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RE: Capillary Breaks

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Gail,
 
This has more to do with the flooring planned than heaving.
 
What flooring is planned and how much vapor can it tolerate?  If you have flooring that is relatively insensitive to moisture then you may not need the capillary barrier.  If you have moisture sensitive flooring then you will need all of the above.
 
Arvel
-----Original Message-----
From: GSKWY(--nospam--at)aol.com [mailto:GSKWY(--nospam--at)aol.com]
Sent: Wednesday, February 09, 2005 12:28 PM
To: seaint(--nospam--at)seaint.org
Subject: Capillary Breaks

An article on the web site for a vapor retarder manufacturer said something about putting a capillary break above the vapor retarder  - the capillary break being something like a layer of free draining gravel.
 
This is not the same as the endless ACI 302/360 discussion of a fill layer/base course above or below the vapor retarder,  it is somehow implying (I think) that sufficient moisture might come up through the vapor retarder that you need a capillary break on top of it.
 
I don't see how that can be true - I can see putting a capillary break below the vapor retarder, to prevent heaving right below the vapor retarder,  but it doesn't seem to make sense the other way around.
 
I asked the guy who wrote the article why anyone who do this,  and got this as a reply:
 
"It has been our experience and that of many of the contractors we work with that both ways work."
 
Does anyone have experience with a situation where it makes senses  to put a capillary layer above the vapor barrier? 
 
Gail Kelley