What thickness plastic to cover ground in crawl space?

Question

I need to put a new covering of plastic down to cover a small (<150 sq. ft) crawl space. The home is in Massachusetts.

What thickness should I use? I was thinking 6 mm.

Answer 1

6 mil plastic should be fine. While you are underneath, check for loose insulation and spider nests.

Answer 2

From Wisconsin: 3 mil or 6 mil plastic will work, the 6 mil might be hard to find in rolls large enough, 6 is thicker and would be better. Here we typically put down the 3/6 mil and cover it with 3/4" wash stone. Someone above mentioned pouring a thin layer of concrete; yes this would be wonderful and I have seen it done but generally is not done due to the added cost. I would rather see the inside of the crawlspace walls insulated (styrofoam) and the plastic (& wash stone) on the ground. This can assist in any radon concerns and if you ever have to work in there it gives a clean floor to be on. As long as the sidewalls are insulated I would prefer not to insulate the underside of the floor, any leakage from above is going to create a real mess and potential for mold. Probably one of the biggest things for a crawlspace no one touched on is ventialtion. If you do not have side vents for the crawlspace I would closely monitor the moisture levels down there for a year on a monthly basis, any signs of mildew/organic growth start to develop and I would add vents. Usually older homes are not as tight and naturally breathe, we are starting to see more issues on newer homes due to be almost to tight.

Answer 3

With all due respect; I'd be more inclined to attach vapor barrier to the underside of the dwelling, and perhaps not need it at ground level. Certainly adding both might offer you some comfort zone, even if virtual.

6 MM is like yard trash bag weight; but depending on the substance might be adequate?

Without knowing at all your purpose or intent or the conditions that direct your intent; I suspect all the answers will be personal opinions or experiential from anyone living in MASS.? Under and directly attached to a structure I'd probably still use greater than 6 mil,,,and at ground level something that would endure over the long term no matter the thickness.

Steven Wolf

Answer 4

6 MIL will work. Make sure you seal any joints (and overlap). You can run it up the wall a ways and tape it off also. When using a vapor barrier, it goes on the "warm" side of the wall or joists. Think about how fiberglass insulation with vapor barrier is installed. Securing it to the bottom of the floor joists would cause more problems than it solves. My current house had this done and I had water dripping from the plastic into the crawlspace.

Answer 5

First of all, don't cover the ground with plastic! It will not allow the moisture to escape into the ground, and you will develop mold and mildew. Instead, cover the ground with landscaper's cloth. this inhibits weed growth and allows the ground to absorb moisture.

PLastic should be applied to the WARM side of your crawl space. Wrap your floor joists, subfloor, and exposed sill plate with 6 mil plastic. Next, install your insulation. Use 1 x 2's to retain the insulation. It's a lot of work, but you will not have any moisture or mold problems later on!!

Answer 6

Closing the crawl space vents during the cold days will help save the water from freezing inside the pipes that usually run through the crawl space. It also helps in keeping the crawl space at a higher temperature that in turn may keep the floor of your house slightly warmer than it had been otherwise.

Answer 7

First off, it's NOT 6mm. it's 6 mil...looks like millimeter, but isn't. 6mm would be 1/4" and that doesn't exist. Likely as not, you're using it as a radon barrier; landscaper's cloth would be of no use for that particular application.

However, if possible, lay down a 2" thick re-barred concrete pour instead.

Answer 8

what to cover crawl space plastic with

Answer 9

if covered like that,it will help moisture buildup and then termites