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RE: Vapor barrier with void form?

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I agree that painting the top of void form would be a waste of time.
However, one option we considered for a vapor barrier would be to place
the vapor barrier membrane over the top of the void forms - this would
permit the void form to deteriorate from the moisture below. 

The membrane could be taped at the joints, but there still would be some
question as to how effective it would be after the void forms collapse.
This also would require the vapor barrier to be in contact with the
bottom of the concrete slab, as placing granular material above the
vapor barrier and void form does not seem practical. Thus, this is not a
great solution. 

Another alternative we are considering is a sealer applied on top of the
concrete (below the tile floor finish), in lieu of a vapor barrier below
the concrete slab. We will discuss this option further with the tile

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)


	From: GSKWY(--nospam--at) [mailto:GSKWY(--nospam--at)] 
	Sent: Monday, April 04, 2005 11:41 AM
	To: seaint(--nospam--at)
	Subject: Re: Vapor barrier with void form?
	A related point that does not at all answer the question.
	At World of Concrete a year ago,  I spent a while talking to
someone from a major void form manufacturer which I will not identify,
since some people seem to think it is inappropriate to  give any
pertinent information about what you are discussing, if such information
is negative.
	At any rate, they were heavily advertising the fact that they
were now making a void form with an integral vapor retarder (i.e. they
painted the top surface with something that impeded vapor transmission.)
	I asked what the point was, since when the form deteriorated the
vapor retarding properties were lost. 
	 The individual to whom I was speaking admitted it was
ridiculous but said people (engineers?  slab on ground "experts"?) were
asking for it, so they were making it.
	Gail Kelley

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