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Re: Slab on Grade and the Green Code

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I just got back from a job site. I took a look at some 6 mil visquene that was removed during some demo work. It looked like one of grandma's lace curtains. The sand hides the punctures, but can't prevent them in a crummy 6 mil vapor barrier. Also, the workers walk around on the rebar & embed the dobbies & rebar into the sand. If the concrete is pumped it can move the sand into contact with the rebar. The ASTM piece goes into this at length & it's partially discussed in some of the articles in this thread.
Chuck Utzman,PE
ps It's nice to see that there are still some of us still watching the list server

On 12/5/2013 8:56 AM, Lloyd Pack wrote:
Hello Oshin & Board:

Have you been able to get any information on why the GBC wants
no sand over the vapor barrier?  How do the writers of the GBC
expect the concrete to be installed without puncturing the typical
plastic sheet, 0.006" thick, that is used as a vapor barrier?

I'm sure that you know this, but the sand is used over the gravel/base
to protect the underside of the plastic and it's used over the plastic
to protect the plastice from puncture from workers stepping on
the large aggregate in the concrete while placing and screeding the

It would seem that the negatives of puncture, e.g. allowing vapor through
the barrier, outweigh the benefits of not using sand to protect the

I would be curious to know what the creators of the GBC have to say on
this issue.

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