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Polyethylene quality and characteristics

Hi. I have come across various qualities of polyethylene for use under my slab. The prices vary considerably; from ~$120 to $280 for 10 mil 20'x100'. I have been told that thickness being equal, some brands will degrade in a very short period of time (matter of years), as well as off-gas significantly more. They claim that the type that is "agricultural/construction film" are cheap and not intended for under slab use. Is there truth to this, and should I shell out 65-75% more money for the "better" grade plastic? Thanks in advance.

Asked by Matthew Michaud
Posted May 14, 2014 12:11 PM ET
Edited May 14, 2014 12:51 PM ET


2 Answers

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As far as I know, the main reason that polyethylene degrades is UV exposure (sunlight).

Keep the polyethylene in the shade. Once it is covered with concrete, it should be fine. I have used 6 mil poly for the purpose, and I sleep well at night.

Answered by Martin Holladay, GBA Advisor
Posted May 14, 2014 12:55 PM ET
Edited May 14, 2014 1:15 PM ET.


I have used boat shrink wrap which is darn good stuff just because I had some. I also laid generic black 6 mil on wet dirt in a crawlspace twenty years ago, was on it just this last month crawling about and it is like the day I installed it.

Answered by aj builder, Upstate NY Zone 6a
Posted May 15, 2014 10:34 AM ET

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