Even though it's only 3 mil, it would probably work fine, but I agree
with Trader that it'll be harder to work with because it'll be easily
Whatever you do, DON'T use two layers of 3 mil plastic to make a 6 mil
vapour barrier. If water ever gets between those two sheets (from a
flood, or whatever) it'll never dry out and it'll be a breeding ground
The building code here in Canada requires 6 mil polyethylene plastic for
But, the truth is that when companies make this plastic, it's thickness
can vary. So, if you buy plastic that claims it's 6 mil, that means
that the thinnest area in the roll is guaranteed to be 6 mil or more.
You'd be better off just buying something labeled as "vapour barrier",
in which case it's probably about 6 mil on average. The stuff that's
guaranteed to be at least 6 mil at it's thinnest point costs a lot more
than something that just claims to be "vapour barrier".