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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The foam at 5” thickness acts as a v.b. as does the ply (a
factor of thickness with eps). The granular base (gravel or sand) is the
capillary break from groundwater but also is what forms the level base so it
either needs to be fine enough to compact and screed (level) and/or the foam
needs to be of sufficient thickness to span any discrepancies in the base
(laziness in levelling). I’ve found that coarse sand (cement sand)
compacts well and screeds well to form a decent level. 4” foam will span
irregularities on roughly 16” centers and even more once bonded to ply. 6”
of foam is great in what it will span. (levelling the sand can be improved with
a water/latex spray mix).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The basic technique is that sand is compacted to within an inch
or so of level and then you place screeds in the sand at final level and fill
in and screed so the sand is level. Lay the foam down and spray adhesive in an
overlapped 4” squiggle pattern on the foam, lay down the t&g ply overlapping
foam seams and weight it down, stagger the ply seams, etc. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Depending on the area the sand can be screeded in sections
followed by foam and ply – glue can set in a relatively short time
depending on temp/humidity so the weight can be shifted to the next area (polyurethane
foam adhesion is helped in moistening the ply backs)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>1-1/8” ply is major overkill as the foam is providing the
span and the ply is only acting as a skin and a nailbase. The extra thickness
could work against you. The concern with ply is that it is flat. If it is
overly thick and is warped it will take a lot of weight to flatten to the foam
and any warpage can delaminate and form pockets. I’ve found 5/8 t&g
to be the best working minimum that works but my personal preference is 2
layers of ½” ply laminated for ease of installation and stiffness as it
tends to flatten and compensate for any poor bond areas and you can eliminate
having to set the t&g by using the overlap. It is hard to describe in words
but this assembly requires good workpersonship in the layup so it is best to
work with an assembly that can compensate for any problems. I’ve found
the best assembly is thick foam that can span (and insulate) and thin layers above
layered to form a stiff skin that spans any pockets and provides sufficient nailbase
for wood flooring and sufficient stiffness for tile. Think of it like a fibreglass
layup.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The end product even with a single 5/8” layer tends to be
flatter and stiffer than a floor on joists and if a solid wood floor is being
nailed to that the final assembly is quite stiff and is basically a floating
structural floor. Anticipated deflection can be as much as a ¼ “
depending on loading but I’ve gone back to look at floors that had a
combination of wood and tile and have not seen any movement that has popped a
grout line.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>
greenbuilding-bounces@lists.bioenergylists.org
[mailto:greenbuilding-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Reuben
Deumling<br>
<b>Sent:</b> April 20, 2011 10:38 PM<br>
<b>To:</b> Green Building<br>
<b>Subject:</b> Re: [Greenbuilding] building floor on top of rigid foam...
(basement/garage retrofit)<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>Any particular reason not to
vary the relative thicknesses of the two materials? I've planned to do as you
say, but have secured at a good price enough 2.5" foam and 1-1/8"
T&G plywood. I was going to put these atop compacted 1/4" minus
gravel, with a vapor barrier (or not? I see you didn't mention one). <br>
<br>
Thanks for any thoughts.<br>
<br>
Reuben Deumling<o:p></o:p></p>
<div>
<p class=MsoNormal>On Wed, Apr 20, 2011 at 9:18 PM, JOHN SALMEN <<a
href="mailto:terrain@shaw.ca">terrain@shaw.ca</a>> wrote:<o:p></o:p></p>
<div>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;color:#1F497D'>The basic spec. is rigid eps board (minimum
4”) on a level surface w/ t&g ply sheathing laminated directly
to the foam with a suitable adhesive. That is it. The level surface does
not have to be concrete – it can be a granular base (sand). </span><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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<p class=avgcert>No virus found in this message.<br>
Checked by AVG - <a href="http://www.avg.com">www.avg.com</a><br>
Version: 10.0.1209 / Virus Database: 1500/3586 - Release Date: 04/20/11<o:p></o:p></p>
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