On Sat, 20 Sep 2008 16:49:31 -0700 (PDT), wrldruler
wrote:

Converting 300 sq ft garage into family room. Installing full floor
above garage concrete slab. I want to put a polyethylene vapor barrier
on the concrete.

Most places I read recommend 6 mil polyethylene. Home Depot selling
for $50.

When cleaning out the garage I found a brand new box of 4 mil
polyethylene that my Dad had given me.

Would it be a problem if I used the 4 mil that I have, instead of
buying 6 mil?

I have a giant box. Can I double-up the 4 mil, creating a 8 mil
barrier?

Thanks,

Chris

Hi Chris,

Polyethylene is an extraordinary VB.

(I won't bore you with the details, but I use .1 mil for
certain purposes, and it does the job.)

So, in your situation, the issue is fragility rather than
the thickness needed to provide a barrier to the migration
of moisture.

I would say "yes," you could use the 4 mil (and be careful
to avoid tearing it.) Or, double it, and sleep a bit better.

All the best,
--
Kenneth

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