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RE: Slab on Grade and the Green Code

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Paul listed some good references.  The first thing is to only put vapor 
barriers where you need them.  I do not like the US Green Building Council 
getting into this area.  They often get into areas that is beyond their 
expertise.  I had a project in the interior of Alaska where the designer 
wanted an easy "point" so a bike rack and shower was installed.  They got 
the point and tore out the bike rack.  I don't want to get into a rant 
about the USGBC, but their time will pass and true energy conservation will 
 come.

If the Properly done, vapor barriers are expensive. Some other 
considerations: Always, ALWAYS have a preplacement meeting with ALL of the 
contractors (testing lab, pumper, concrete supplier, vapor barrier mfgr., 
roofing contractor, concrete supplier, etc. ) for a slab on grade.  Have an 
 agenda regarding responsibilities and timing of activities.  Select a 
"vapor barrier" and not just a 10 mil poly.Vapor barrier penetrations 
should be flashed Laps need to be sealedVapor barrier installation is best 
done by a roofing contractor.  They understand how to maintain the 
integrity of the barrier.  The bottom of the concrete slab should be 
horizontal with no constraints (like thickened areas).  Provide a foam 
layer around columns to avoid the column constraining the slab on grade. 
Do not tie the slab on grade to any perimeter elements.  Allow the slab to 
float.  I prefer placing a capillary break (3/8" open graded rock) below 
the vapor barrier and a layer of crusher fines above the barrier.  Use 
dobies to elevate the reinforcing steel.  The crusher fines compact nicely 
and protect the barrier during placement of reinforcing steel and placement 
 of the concrete even while dragging a horizontal line pump over it. 
Provide venting in the open graded rock to allow any water vapor to escape 
(similar to radon venting).  To minimize shrinkage and curling and water in 
 the slab:  Use a polycarboxylate high range water reducer to minimize the 
water in the SOG.  Use 8 to 18 percent on the aggregate gradation to 
minimize the amount of cement paste and water.  And use good curing 
techniques.  If pressed on time, use a dehumidifier in the space to dry out 
 the SOG for seamless flooring installation and have the SOG moisture 
monitored at times and keep monitoring it for a period after the 
dehumidifier is off.

Regards,
Harold Sprague

> From: PRansom(--nospam--at)PaulRansom.ca
> Date: Tue, 10 Dec 2013 09:19:57 -0500
> Subject: Re: [SEAINT-SEAOSC] Slab on Grade and the Green Code
> To: seaint-seaosc(--nospam--at)mail-list.com
> 
> The researcher's friend  . Google
> 
> <http://cirrus.mail-list.com/seaint-seaosc/29696200.html>
> 
> from 1960 (residential 4 mil)
> 
> <http://archive.nrc-cnrc.gc.ca/obj/irc/doc/pubs/bpn/8_e.pdf> from 1978 
> and referencing prior California tests
> 
> <http://www.nrc-cnrc.gc.ca/ctu-sc/files/doc/ctu-sc/ctu-n44_eng.pdf>
> residential
> 
> <http://cirrus.mail-list.com/seaint-seaosc/64391732.html>
> 8-eng.pdf
> 

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