Vapor Barrier Under Slab

fixitpete

I'm doing a job that requires a super-quality vapor barrier between grade and the slab. Slab is 4" think (rat slab) in an ultra-high moisture area.

Any suggestions on materials? I'm looking at VaporBlock by Raven, but I'm interested in feed back etc. as to what the latest and greatest is that won't degrade, etc. over time.

Thanks!

Chris Johnson

10 mil poly does the job

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Chris

fixitpete

You're talking about just regular poly?

I'm looking @ ASTM E 1993 - 98, which you can see another example of here: http://www.wrmeadows.com/vaporbarriers.html

Thanks.

concretemasonry

Who says it has to be a super-quality vapor barrier? Are there specifications?

If you decide what to use with no specifications or guidance.approval from the owner, you are responsible.

The ASTM E1993 is a ten yrat old specification. There is also a ASTM specification for mil poly whether it is 6, 10 or 20 mil thickness.

If there are no specifications, tell the owner what you options you can use to use and give him the prices according to the materials used. Then he can choose how important it is to him.

If you buy a special film, you could be faced with a minimum purchase and have to install it to avoid losing the warantee.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

denick

Fixitpete,

It seems you are looking for something like "moistop" by Fortifiber. www.fortifiber.com/concrete.html take a look at their site. We have used this product and have never had any problems.

You are looking for a "vapor barrier" which stops the transmission of water "vapor through a slab? Your not looking for a "waterproofing" because of a potential problem?

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Nick

"Every day I remind myself that my inner and outer life are based on the labors of other men, living and dead, and that I must exert myself in order to give in the same measure as I have received and am still receiving" Albert Einstein

fixitpete

concretemasonry... as far as specs, I'm looking for the best method to utilize for the application. A very high water table in an extreme coastal area crawl space where a 3"-4" rat slab is being installed. The major concern is moisture entering the home, specifically the ground level -- where hardwood floors are being installed.

If the 1745 will meet the needs, that's great... however I was under the impression that 1993 is more stringent. If you're thinking that fortifiber's materials will do the trick -- I'll look into it. I just need to allow as little moisture into the living space as possible. The plan is as follows:

I really appreciate your input on this. I've consulted with several concrete and moisture abatement people that I've dealt with over the years and it seems that as long as we conform (somewhat) to ASTM 1993 and add a surface pump we will significantly reduce the moisture in the crawl space, allowing for installation of the material that we're after.


Basically, the plan is as follows:


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Grade soil toward the lowest point, in this example, toward one corner. The thinnest section of slab shall be 3" --

Next a vapor barrier that conforms to ASTM1993 (WR Meadows or Bituthene (I *THINK* "System 4000" conforms)(?)

at the low point we're going to J-Bolt a starboard (heavy plastic) material that will receive a surface mounted submersible pump. This pump will only run when water accumulates from flowing off slab, or during a flood (during a flood, it won't stop until water recedes or water is vacated.)

Pour slab.

Done.

This -- In combination with Aquabar-B (under hardwood install) (just because) -- should provide an exceptionally good substrate and environment for our materials.

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The vapor barrier is what I'm hear to brainstorm over and determine the best one for my needs.

The barrier is block moisture from permiating through the slab, not for waterproofing.

Thanks for all the help folks I appreciate it much.

Chris Johnson

With what you just described a weeping tile system under the rat slab is a given, without all the specs available I would be hesitant to guess on exactly what you need but more or less it should consist of a perimeter drain on the inside with several pipes running across the middle of the area to pick up any underslab water and deliver it to the sump pit, all this pipe should be covered in flter cloth and specified amount of clean gravel put in followed by the vapor barrier (which by doing this will stop moisture from working it's way through the slab) than your rat slab. I would even be tempted to install some floor drains on a seperate line through out the area just in case of a water issue arises.

Is this expensive? Yes, but in comparison to future water issues it's a lot cheaper.

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Chris

fixitpete

Sump pit, pipes below grade, etc. are all not possible nor usable since the water table is so high. Water table is 18" below grade and crawl is already 6" below grade (leaving 12") -- add to that the combination of frequent coastal (tidal) flooding and high tides, and the sump and pipes would always (or almost always) be under water.

Anything done to drive the water away has to be done @ grade or slightly below grade, and anything that pools @ grade (on slab) has to be driven away by gravity and pumped away.

Most people just do a rat slab with some junk 6mil. poly... I'm looking to do it just a little bit better and not have a problem with decomposition of the barrier and the surface pump with grading to keep things dry after flood water recedes.

Chris Johnson

Silly suggestion here...lift the house another 8-12" help alleviate the known issues.

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Chris

fixitpete

That would be very nice... but not feasible for this application.

Hoven

If your going to use poly I would use the thicker mil. The stuff tends to break down when in contact with concrete over time. I just recently jack hammered out an older poly floor maybe 12 to 15 years old. The poly was in tatters and weak. If you do use it I would cover it with dirt at least to minimize contact. Not sure what does it but I would venture a guess that its the lime. The other products mentioned sound far superior.

Griffino

I'm with Chris, lift the house

One thing I'll add, most slabs' surfaces I've seen failed are from the vapor retarder/barrier ability to push the mosture of curing concrete's water content through the top severely weakening it. They often are flaking. In most cases of a flaked concrete slab, you and look under it and find the culprit is one of 3 things; over working the surface while still very wet, over vibrating, or the mentioned senario above. To overcome this, use additives to lessen the amount of water needed to pour and go with a low slump concrete.

jomama

How about just raising the concrete floor 6-12"? The only downside would be clearance when servicing mechanicals, which should be minimal.

scrapecc

Sounds like trouble to me. you can try to seal it up, but hydrolic pressure will likely push by any barrier at the edges of the floor. you may want to compare this to a tunnel under water, they build 2 chambers, one they pump water out of, and the other cars drive through. you have to come up with a way to keep water away from the floor. I dont think a barrier is going to solve your problem.

Rickle

... Wow Totally misread what you were saying.

scrapecc

Whoops, missed a part there. don't i feel like an idiot. anyway, I just did a slab at a new mall, plus some remove and replace for plumbers. It was just a simple 10 mil poly, I would think that would work fine.

Big Dog Dan

On the subject of moisture control and vapor barrier, can anyone give some advice on this disaster?

I was called in to rebuild walls and wallboard that were removed because of a leek in the basement.
Floor is concrete,within 20" of water table, sand under concrete,no barrier.
After pulling up the carpet the pad was all wet,damp and actually holding water in places. The floor had 5 long cracks in 5 directions all across the floor.
I jack hammered through the floor to find no barrier and approx 20" of sand.
There is no concrete sealer applied.
The house is built with so much glass that the temperature on the 2nd floor is usually 30 degrees hotter than the basement.
I believe it is actually acting like a wick in a kerosene lamp-the heat is pulling water through the basement floor continuously. The dehumidifier fills in 2 hours and is likely just helping pull more moisture through the concrete.
The hardwood floors upstairs are all warped, and the wallboard in the basement is molded slightly. House is 12 years old.

I need an answer before I bring the carpet guys back.
The whole house was a quick build as far as I am concerned. Walls are still moving and cracking the finished paint and compound.
Can I seal the concrete?
Thanks for any advice

lukachuki

why don't you ask in your own thread...makes it simpler and less confusing.

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Big Dog Dan

Yes I was thinking of that, but I also thought I should check to see if others were already talking in the subject area,it would be a good place to ask.
Thanks

cdkyle

WOW, what a delay in time. This thread is like a time warp. 12/08, then picked up again in 7/2011. Anyone ever think of checking the dates before posting? mmmmmmmm.

Anyways, I friggin hate pouring on poly. I have never had good results. I hate the crap. Most 10 mil here = Stego, tape the joints, etc. What a pain in my arse. But worst of all, I personally feel this is a severe detriment to the hydration process of the slab during the actual pour and finishing, therefore producing an inferior product. I've just had too many bad experiences pouring on poly. With a real windy day, the floor will dry too quickly on top, but still be too wet on the underneath side to finish properly. My suggestion will always be to eliminate the poly, add a water repellant to the concrete, and pour away. Do not be confused by a so-called expert (architect) telling you to use poly. Its a Bad idea, unless of course your building below sea level. Then, either way, your SOL. IMO