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Re: Vapor Barriers

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If you are going to allow holes to be punched in the vapor barrier ( which I am
not advocating ) the trick is to use the proper gradation of subbase. Only
course sand or preferably gravel should be specified. Fine to medium sand may
allow water to "wick up".

Horning, Dick/CVO wrote:

> My (not so friendly) Geotech prof told us that capillary action can act over
> 1 foot vertically in sand, as I remember it.  So if you put down 4 to 6
> inches of sand above or below the vapor barrier, and your slab is on a
> fine-grained soil with the ground water table close enough to the surface,
> the ground water can migrate through the holes in the vapor barrier and
> right up to the bottom of the slab.
>         -----Original Message-----
>         From:   Jim Kestner [SMTP:jkestner(--nospam--at)]
>         Sent:   Wednesday, October 14, 1998 1:17 PM
>         To:     seaint(--nospam--at)
>         Subject:        Vapor Barriers
>         Although some of you referred to the vapor barrier as a capillary
> break,
>         I believe it is the course self draining granular subbase below the
>         vapor barrier that is intended to be the capillary break (ask your
>         friendly Geotechnical Engineer) and the vapor barrier is just
> intended
>         just stop upward vapor transmission. That is why I think it may be
> OK to
>         punch holes in the vapor barrier (although I have only done this
> once or
>         twice many, many years California) for the reasons that
>         William Riddle stated.