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Editor's Notepad

What's the Best Vapor Barrier for a Concrete Slab?

Scott Gibson, contributing writer

7 users recommend

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Arlene DiMarino is aware that a plume of toxic underground water from an EPA Superfund site is not far from her home, and her concern is that volatile organic compounds will permeate the foundation and concrete slab in her basement. She's planning to pour a new layer of concrete over the old and wonders what type of vapor barrier she should use.

That's the subject of this week's Q&A Spotlight.

The usual solution would be 6-mil polyethylene with taped seams, but a number of posters think there are much better products on the market. Suggestions include Tu-Tuf, Slab Shield, and Stego Wrap, among others. Some suggest an active radon mitigation system be installed.

But, are bullet proof vapor barriers really that important? One poster points to comments by Joseph Lstiburek, a well known building scientist, who suggests that a few holes in a sub-slab vapor barrier make practically no difference in its effectiveness as a moisture barrier.

The question is whether that point of view applies here.

Read the entire article at Fine Homebuilding's Green Building Advisor.

Further Resources

What's the difference: Vapor barriers and vapor retarders?

Retrofitting a vapor barrier

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Comments (5)

jsmyrick writes: Does anyone one make a vapor barrier stong enough to keep out toxic spam?
Posted: 1:24 pm on December 27th

BeattieBuilt writes: Best practice here in BC has us placing poly as per discussed to perimeter with penetrations caulked, in addition to a perimeter of Big-O or slotted rigid 4"pipe looped in pea gravel trench 12" deep under slab, to a tee up through the slab and tied to 4" ABS pipe up and through roof with possible inline low cfm draw fan, this creates a slight vacuum under slab and radon takes the easy way out. Hope this is useful.
Posted: 10:07 am on November 29th

Brados writes: Since we were running hydronics, we laid down 4" of closed cell 3lb foam before pouring the slab. I know this works from an insulation/ water vapor barrier standpoint....but will it also work to keep out the nastiness discussed in this article?
Posted: 1:17 pm on November 8th

pizza writes: Hey, what's with the spam posts about buying t-shirts and shoes?

This is a Homebuilding website not a place to promote someone's website for buying knock off junk.

Someone notify the webmaster here.
Posted: 8:56 am on November 8th

fren writes: 15mil stego wrap(yellow) is the way to go. Buy the appropriate tape from the supplier, standard house wrap tape will not do.
Make sure you have help, smallest role weighs 150 pounds+.
Posted: 5:52 pm on November 5th

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