concrete vapor barrier

[lynnbilodeau]

Getting ready to pour about 1300 square feet of concrete on part of my shop floor. Long story. Building was built in 1919. May do a full thread on the rehab, but not now.

Short version.

Water table was very high (like two inches below grade!!!)

We installed about 400 feet of perforated pipe and the table is coming down nicely. Soil is very heavy damp clay that has been saturated for over a century.
After excavation (we only need two or three more inches of soil to come out) I am placing a geotextile stabilization fabric, similar to what is used under concrete interestate highways. This will help stabilize the soil. Then 4 inches of compacted gravel for a capillary break as well as further stabilizing. Then a heavy duty vapor barrier with all the seams taped securely. Then 5 inches of reinforced concrete.

I see that Home Depot (I know, some of you guys think every bb store is evil) has a barrier that would work fine. However, I am not a concrete specialist. So, my questions are:

1. Does this look like it would do the job OK ?

https://www.homedepot.com/p/HUSKY-1...w-Guard-Vapor-Barrier-CFYG1514-140Y/204172012

2. If not, is there an alternative that would be better, for not much more money?


Thanks in advance.

Lynn

 

[mcbane]

The Husky product looks like a knock-off of stegowrap. If you have a nearby concrete supplies store, you should be able to buy the genuine article for less $ than the knock off. For example: https://www.cmcconstructionservices.com/stego-industries-llc-vapor-barrier-size

 

[ConCretin]

The requirements for a vapor barrier depend on your plans for your slab. The primary purpose of a vapor barrier is to prevent water vapor from affecting adhered floor coverings. If you envision the possibility of a nice epoxy floor, then spend on a quality 15 mil product and pay attention to the details when you put it down. Otherwise, lay down some 10 mil poly and spend the money elsewhere.

 

[Copymutt]

Caution, If that’s expansive clay, it will shrink as you get the water out, not good. Even worse when it gets wet again. Soil engineer can keep you on track if it needs to be overdug and replaced.

 

[Retroman]

Spend the money and get class A 15 mil Stegowrap, Yellow guard or equivalent.

 

[joes169]

Just my professional opinion, but I'd lay 2 layers of standard 6 mil vapor barrier before spending that kind of money under a concrete shop floor that probably won't ever be an issue, anyways. One layer of 10 mil would be a good option, as well. If you have any control over the concrete pour/placement, that can go a long ways, as well. We have special "cradles" on the front of a few wheel barrows that work perfect for vapor barrier pours, as they don't pierce the VB when dumping.

 

[lynnbilodeau]

Thanks all for your input.

 

[bmwpowere36m3]

Try a local construction supplier... when I called about 15 mil vapor they wanted $300 for identical roll size.

 

[rotortuner]

I used the same product your looking at from home depot on 4k sqft over compacted 1/4 minus and it worked well. I didn't have the water issues your talking about though. the other guys might be right in being able to find it somewhere else for cheaper but my experience out west here is that home depot buys in such large quantities they beat the price from any smaller place. I used the red 3m tape and it was ok and probably cheaper for the large sqft. if you want it to be really water tight might want to look at duct tape. order some tape ahead of time to figure out what you think is best. the 15mil your looking at is thick and its good stuff, quite heavy duty.

 

[Jazz1]

Looks like Stegawrap. More durable than vapour barrier. Its used locally as vapour barrier for concrete. I used it in a crawl space, dropped humidity in house from 60% to 40%.
I put a layer in my wigwam to keep moisture out during storage as these portables are little more than a greenhouse sucking all moisture out of the ground where a old vehicle can absorb it.

 

[bdk1976]

I used this stuff under my slab that was poured a couple of weeks ago. May be overkill for my slab but pretty much everything else about it is as well. HD overpriced - I think I paid somewhere between $300-400 a roll from a local concrete supplier.

 

[Jason B]

Lets see some pics of a vapor barrier before the concrete is poured. Any pics will do. We talk about this all the time and I've never seen a photo.

 

[lynnbilodeau]

Sorry I did not see this before the pour. However, there is a 6 x 6 area around an existing well (that's right, they built this building over an existing well in 1919), and I can show you a pic of the vapor barrier before I concreted in the manhole cover.

I only have phone pics, and have not sorted through them yet. Will do so soon.

 

[lynnbilodeau]

Here is a picture. The vapor barrier is the green. The red is the heavy duty tape for sealing the seams.

 

[spike99250]

I agree with LLWillysfan that ten mill should be fine. It was all we used for years. Now the 15 mill seems to be the new spec.

That being said,If you can afford it, go for it(you don't get to do it again).
My recommendation though is you can find the Stego tape(doesn't matter what brand the plastic is)get it. The husky tape was a bear to pull off the roll, didn't stick as well, and was harder to use around penetrations when flashing.

Myself and three other guys just spent the last three months placing this type of vapor barrier down. I believe it was the yellow guard.
We are building a new high school and I was on the floor prep crew(vapor barrier, bulkheads and expansion joints). They shut down the floor pours for the winter, but we will resume in the spring. Kinda sick of seeing yellow

 

[Marctrees]

Another benefit of "VB" under concrete pour is to keep the hydration IN for better curing, NOT allowing water to seep away.

Edit add - Doing this though, keeping the water in, will increase longer total finish time.

But it is a better end product.

Marc

 

[Honolulu]

Based on the "well" picture let me advise... Don't EVER let the rebars fall to the bottom of the slab, they are nearly worthless in that position. Use "chairs" (broken hollow tile or other) to keep the rebar at mid-depth of the slab.

 

[Jason B]

Lets see some pics of a vapor barrier before the concrete is poured. Any pics will do. We talk about this all the time and I've never seen a photo.

^^^^^^^^^^^^^

 

[ConCretin]

Lets see some pics of a vapor barrier before the concrete is poured. Any pics will do. We talk about this all the time and I've never seen a photo.

^^^^^^^^^^^^^

Check out the Stego website for some pics and a bunch of other information;

https://www.stegoindustries.com

 

[rotortuner]

Here’s some

 

[lynnbilodeau]

Based on the "well" picture let me advise... Don't EVER let the rebars fall to the bottom of the slab, they are nearly worthless in that position. Use "chairs" (broken hollow tile or other) to keep the rebar at mid-depth of the slab.

I agree. I didn't have any chairs handy, so when we started to pour, we held it up with rakes until there was about 4 inches of concrete, under them, then let them rest there. The rebar is all mid slab.