double vapor barrier

I did a presale inspection and the existing 6 mil vapor barrier was torn and did not cover a protion of the crawlspace it had been damaged and was full of holes from construction. I asked for a new 6 mil vapor barrier be isntalled over the old one and to cover all the exposed earth which the seller did

the potential buyers inspector is requiring the original vapor barrier be removed as it will trap water between them,

any thoughts on this ?


There’s a a moisture issue that needs to be addressed. If there’s condensation, find and eliminate the cause instead of getting rid of the second barrier.

Yes, installation of a new ground cover might take a while depending on the crawlspace, but removal of the old one shouldn’t take too long. If I wanted to sell my house I’d rip that thing out of there in no time flat and make a clean job of the new installation.
If I were buying a house and the owners refused to remove the old one, I’d wonder what else they’d skimped on.

I have seen condensation droplets on the underside of a single layer ground cover polyethylene moisture barrier when it is installed without sand/soil/etc. over it. Should we remove this also…it’s obviously doing its job of keeping the soil moisture out of the house! If we put another barrier over a damaged one, what will the problem be? just the same moisture droplets on the underside.

The best way to install these is with a sand drainage layer under them and a sand layer over them to weight them down…but have only seen these in text books. The under layer of sand allows bulk water to easily drain to the soils while the cover layer protects the barrier from damage when travelled over.

A most important item with these barriers is to never allow bulk water to gather on the upper side depressions. This water will not drain and only disappear through evaporation into the space above where you don’t want it! That’s why the barreir was put down in the first place.

I see no problem with the second layer here. Cover it with soil/sand (a good practice) and who will know the difference (as if there is any difference!!)?

It wouldn’t be a double vapor retarder if both are in the same place.

I agree, if they are both in the same place it becomes one, and would be no different than some of the products that are laminated or made up of seven layers to provide a 15 or 20 mil product for vapor retarders.

My only hope is that this second time around it gets lapped at least 12" to 24" or taped properly and no holes or tears in the membrane.

Multiple layers in the same place with the proper protection is always prudent as long as they are protected.

Brian’s suggestion of sand on top is great which I have done many years ago, but need to make sure there is a positive drainage in the crawl space so no laying water would occur that would keep this sand layer wet. If it gets saturated above the vapor barrier, then the vapor barrier whether doubled or not would be found useless to the humidity it would provide to the floor framing.



Makes for a great cat sand-box with the sand on top:D :smiley:

Removing the older vapor barrier is a waste of time in my opinion. Who cares if there is moisture under the barrier. Its job is to keep the moisture where it is…under the barrier. Of course if there is standing water under the barrier… That’s another story.