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The alkalinity of the concrete will destroy the vapor barrier when it is in
direct contact plus it will cause curling.  Use a real vapor barrier or at
least a 10 mil polyurethane sheet.   Use the cushion, but I would use
crusher fines.  Crusher fines compact better and hold when you drag a pump
hose across them.  

Place the slab as early as possible to allow enough time for the water vapor
in the slab and the crusher fines to pass through and dry.  Use a moisture
meter to determine when you can adhere the flooring.

Harold Sprague

> -----Original Message-----
> From:	NDZ28(--nospam--at) [SMTP:NDZ28(--nospam--at)]
> Sent:	Tuesday, April 25, 2000 11:36 AM
> To:	seaint(--nospam--at)
> Subject:	SLAB ON GRADE
> Just hoping I can get a basic question clarified. I  have a client  I'm
> doing 
> a series of homes for, and he wants me to specify that the slab on grade
> be 
> placed directly over the vapor barrier, (no sand between) He claims that
> when 
> sand over the vapor barrier is moistened prior to pouring concrete, sand
> will 
>  never dry out,  the moisture from the sand will travel through the slab
> for 
> a very long time causing bubbleing in the vinyl flooring, prevents  wood 
> flooring from sticking to concrete, etc. I've always believed that the
> sand 
> aids the curing of the slab.  The caveat is that vapor barrier is
> installed 
> properly and not punctured during placement of concrete. Any help is 
> appreciated.
> Andy Vidikan