Under Slab Vapor Barrier 101 

Very impressed with Stephanie's knowledge but even more with her on cam delivery. Very clear concise and comfortable presentation.

Love to see you highlighting a builder in Utah.

Good information and its great to see other climates covered for their methods. Looking forward to more from Stephanie !

My builder is fighting me on under-slab barrier. We are doing finished slab on-grade and his objection is that if water gets under the slab, the barrier will hold it against the slab and not let it drain. My point of view is that it will stop it from reaching the slab in the first place.

Yay...a contributor in Utah! I'll be contacting her when I'm ready to build.

I’m in Utah. We place a vapor barrier under the footers that runs continuous all the way up the exterior concrete basement wall. Because damp rising. And, Because we’re actual pros.

I would love to see a building science perspective video on the house @MikePatey is building. Its an impressive looking place and I bet there would be a whole lot of geeking out on the technical details. Just the above ground diving/scuba pool is impressive.

Something missing from this conversation is the fact that vapor barriers don't need to be perfect in the way air barriers do. The way that Matt and Stephanie talk in this episode gives the impression that, for "vapor diffusion" the vapor barrier needs to be complete or 100%. For vapor performance the barrier/retarder doesn't need to be 100% puncture free to be effective. If its 95% hole free it functions to bar 95% of the vapor. In terms of Radon and soil gas that is a better reason for making the STO 100% puncture free.

Welcome to Utah, great to see another professional join the Network

We used the yellow stuff in 20 mil and the red stego tape. Loved the system. But we had a lot of trouble keeping it adhered to our well cured and clean foundation. We ended up going back and heating the tape and burnishing it, and still had a few places turn loose just before the concrete was poured.

Yay, welcome to Utah! Dang, as a Utahan, I wish Stephanie had a RU-vid channel. Not willing to use Instagram.

I used Stego on my 32’x24’ garage build. Great product!

Really great video. Thanks for the Vapor Barrier 101.

I watch your videos a lot and I’m always so interested in the build methods. I’m from Hawaii so needless to say many of the homes are different for us here, it’s great to see the level of importance that you put into airflows, insulation and vapor barriers. Many of the homes here are single wall and post and pier with very small amounts of production homes. We have limited building supplies and a small and expensive labor market

What a well orginazed job site, beautiful forming of basement walls well vibrated, but why no expansion joint on floating slab perimeters? As an owner builder of commercial structures for the last 50 years I always insist on a vapor barrier below to keep moisture in during curing and either wet top daily or cover with visqueen to keep concrete wet for 28 days and eliminate internal stresses that are a major cause of future cracking. Ray Stormont

Would be great to see some more videos on insulation for hot & humid climate

I put Stego Home under my basement floor, and bought the tacky tape (grey, adhesive and release paper on both sides) that they show in this video momentarily. It goes down on the footing edge, then pull the release paper on the top and stick down the vapor barrier. We put the tape down all along the footing, which was cured, clean, dry and dust free. Then when we went around pulling off the release paper to expose the adhesive on the top of the tape...the tape would release from the foundation, and stretch, etc. The paper strip on top was stickier than the bottom of the tape stuck to the concrete. It was a big mess, we switched to the red seam tape and taped the vapor barrier that way. But only had purchased enough for seams, so using it for the edges caused me to run out. My foundation guy had a little left over on his trailer, and a roll of some other type of tape, which we wound up using. To Stego's credit, I emailed them and they immediately refunded the $150 or the three rolls of tape, and a regional guy called me to ask for the code numbers from the rolls, he said they had other reports of this happening and he said it might be in issue with some production runs. So for me, it was a big fail, as I did not get the seal between all the concrete and the vapor barrier that I was going for. Maybe I just had bad batches of tape in my case. But it's crazy that the tape was stuck better to the paper on top, than it would stick to the concrete. Everything I read indicated that once it's on the concrete, good luck getting it off. Mine came right off when pulling on the paper on the top of the tape. Crazy.

Very interesting and informative. I’ve learned a lot in such a short time.

Welcome Stephanie.

love the stuff up at 4.20 with the air bubble/seam on the tape...offf

Thanks Stephanie!

Good insight and content in this video thank you both kindly. Good job out of you.

another question is: do you have a vapor barrier under the footings as well? If not what are you doing to prevent capillary action?

I sure hoped you stopped by Temple Square to take in the EPIC seismic upgrades to the temple. They are employing all the latest and greatest building science and techniques on their several projects.

Let’s get going!

Nice mat

Outstanding!

Help me understand. If concrete wicks moisture then why are they not continuing the vapor block up the walls? I get there is protection on the outside but the footers don't seam to be protected.

Can you put this on top of the concrete when finishing an existing basement of a 1960’s home?

Welcome to the Great State of Utah!

I have yet to see a video using the Stego products where the vapor barrier in the floor is tied to vapor barrier in the walls. According to Joe Lstiburek, you should be able to follow the barrier using a pencil on a cross-section view without ever lifting the pencil off the paper. I don't see how that would work in this case.

I’am building a 30’ dia. 6” thk. Concrete slab for a Stargazer dome house. Do I need a vapor barrier as technically I will be putting a floor in it ?

Would like yo have seen an example of what was actually done at the walls to interface with the floor. Or did I miss something?

Joseph Lstiburek says you can walk all over the moisture barrier with golf shoes and it would still perform well

Why not use a wall flashing from Oatey over floor penetrations, taping them in place?

I’d love to see an engineer’s idea using todays technology and build science-how they would replicate Derinkuyu in Turkey. An underground city laugh enough to hole the entire city’s population, animals, food storage, air shafts.. etc.. fascinating concept considering the world today. Replicate the ancient underground cities in various places around the US

She strikes me as super smart and also likes rock n roll. My kind of gal. Looking forward for more content from Stephanie. OK I just watched her bio vid on buildshownetwork and she is super smart.

100% would love to see a @mikepatey build video

I’m in Nevada. I want to meet Stephanie

Is this Mike Patey’s house? 😅 Matt you should go do a tour!

Why no reward or mesh in floor? Or you using fiber

From UK: Those 'mills' can be confusing ;-) I'm assuming the terminology is "thousands of an inch" in US, while I'm far more used to millimeters being abbreviated to 'mills' so easy to confuse. All good stuff.

My basement has a proper vapor barrier. I had a toilet and sump installed. The had to remove a 5’x3’ area of concrete. When they repoured the slab they did not do the vapor barrier correctly. So the whole slab is 45% moisture except that area. Which is 70% sometimes. I had to choose. Try and seal it or try and let it dry. I figured sealing it would push that moisture to the rest of the slab. So I have removed the flooring and just have the concrete open to the air. It stays at 55% now. I’m lucky it’s in a closet so the flooring doesn’t matter much. .

Why is the vapor barrier not on the outside of the foundation?

Geoliners...the whole industry needs to get onboard with encapsulating slabs and basements entirely. So many billions in damages would be saved over time.

Important details that get covered up and never seen again, like they say the devils in the details!

I used 20 mil pond liner as my vapor barrier in my house and my shop.

WY there's no rebar in the basement floor

When you say 6 and 10 mil. You are not talking about mm (millimeter) obviously, so what units are you talking about?

Why are they pouring a basement slab with no rebar in it?

Where is the insulation?

You ought to go to Chicagoland and the adjacent counties up in northern IL and ask why they won't allow PEX plumbing (all must be copper), won't allow romex-type wiring (everything must be in conduit), won't permit wood or engineered wood floor beams for main floors over basements (all must be steel), and hardly anyone does Zipwall, going instead with cheap housewrap and OSB, and most all exterior framing is on 16" centers. Ain't no science going on here. Just deference to the unions. The region experiences hard subzero winters, but there is no focus on energy. And rainscreen walls? Forgettaboutit.

Where does the gas go?

"Concrete is porous" so how are the footings addressed?

Is this the best building style in the event of a nationwide blackout if power grid went down, or a nuclear attack? Would sealing a home tight be the way to go if you have no power to run any a/c, Dehumidifier, exhaust fans etc

Don't know much about vapor barrier but seeing all that uncapped rebar and no safety glasses makes my eyes hurt.

wow no video of the floor great job lol

😄 👍👌.!.

What would the actual additional cost be if you just used good thick plastic? 99% of the cost in this is the labor. Why would you ever lobby to make the plastic thinner or use thinner plastic?

I feel sorry for the people that will buy a house in what sounds like a spring.

It is really hard to compete with second generation knowledge.

10mm? That's not 10mm. What do you guys mean by "10 mil" over there?

Amendment to go from 10 mil to 6 mil…? I need more info. Is 10 mill an overkill? Is 6 mill cheaper crap that boost profit for builder? Where’s the truth and evidence?

Oh lord! The doofy "ON THE BUILD SHOW!" thing is spreading! RUN AWAAAAAAY!

In Texas, they can't build a house that doesn't fall apart in 10 years.

How many hits does it take Matt to drive a 16 penny nail... he's never done it