Is it normal for this vapor barrier to be this see-through?

You’re looking at a major red flag beacuse that sounds like 1-mil or 2-mil painter’s plastic, wich has no business being behind a permanent wall. For a proper **vapor retarder** in a basement, the industry standard is 6-mil polyethylene. Anything thinner is basicly a disposable drop cloth and will tear the second a screw head or a piece of rough lumber brushes against it during the rest of the framing and electrical install.

That "better than nothing" excuse from the contractor is total nonsense. Using the cheap stuff is a classic way for a lazy crew to save fifty bucks while compromising the whole project. It’s a complete false economy. If you can see your hand clearly through it, it's not thick enugh to act as a reliable barrier against the humidity common in concrete foundations. Once those studs are covered with drywall, you’ll never know if that plastic shredded or pulled away from the staples, leaving your insulation and framing vulnerable to mold and rot.

It's also about the durability over the long haul. Thinner plastic is far more likely to degrade or puncture under the slight movements of a house settling or even just the air pressure changes in the wall cavity. You shoud absolutely insist on **6-mil poly** at a minimum. It’s significantly tougher, harder to puncture, and acutally meets building code requirements in most jurisdictions for vapor control. If it feels like a grocery bag, it isn't the right material for a foundation wall. And honestly, if they’re cutting corners on something as cheap as plastic sheeting, you need to watch how they’re sealing the seams. A barrier is only as good as the **taped overlaps**. If they just slapped it up with a few staples and left gaps, the thickness of the plastic won't even matter because the moisture will just move right around the sheets. Don't let them move forward untill they swap it out for the heavy-duty stuff.

Totally agree, that thin stuff is a joke. Just to add to the previous point, make sure they're acutally using a bead of acoustic sealant along the top and bottom plates too. Most guys just staple it and call it a day, but without that non-hardening 'black death' caulk, even 6-mil won't create a true seal. If they’re cheaping out on the plastic, they’re definitely skipping the sealant, which basicly defeats the purpose of the barrier since air will just cycle moisture right behind the studs at the floor level.

I'm such a newbie at this, I didn't realize the thickness mattered that much! If the plastic is that thin, does it actually cause the wood studs to rot faster? I'm also wondering, does that 6-mil plastic need to wrap under the bottom of the wood where it touches the concrete floor, or just stay on the wall? My contractor just has it hanging like a curtain right now. I’m relly worried about asking them to fix it becasue I don’t know the right terminology to use without sounding like I’m just complaining.

Update: Thanks for the advice! I pushed back and it turns out that plastic was only 2-mil. I insisted they switch to the 6-mil polyethylene you mentioned and used that 'black death' acoustic sealant on the plates too. I feel way better knowing it’s actualy sealed right now. Glad I didn't just take the contractor's word for it!