watchtower7

I am buying a house with exposed dirt flooring in the crawl space, the inspector recommended 6ml plastic.
I am an idiot, put it on the dirt or staple to the flooring joists?

inspectorD

Put it on the dirt. Stapling it to the floor joist is to close to being a vapor barrier on the wrong side.
We usually run it up the concrete wall a bit and seal it with a nailed board attached to the concrete, and silicone between that. Leave your vents open in summer,closed in winter.

It is a bit of work to do...but saves your house in the long run from the moisture.

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CyFree

I'd strongly recommend that you to get a specialist on the case, some will give you a free consultation, so you loose nothing to have one take a look and give you an estimate.

If you are a DIYer, get the best how-to information available on crawl space encapsulation from trusted sources.

You will eventually find a lot of controversy around closed vs. vented crawlspaces.

I am personally in favor of sealed, lined, properly drained and conditioned crawlspaces, as recommended by independent studies such as the ones conducted by Advanced Energy.

But take a look at what the building code in your areas has to say about it, make an informed decision.

This is the kind of job that, if not done properly will aggravate moisture problems, rot the floor joists by allowing mold to breed in. So the better you do it now, the less worries you'll have in the future. It is a good investment on your newly acquired property.

joecaption

I get to go under houses almost every day. Any home I've seen that someone tryed to "seal" it up has fungus growing. Most have not had the dehumifier checked in years or were just draining into a trench.
All the ones I've seen with automatic opening foundation vents every 10 ft. and black 6 mil. plastic on the ground were fine.
90% or moisture in a crawl space should be addressed outside not inside.
Working gutters. No mulch piled up againt the foundation. Grade running away from the house. Grade under the house higher then the grade outside.

inspectorD

All kinds of things go wrong in crawlspaces, and each home is a little different.
What works in VA, may not work well in CT, or Maine with freezing pipes, always consult a professional for your area.
There is no one answer.

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itsreallyconc

hopefully the other responders will agree with this, too,,, don't waste time buying 6mil plastic,,, its only good for the 1st time someone crawls on it,,, get, at least, a layered vapor barrier,,, stego is 1 brand we use altho normally we pick up 20mm 7layer stuff.