Vapor barrier in crawl space..HELP!?

Question

We were told that moisture levels in our crawl space were 3% higher than usual, and were told to replace our vapor barrier among other things. Since we have to seriously consider the $5000 investment this person told us, we thought of going with the most affordable. FYI: It has been a very rainy season this year after 3 years of drought.

So, where does one buy a vapor barrier? I've looked everywhere online and I can only see long explanations as to what it is but no information about where to buy one. And I wasn't looking for aluminum foil, plastic sheets, or kraft paper. Is there a real thing?

Answer 1

the vapor barrier is the poly that is on the floor of the crawl space.  IF you already have poly on the floor, what good will it do to replace it.  I wouldn't touch it.  The most I would do is put an exhaust fan in the crawl space.  I lived in Indiana once and was astounded by the people that lived over puddles/lakes of water and you're worried about a measly 3 %.  In Indiana under our house it was always like after a rain storm, puddles of water.  Try the fan.  I've installed fans under houses up here in Maryland for that very purpose.

Answer 2

mmmm,interesting

From my stranger than fiction files.In my area the builders and restoration companies are starting to pour concrete.If the house is already built the bring in a small trailer pump and put down a 2" - 3" of concrete over plastic.

It may sound strange but a reality here,still way less than $5k.

Good Luck

PS: Here is what a google on vapor barriers revealed,some good info.

Answer 3

5K??? Go to your local hardware store and tell them what you want to do.  If it's just the vapor barrier, it's that layer of plastic sheeting that's on the ground and you simply need to replace it ($50).   If it needs additional work, you may need stone (crushed) to put under the barrier.  The idea is to create a vapor, or moisture barrier between the ground and the house.

Answer 4

A vapor barrier is just a plastic sheet that goes over the studs then the sheetrock is installed after the vapor barrier is put in

It comes in a big plastic roll

Answer 5

Go down to your local lumber yard and ask for it.  They will have it or if they don't, they will be able to order it in for you.  You'll have to know how much of it you'll need.  What you'll be looking for is a 6 mil polyethylene vapor barrier.  There are other ventilation products out there that can also help to keep the moisture levels down.  You might consider a powered crawl space ventillator.  It's basically a vent at the perimeter of the crawl space with a motorized fan that helps to circulate air. through the space.

Answer 6

Sounds like you've got more going on than just a slightly higher humidity level in the crawl space.....

A common vapor barrier is just a layer of plastic which prevents moisture from traveling thru it.  6 mil plastic works just fine, and can be found at any hardware store.  Seal or overlap the joints (by about a foot), and penetrations.

There are products made for cases where you want a stiffer plastic membrane, like when you are pouring a concrete floor, or foundation/wall.  One such product is called "Plenom".  This product is NOT needed over a typical crawlspace floor.... this is what you would put UNDER the concrete BEFORE it is poured.  

There are some other considerations here too.... do you have a central air drain, or clothes dryer vent that run into the crawlspace?  If so, running those to the oustide of the crawlspace will help quite a bit.  You'd be surprised how much moisture is created by just those two.

Cross ventilation is also important to prevent moisture build up.

Feel free to email me, with details, and perhaps I can offer some more specific advice.

Good Luck

Answer 7

Run as far away from this guy as possible!

3% higher than usual? What is "usual"? +/- 3% is not a huge swing in the humidity level in a conditioned space (I am assuming your crawl is "non-conditioned" space"), let alone a non-conditioned space like a crawl space.

The current versions of the IRC (the ones that I know that are currently enforced in my State - we don't have a state-wide Code) require a 6-mil poly vapor retarder (there is nothing that really completely blocks water vapor, other than an expensive, spray applied coating (and I'm not sure that any I've seen meet the Code requirements for "Smoke Developed" and "Flame Spread Rating" that would allow them to be installed without some type of fire-rated barrier over the top of them). No need to shop on-line, this is one item that I buy at my local home center. (One of the few products I will but at a home center.)

Make sure your crawl space is properly ventilated [one square foot of ventilation per every 150 square feet of crawl space - with one vent within 3 feet of each corner (2003 International Residential Code Section R408.1 & R408.2)]; then unfold and unroll the poly vapor retarder out across the floor. Cut slices where needed to get around any columns or posts. You may want to fill any low spots with pea gravel, first.

Overlap the joints a foot or two, then, using "House-Wrap Tape" (NOT DUCT TAPE), tape the joints shut. You can even run it up the walls and staple it to the sill plate if you want. [House-Wrap is any of the “Tyvek” type products available; the tape made for these products withstands moisture better than any tape around.]

Unless your crawlspace has an extremely low "ceiling", you and another person should be able to get this finished in one or two hours. Use some of the $4, 940.00 you save to buy some good knee pads, and a little more to get a good back massage when you're done. Maybe a few more bucks to buy a pair of steel-toed boots to kick the shyster off of your front porch with, if he shows up again trying to sell you the Brooklyn Bridge!

**************************************...

What "Just Me" is referring to is called a "slush coat" finish around here. Our State Plumbing Code requires that any slush coat in a crawl space be pitched toward a properly vented floor drain. When necessary, the floor drain needs to be run to an ejector pump in a sealed pit, or protected from sewer back-ups by a "back-water valve".

A slush coat over a vapor retarder will cut way down on moisture AND dust.