At what stage in the construction process should the plastic be put
down. This is a single fam.
residence. House is dried in, (except for a front door) and the
insulation guy wants to wait but it's very humid under there (located
in Central alabama) and some joists look moldy. I've read on some
sites that say ASAP and others to wait longer. Any thoughts?
I'm a builder in Birmingham, and I have my framers put the vapor barrier
down on their first day. That way no one has to crawl around to install it,
and I can be sure no framing lumber gets left under it for termite bait.
It doesn't have to go in at that time, however.
If you have hardwood floors going in, its best to have the vapor barrier in
a few weeks before that installation as the moisture can affect its
You should have at least 24" from the ground to the bottom of your floor
joist, and 18" from the ground to any girders.
It is likely that the mold came on the joist as they have a lot of moisture
in them and they have been sitting on a lumber yard or in a warehouse for a
ASP Home Building, Inc.
on 9/24/2007 9:44 PM email@example.com said the following:
Are there any vents in the crawl space?
There should be, to prevent rot and mildew, which apparently has already
If there are vents, perhaps using a fan blowing into the space until the
vapor barrier is put down will help.
On Sep 24, 9:44 pm, firstname.lastname@example.org wrote:
Check the moisture in the ground, the amount of vent area, then visit
The Building Science Corporation web site.
My preferance, assuming adequate venting and no unusual levels of soil
moisture, would be to put down 6 mil or better poly with edges lapped
and fastened to the masonry NOW. Cover it with a couple of inches of
sand and hope the insulator doesn't make a mess of it. The Habitat
for Humanity houses I've designed put down the poly early with good
results over 10 years.
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