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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I don’t know... this is one of those applications that really is designed for an adhesive both from strength and application. We tend to like the notion of mechanical fastening but does it offer any benefit in this type of application and are the materials suited to mechanical fastening?<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'>If you are looking at running a termite shield or vb then mechanical fastening will puncture that?. Is the slab suitable for tapcon – or will it spall or crumble or grab causing screws to spinout or shear. Will the 1” foam and 1” ply combination float over low spots and/ or will the screw hold the floor in suspension over the voids (over time...). will there still be flex between fastening points and will the fastening points be too stiff in comparison to overall flex (too stiff under tile compared to non screwed areas). Even 1” foam is subject to some deformation over time and will this cause screw heads to pop or loosen. Those are some of the thoughts and concerns I would have with mechanically fastening.<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'>A gluedown would arguably be stronger in this type of assembly and has a little more redundancy built into it than a fastener @24oc. Most effective physical termite barriers are adhered now or peel and stick. So an adhered membrane with foam glued over with cemboard glued down strikes me as an ideal use of appropriate material that takes advantage of the benefits of each material and has fewer compromises. The foam/cemboard is essentially providing the same function as the tile membrane so that becomes redundant – so the overall assembly is probably at less cost.<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'>I think if a contractor can they be safely relied upon to properly set tapcons (not easy to do well) gluing down some foam should be a little simpler. <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'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><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>Alan Abrams<br><b>Sent:</b> June-01-11 11:39 AM<br><b>To:</b> Green Building<br><b>Cc:</b> satjiwan@alumni.brandeis.edu<br><b>Subject:</b> Re: [Greenbuilding] fastening a subfloor over foam over a slab<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>so an important question is mechanical versus adhesive fastening. Screw vs Goo, if you will. Without being responsible for the installation personally, I am more comfortable spec'ing mechanical fastening. I'm thinking to fasten the lams of plywood at 8" centers EW, and secure it to the slab with flathead tapcons at 24" OCEW, with 3/4" embedment. <br><br>A remaining question is resistance of the foam to insect infestation. This suggests a rugged vapor barrier over the slab--as for insect supression as for vapor migration. (in this case the basement is well drained, with little risk of significant bulk water anywhere.)<br><br>AA<o:p></o:p></p></div></body></html>