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RE: Vapor Barriers

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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)somervilleinc.com]
	Sent:	Wednesday, October 14, 1998 1:17 PM
	To:	seaint(--nospam--at)seaint.org
	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 ago....in California) for the reasons that
	William Riddle stated.