapor retarder
Never go full vapor retarder.
I heard Sean Penn went full vapor retarder at his mom's place. His mom was not happy about it so sent him home empty handed without any leftovers.
I'm surprised no one mentioned it. Do not cover wood in plastic. Do not. It will begin rotting prematurely. The vapor will have no place to go but the wood
This is big. I would be more concerned about the wood touching the ground and being sealed in with the vapor.
Thanks for mentioning this, I would have probably taped onto the piers like an idiot
Having done service work in aged crawl spaces, the better sealed the better they keep.
If you have any commonly accessed areas like water controls or hvac equipment, make paths with old carpet, plywood, or even cardboard. A few passes will see the vapour barrier damaged.
Great tip, thank you
I taped mine as best as I could, but it's got some gaps and is not completely sealed, yet within a few weeks of installing I was noticing our floorboards drying up and gaining some extra cracks, so assume it's working, plus I've left a whole row that I haven't gotten around to finishing, will be tackling that in the summer when it's not so cold down there.
Yes,. Also, There’s an adhesive that works better in those areas (to concrete) in my experience - nu flex 446. It’s non-drying- so make sure whatever you’re locking down is final.
To be a vapor barrier it needs to be vapor tight
It's not effective with gaps like that, so yes.
What's the project?
Yes
If you're mitigating anything like radon, moisture... Basically whatever the barrier was put in place to do, YES.
It's called a barrier for a reason. Not a fitted sheet.
Its only there to slow down vapor not to stop it. You just don't want alot of water vapor being dumped into you house at once so this limits it. A typical house is designed to leak. If you wanted more dry buying a dehumidify and putting in basement generally the next step. If you were to seal it completely you would be trapping moisture and anything that could rot would now rot that is under the plastic.
I am getting some differing opinions on this, but your take makes alot of sense.
Mine is staked down
Yes, with Scotch tape. You'll need at least one roll. /s
Air. Tight. Mofo... It's not a barrier if just a redirect
uhhh, ya.
What is it doing? You don't want to trap moisture in your insulation, you want to prevent moisture from getting into the insulation. So IMO the vapor barrier should be on the other side of the insulation (directly beneath the floor), and the insulation itself should be allowed to breath, like now. My understanding is basic though, I don't understand the function of this plastic foil, the way it is "installed" here, but I would be hesitent to seal it off before I understand what it does. I don't think it's a good idea to make the whole crawlspace air-tight because it's not insulated and moisture from inside the house could lead to crazy condensation down there.
Overall it looks fine to me like it is, I would monitor humidity and temperature in there for a while to get a better picture (compared to outside and in-house)
The installation guide says only 80% coverage is required for moisture control. That said a roll of vapor tape is $15, looks better, is more efficient and is overall best practice.