How to install vapor barrier in crawl space?

Question

Is there anything special I need to do...or just put down plastic...does it need to be secured to anything? If so, how. And is there a special product to use? Or just any old plastic will do? I have a 2/3 basement, 1/3 crawl space and currently there isn't anything in the crawl space but dirt. Thanks for your help!

Answer 1

national building code requires "6 mil poly" on vapor barriers......just spread it out, lap it 8"-12" , they make "U" pins that u can push into the ground to hold it in place.....u need t stay back from the edges of the foundation 12" to allow for some moisture to escape from the ground( per my insulation guy).....

is sold in many widths and lengths............

lic. gen. contractor

Answer 2

Visqueen Vapor Barrier

Answer 3

You can simply spread it out over the dirt. I would overlap any seams by a foot or so and weight it down with rocks or bricks; there may be animals that get in and you don't want them moving the plastic all over the place. You could use anything since it is not exposed to ultraviolet, but I would get the heavier 3-mil type commonly used for painter's dropcloths.

Answer 4

The most popular and economical product people use is 6 mil plastic sheathing which contractor's usually refer to as "Visqueen" . Visqueen is a name brand that was very popular and pretty much out-sold all other brands in use during it's time. (It's like peope asking for a Kleenx instean of a tissue). Anyway Visqueen and it's competing contemporaries products were/used to be made of pure /. virgin polyethelyene. Usually you purchae a roll that is 25' wide and 100 feet long for about $ 75.00 - $ 99.00, (prices vary).

"Pure" polyethelyne sheathing was available in difering mil thicknesses starting at 2 mils for commercial use, and then going up in 2 mil thicknesses to 10 mils. After that It is usually reinforced with string or polyethelyene fiber string, in a "sandwich" configuration, usually starting a about 25 mils.

Virgin Polyethelyne, (now theres a funny notion - a man made chemical developed from petroleum based polymers is called "virgin" isn't the term "virgin" reserved for pure & naturally occuring things in nature?). And the answer to that two part question is "yes" and "no" . "Yes" the term "Virgin" is reserved for pure pruducts, and "No" the product does not have to be "Naturally" occuring. Think about it - we "Introduce" crops and animal life into areas where that grain crop or fish, or animal species has never been before - where "Nature" has never intended it to be. But Man decides to grow Corn and Wheat in the Desert - and with irrigation does so. Man decides to grow Nile Tilapia in Fish Farms in Mississipi, and does so with wild Success.

Ah, but there is a price to be paid for the success of polyethelyne as a "pure" vapor barrier material with a great perm rating of about .3. Which is a fantastic perm rating. That is almost "water proof". (Please note that there is only one truly "watrer proof plastic sheeting out there - and it is called by it's consumer name of "Saran Wrap" . Saran Wrap is the base line material, it has a perm rating of 0.0

Along comes the Great Oil crisis of the 70's. the energy crisis of the 80's to follow on the heels of that, and in the 90's the enviromentalists finally get people and the Government to wake up to the idea that we can and are killing the planet we live on, and if we do not become good steward's and Global Citizens, we might just succed in killing the old Girl and our-selves right along with her.

And now the irony of using polyethelyne as a Vapor Barrier comes home to roost. In the late 80's and early 90's we most of us strarted to recycle. Clear plastic in this bin, green and brown glass in this bin, white paper in this bin, cardboard only in this container, aluminum only in this container, unruly children only in this soundproof bin, - and so on. And What happened? The Maker's of Visqueen were approached by the Recycling industry who now had all of this recycled plastic to get rid of, and said "Hey" if you melt this clear stuf down and add it to the mix with your new stuff wont' that work? it's the same stuff, - you will just be "recycling your own product, and you can in effect, for very little cost, keep selling some of your procduct line over and over again at a profit. Wow! What a deal! The Problem is that the use of re-cycled plastic - while well intentioned introducted contaminates and other filler chemicals into the mix, and the polyethelne sheeting was not uniformly pure anymoremore insome places in the sheet there were areas whixh were, and areas which were not, but you really could'nt tell by lookibg t the sheet whixh areas were or were not. so when you by plastic sheeting today, (Plastic polyethelyene sheeting), the perm rating could be anywahere from o.0.3 to +.10, so some manufacturers will just split the difference and average the test results and declare the sheeting to have an average perm rating ot .06. Which is not good enough to install sheet vinyl, linoleum, or even some carpets over if that were the moisture content of the S.O.G.

However, the Industry has seen the Problem and responded to it. There are now several companies out there that make Vapor Barrier systems, a couple are Stego Industries, and Raven Industries. They both make 15 and 20 mil VB sheet and tape systems that have very low per raings, and sheet goods that are almost impossible to teat, rip or puncture. You simply roll out the material, tape it to the perimeter walls, tape it around any penetrations through the sheet, like a plumbin vent or radon tube, and tape a lap edges where shets over lap. JUst follow the instructions, and you will habe a complete seal over the crawl space in short order. I recommend that you spend a little more and get the 20 Mil system, as opposed to the 15 mil system. - As a former specifications writer, I an much more comfortable wih the slightly heaver system. I would by the materials from a local Commercial Earthwork Contractor in your area, rather than a Contractors supply house, only because you don't need much material, - I suspect less that 500 , and I think the smallest rolls that these products come in are probably double that - or more. Remember that you need to get the pressure sensative tape to do the job as well, and there again, you probably wont;t need more than 2 rolls to finish the job, (as the Contractor).

One thing you can do is call the Stego or Raven rep in you area or look them up on the interNet, and get the info you need, including local supply outlet, and contractor contacts. Who knows, you may be able to get what you need right from the salesman. Good luck.

I'm pulling for you.





The catch is that recycling has all but ruined the