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RE: Visqueen under slab in Arizona

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I don't know about other states.  But in California only water based
glues are allowed for carpet and vinyl tiles.  Moisture will cause
flooring problems.  

Vince Yu
Pickard Architects

	----------
	From:  Sprague, Harold O. [SMTP:SpragueHO(--nospam--at)bv.com]
	Sent:  Monday, January 17, 2000 11:01 AM
	To:  
	Subject:  RE: Visqueen under slab in Arizona

	George,

	The reason for the Visqueen is to serve as a vapor barrier.  

	If concrete is placed directly on top of Visqueen, 3 things
happen:
		1.	The slab will have excessive curl
		2.	Unless you use 10 mils or greater, the Visqueen
will have
	many punctures
		3.	Concrete placed directly on top of Visqueen will
result in
	the degradation of the Visqueen due to the
alkalinity
	of the concrete

	The purpose of retarding the vapor is to assure that any adhered
finishes
	will not be damaged by the water vapor migrating up through the
slab.

	If water vapor is not desirable, I would:
		1.	Use a capillary break of open graded crushed
rock as a base.
		2.	Provide a vapor barrier like the Mirafi or some
other real
	barrier
		3.	Provide a layer of compacted crusher fines over
the vapor
	barrier
		4.	Place the concrete on the crusher fines.

	I have seen good performance on slabs on grade with no vapor
barrier with
	glued carpet and vinyl tile, but these slabs were on coarse
sand.  And I
	have seen delamination of seamless flooring on slabs on grade
with vapor
	barriers.  It is a function of the finish sensitivity, and the
tendency for
	water vapor to form.  I like a capillary break, no matter what
(don't put a
	SOG on clays or silty sands).

	Regards,
	Harold Sprague

	> -----Original Message-----
	> From:	George Richards, P.E. [SMTP:george(--nospam--at)BORM.com]
	> Sent:	Monday, January 17, 2000 12:39 PM
	> To:	'seaint(--nospam--at)seaint.org'
	> Subject:	Visqueen under slab in Arizona
	> 
	>  We are being told that it construction practice in Arizona
along the
	> Colorado river is to not place Visqueen under residential
floor slabs.
	> Would anyone please comment.
	> 
	> George Richards, P. E.
	>