Vapor Barrier

[Dustin Crawford]

Hey guys. I am getting ready to tie rebar soon for my floor and was wondering what you guys use for vapor barrier.

I would rather use plastic than sand, but dont know if there is a certain thickness or specific stuff I should use?

Any help would be appreciated!

DC

 

[LegacyIndustrial]

6 mil plastic sheeting.

 

[Mark H]

Hi Dustin.Recently laid a slab for my new garage.I used 1 inch of sand over the ******** to protect the sheeting from punctures,then laid out 1200 guage polythene damp proof membrane.If you have to joins in the membrane,overlap them by at least 12 inches and tape the joint.
Hope this helps.

 

[dcs Inc]

Go a minimum 10 mil visqueen. Get a good water proof tape and tape all over laps and around anything that protrudes through the plastic. This is very important to protect your floor for water migration.

Now: Most garage spaces are dug out to the foundation line. The house foundation block/poured walls are installed and then the space for the garage is filled with pea gravel. This area can be a few inches to several feet. Track homes normally elevate the floor well above the ground height and then back fill up to the house foundation. This allows for positive rain flow away from the home itself, especially if theirs a basement involved. This type of garage will have ample drainage under the slab.

Unfortunately, the visqueen (plastic) sheeting today has degraded to the point where it doesn't hold up very well. The last project I applied a vapor barrier to I decided to up the anty and used a 15 mil vapor barrier plastic sheeting. It was as thick as a pool liner. I will never have to worry about it degrading and falling apart.

I can pull up some astm and aci recommendations and all that **** if needed but what I have stated is the norm. Depending on which state you are from, most are requiring a 10 mil.

gene ec-Indy

www.indycrete.com
www.elitecrete.com
www.elitecreteindiana.com

 

[pauls340]

The problem with vapor barriers is they do absolutly nothing to or for the free water in the concrete. On a 4" thick slab there is about 32 gallons of water in a cubic yard (81 sq ft) of concrete. Of the 32 gallons approx. 15 gal is used to "make" the concrete leaving approx. 17 gal of free water to cause all sorts of problems. I didn't spend a penny on a vb, I applied Vapor Lock which uses that 17 gal to make additional CSH Gel. Three years later, zero moisture from day one, any paper, wood, or steel you pickup off that floor, it is 100% dry. Google Vapor Lock, good luck

 

[Dustin Crawford]

Thanks everybody. So this vapor lock. Is that an admixture to the concrete brought in by the truck, or a spray on sealer for after? I cant tell from the info I found.

Does sealing the top of the concrete after the pour do the same thing as a vapor barrier?

 

[pauls340]

Vapor Lock 20/20 is an admix and the 0/0 is the sprayon. I used the sprayon. Waited 4 hrs after the concrete was placed, took my boots off and sprayed two coats. I think the website tells where you can buy it.

 

[dcs Inc]

The problem with vapor barriers is they do absolutly nothing to or for the free water in the concrete. On a 4" thick slab there is about 32 gallons of water in a cubic yard (81 sq ft) of concrete. Of the 32 gallons approx. 15 gal is used to "make" the concrete leaving approx. 17 gal of free water to cause all sorts of problems. I didn't spend a penny on a vb, I applied Vapor Lock which uses that 17 gal to make additional CSH Gel. Three years later, zero moisture from day one, any paper, wood, or steel you pickup off that floor, it is 100% dry. Google Vapor Lock, good luck

OK, are we talking about a topical to seal in the moisture in the concrete or actually preventing moisture from entering the concrete? There are a lot of surface vapor barriers that can be applied to the surface that will hold back a certain amount of emissions but why screw with that if you can prevent it in the first place. The moisture will dissipate from the slab during the curing.

We have a vapor barrier epoxy that will hold back 12 lbs of pressure but if the slab hasn't been poured yet why would one depend on a topical method of prevention? Get a hair line crack in the concrete and there goes your pretty epoxy coating.

Maybe I'm missing something here on the thought process. Paul, have you actually done any moisture tests on the concrete to see if there is any vapor emissions? The most accurate testing is a rapid humidity test. Even if you don't show any "wet" areas after pulling up the rug, moisture still exists and if over the recommended amounts of the non breathing seal coat, will cause a major failure to the topical coating. gene ec-Indy

www.indycrete.com
www.elitecrete.com
www.elitecreteindiana.com

 

[ConCretin]

I'm sure the surface applied vapor barriers are fine and a good option for floors that did not have a membrane type installed during construction but I would opt for the latter.

The free water in the concrete will work its way out of the concrete over time and is not a problem long term.

If you don't intend to cover the floor with an adhered covering, 10 mil poly is probably fine. If you anticipate you might install an epoxy or something similar I'd upgrade to a specialized 35 mil product like Stegowrap. The system includes tape for the seams.

The Stego will resist damage during placement and not degrade over time.

 

[LegacyIndustrial]

Use the sheeting as LLWillys and the others have suggested.
If you want to use a "post pour" treatment for extra protection then do it.

A good densifier with a waterproofing agent sprayed post pour will help retard the evaporation and help with cracking. It will also slow water migration from the top down (spills).

Good luck.

 

[pauls340]

First I should say I agree with many of the things being said here but this forum opens up a chance for a number of us salesreps to steer people toward "our" systems. Unfortunately for me I did not have Vapor Lock available three years ago to use VL20/20 admixture. THAT is the best way to go. It uses those 17 gal of free water and changes it to additional CSH gel, along the way to vapor proofing your slab, it waterproofs it. I used a penetrating product VL0/0. So flooring has certainly been installed for many years and you have to take some steps to properly prepare your concrete Step 1 is to test the concrete. A petri dish filled with calcium chloride, it’s in the salt family, is a good test. You take that dish, weight it, put the cover over it and moisture vapor emission comes up in there, you then weigh it again and it will weigh more. You then apply a complicated formula to determine how many lbs of moisture/ 1000 sqft you’re taking in. The problem with this test it only looks at the top ¼” to ½” of the concrete, it doesn’t see all that Free Water hanging out at a lower level. So a second test was devised, it’s call InSitu Relative Humidity Testing, you drill a hole down into the slab, about 40% of the thickness, you put this unit in, hook it up to a computer-gizzmo that sends out a signal and the time it takes to get back is a measurement of what it perceives the Relative Humidity to be. And together, these two tests are a reasonable indication whether your slab is too damp or OK to install your flooring. So if you pass these tests, the next step is to install the flooring. Our presentation was done for a large Architectural Firm in Boston which does nothing but Healthcare work, what they told us in the last 4 years, 100% of their slabs have failed these two moisture tests. And they are working with the highest level of moisture sensitive materials in the Healthcare field. So what they do is topically treat those slabs. They put it in the Construction schedule in the front end and they don’t even bother to test the slabs they just treat them. And they just did that to the ½ million square foot Yale Cancer Ctr in Conneticut , and in the process of doing that they spent $2.5 million. So I want to run thru the process real briefly to show you how they topically treat their floors. But remember this process was created as an evolutionary solution and its proven to work and is still the gold standard to stop any moisture from coming thru and ruin any flooring.The first step is to shot-blast with one of these expensive machines and the BB’s leave a bondable texture on the surface. You need that texture in order to put an Epoxy coating on next. This epoxy slows down the rate at which the moisture vapor emission of the Free Water comes out of the concrete. It doesn’t stop it , it just slows it down to a tolerable rate. Since adhesives won’t stick to epoxy you need to then install a self leveling cementitious product. You can then install your flooring. So part of the point of this story is this Firm does this on 100% of their jobs so they can run a tighter construction schedule. And your looking at $5 to $10 / sqft to do that. ALSO, our first and second Permeability Test came back which forces a drop of water at 15 times static water pressure into a 4" core of concrete. Both their results show it would take 6,319 years for a single drop to go thru a Vapor Lock inhanced concrete slab. So, bottom line, in my best professional opinion, if I have the chance to insist on using VL20/20 as an admix, I would. My second option would be, and was to use VL0/0. Your decision is not an easy one based on all of our info, good luck

 

[pauls340]

Just curious, how much does a visqueen vapor barrier cost? About?

 

[Dustin Crawford]

Thank you for all the information.

I really do not know much about the subject. But here is where I am at and here is what I do know.

This will be a 6" slab with rebar. I am not trying to make this the best thing ever because we are on a budget but I am trying to make my money go towards areas that really require it.

I know people who have no barrier. Some use plastic sheeting. Some use sand.

Due to my grade sand is not an issue but my base is very free draining and it is 18" deep. With that being said the shop is built in a valley basin that has no drainage at all (sea level) so in the winter (wa so think rain) the ground is VERY wet. The ground percolates really good, but it can rain faster than it drains if it keeps going for days and days.

So with that being said, I just thought it might be smart to really think about a vapor barrier. I have never experienced a slab that wicked water so I dont really know if it is a real problem. I just know I dont want it to be.

So I am just looking for recommendations because unfortunately, you dont know what you dont know.

In my mind I love the idea of doing a nice overly thick plastic sheeting. I have no idea on price though. I also like the idea of an ad mix. But again dont know price and really dont know if this is a problem I should devote much mental effort to.

DC

 

[pauls340]

admix to the concrete will not add more the 45cents per sq ft, I know that. If it fits in yur budget, do the plastic also. Plastic VB will not affect Vapor Lock. Anywhere on the globe, even the desert, you will achive 100% RH under a slab of concrete. In 1999 when the EPA first began to reduce the voc levels in surface coatings, a $5billion industry started in repairing damaged floors. With ALL this said, no matter how hard you make your concrete, if Mother Nature wants to move it, She will. I poured a 5" monolithic floor and rat wall, with fibre mesh and steel mesh and four months after my pour I had a 15' long hair-line crack goodluck

 

[mypov]

The problem with vapor barriers is they do absolutly nothing to or for the free water in the concrete. On a 4" thick slab there is about 32 gallons of water in a cubic yard (81 sq ft) of concrete. Of the 32 gallons approx. 15 gal is used to "make" the concrete leaving approx. 17 gal of free water to cause all sorts of problems. I didn't spend a penny on a vb, I applied Vapor Lock which uses that 17 gal to make additional CSH Gel. Three years later, zero moisture from day one, any paper, wood, or steel you pickup off that floor, it is 100% dry. Google Vapor Lock, good luck

that stuff sounds awesome! Never heard of it - how much is it and how do you apply?

- sorry to steel thread, but this sounds like the stuff to use...In theory though if you put vapour (canadian) on the ground before the pour shouldn't the "free" water dry through the concrete eventually? Have done many pours using 2"foam insulation, then VB (6/10ml poly), then RB then concrete and havn't had a problem.

anyway, best of luck, lots of ways to skin a moose!

If you are worried about water you might think about putting in a sump pump, or a weeping system. Definitely NEED the VB if your ground is wet the concrete is guarenteed to wick moisture - MAKE SURE YOU INSTALL SILL GASKETS as well on your bottom sils - you should also use PWF for the wood touching concrete (wood should never touch concrete)

 

[pauls340]

The old addadge that concrete cures in 28 is totally false. Un-doctored concrete, inside a building evaporates 1" / 40 days but there is not a single construction schedule that will allow that. FYI, the Canadian plant for VL is in Smithville, SE of toronto. You can get it from Form & Build's five locations.

 

[Edger]

Here are links to two more products that waterproof the concrete all the way through. No surface sealant or product to stop epoxy from adhering. So easy, just spray on top of damp concrete and let it penetrate. Creates a gel inside the concrete that allows air molecules to pass through, but not water molecules.

I used Aquron many times on slabs and epoxy always adhered well, never any moisture problems afterward.

http://www.aquron.com/our-products/concrete-protection-and-waterproofing/aquron-cpt-2000/
http://www.protecrete.com/Densifier.htm

If I was polishing concrete I do not think I would use either of these as a densifier, but they claim that they densify concrete which I am sure is correct, but the two densifiers - one for concrete polishing and the above for water proofing are not the same and should not be confused.

A densifier for concrete polishing hardens the top to allow for a higher level of gloss, the waterproofing densifiers add density to the whole slab via their gel process. So without any technical proof I would guess that the surface hardeners would not waterproof very well and that the waterproofing densifiers above would not harden the surface enough for concrete polishing.

 

[LegacyIndustrial]

Edger:

Good morning. It is morning in AU? We have had good luck with the middle ground. Our HD-7939 seems to hold back water pretty well and densifiy as good as our other products. It too forms a gel in the gaps.

 

[ConCretin]

So with that being said, I just thought it might be smart to really think about a vapor barrier. I have never experienced a slab that wicked water so I dont really know if it is a real problem. I just know I dont want it to be.

Dustin, a lot has been covered in this thread and it's all good info but I want to clarify a couple things to help you digest it all and make a good decision.

A membrane vapor barrier such as 6 mil poly or Stegowrap are designed to stop the movement of water vapor though your slab. This method is by far the most common and is pretty much standard practice.

However, membrane vapor barriers won't help much if you have drainage issues nor will they address residual mix water in the concrete.

Drainage issues must be addressed with site grading or under drains and are priority one. You have to get this right.

Residual mix water is generally only relevant if you intend to apply flooring. You will need to wait out the drying process or apply a topical sealer as has been mentioned.

Finally, you've mentioned sand a couple times as type of vapor barrier. It isn't. Sand can be used for a number of purposes under a slab but blocking water vapor isn't one of them.

At this point in your construction, the important decision is whether or not to use a vapor barrier. Since you can't do it later, you should go ahead and put one in.

In my opinion, your priorities should be setting your grade to allow for drainage, a well compacted granular base, a vapor barrier, properly supported steel reinforcement, controlling concrete slump and well planned control joints. Get these right and you will be 99% there.

Hope this helps.