This is one of the succinct summaries of this sandwich:<br><br><div class="gmail_quote">---------- Forwarded message ----------<br>From: <b class="gmail_sendername">JOHN SALMEN</b> <span dir="ltr"><<a href="mailto:terrain@shaw.ca">terrain@shaw.ca</a>></span><br>
Date: Wed, Apr 20, 2011 at 9:18 PM<br>Subject: Re: [Greenbuilding] building floor on top of rigid foam... (basement/garage retrofit)<br>To: <a href="mailto:ArchiLogic@chaffyahoo.ca">ArchiLogic@chaffyahoo.ca</a>, Green Building <<a href="mailto:greenbuilding@lists.bioenergylists.org">greenbuilding@lists.bioenergylists.org</a>>, <a href="mailto:satjiwan@alumni.brandeis.edu">satjiwan@alumni.brandeis.edu</a><br>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I missed this thread somehow. I can testify that putting a floor
directly on eps foam is a great system. I have done this in a number of
renovations, new homes and a school. 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></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The real point of this approach is to avoid the use of concrete
or in the case of insulating on existing concrete to isolate from moisture and
to minimize the use of unnecessary materials. </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">As for materials the ‘suitable adhesive’ is
generally specified as a polyurethane foam adhesive (enerbond or equiv.). If
the finished floor is to be ¾” solid wood nailed - I specify a min.
5/8” t&g ply sheathing. If it is tile I generally specify either a
thickset mortar directly on the foam (w/reinf.) or an additional layer of
½” ply laminated and fastened @ 3” o.c. I’ve found that most
contractors get the concept pretty quickly but the trick is that in putting
down the ply it needs to be flattened and weighted down while the adhesive sets
(concrete block, buckets with sand, etc...)</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">For your application I would eliminate any subfloor wood framing
(sleepers). Waste of time and material. eps boards can be ordered cut to the
thickness needed for the finished product. Using foam on an existing slab it is
nice to have additional thickness – 5-6” foam can span any
deflections or defects in the concrete. I would spot adhere the foam to the
concrete. </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Essentially the finished floor (eps and ply) is a weight bearing
floating floor that can carry standard interior partition loads well. It is a
pretty nice floor.</span></p>
</div></div></div><br><br><div class="gmail_quote">On Tue, Apr 3, 2012 at 10:32 AM, Benjamin Pratt <span dir="ltr"><<a href="mailto:benjamin.g.pratt@gmail.com">benjamin.g.pratt@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
wouldn't 1/2 plywood warp over time? I don't knwo the procedure.<br>
<div class="HOEnZb"><div class="h5"><br>
On Tue, Apr 3, 2012 at 12:28 PM, Michael O'Brien <<a href="mailto:obrien@hevanet.com">obrien@hevanet.com</a>> wrote:<br>
> Hi, Reuben--<br>
><br>
> To clarify what is being finished--I'm sure it's obvious, but the plywood<br>
> should be exterior grade. Practically speaking, moisture won't be able to<br>
> pass through the phenolic adhesive between the plys. Are the two layers<br>
> free-floating over the sand? Is that OK--they won't move when there's<br>
> traffic on them?<br>
><br>
> It seems like a hardwood would work better than a softwood like fir,<br>
> costlier but might hold up to traffic better, especially on half-inch<br>
> sheets. (I wonder if 5/8" might be worth it for extra stiffness?)<br>
><br>
> I'd suggest coating both sides and all edges with a water-resistant finish,<br>
> while the plywood is dry. Have you looked at Miller's Evolution satin<br>
> exterior paint? It's reasonably priced for its performance. Miller staff can<br>
> help decide if a wood filler is needed. The satin finish would make it<br>
> easier to clean.<br>
><br>
> Might be good to leave a little space between edges for expansion and to<br>
> stagger the joints between the two layers, to slow any moisture from the<br>
> sand layer.<br>
><br>
> Is that about what you already figured out? :^ )<br>
><br>
> Best,<br>
><br>
> Mike O'Brien<br>
><br>
><br>
><br>
> On Apr 3, 2012, at 9:32 AM, Reuben Deumling wrote:<br>
><br>
> I'm planning on assembling a floating double layer of 1/2" plywood over foam<br>
> over sand that JOHN SALMEN described here in the past, and as this is for a<br>
> basement wood shop I'm wondering if anyone has suggestions about what to<br>
> seal or paint the plywood with to maximize its longevity?<br>
><br>
> Thanks.<br>
><br>
> Reuben<br>
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<br>
<br>
</div></div><span class="HOEnZb"><font color="#888888">--<br>
<br>
<br>
b e n j a m i n p r a t t<br>
<br>
professor art+design<br>
the university of wisconsin stout<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
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