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Re: Roof Construction Advice

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Joe & Scott
Thanks for the advice.
Why is it unlikely that the plywood would not be an
effective diaphragm?  
Irv


--- Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu> wrote:

> Irv:
> 
> I agree with Joe...it is highly unlikely that the
> plywood would be able to
> effectively act as your diaphragm.  What you are
> describing is rather
> similar to a Structural Insulated Panel (SIP) even
> though it is not a SIP.
> When SIPs are used as a roof system including as a
> roof diaphragm, it is
> the interior SIP skin that "does the work".  In this
> manner, the T&G in
> your case will be like the interior skin of a SIP.
> 
> As to nailing of the plywood to the 2x4s, I don't
> see the deformation of
> the EPS foam being a huge issue, especially if they
> are using a nail gun.
> If they are doing it hand, I still don't see it
> being a problem, but
> certainly reserve the right to be wrong.
> 
> If I may suggest (which also is slightly a "plug"),
> why not just use SIPs
> instead of the EPS foam plus 2x4s plus plywood?  You
> could do a true
> structural SIP if you wanted (i.e. a skin of OSB
> adhered to each side of
> EPS foam) or a "non-structural" SIP of just one skin
> of OSB on the top
> side of the EPS foam.  It would minimze the amount
> of nailing that you
> might have to do and eliminate some lumber (you
> would still have splines
> at the panels joints, but likely not nearly as many
> 2xs as what you are
> likely to have with what you describe).  Plus, if
> you do a "true"
> structural SIP, then you will have an interior skin
> of OSB right on top of
> the T&G that you could use as the diaphragm...if you
> don't want/can have
> the diaphragm to be the T&G.
> 
> Joe:
> 
> As to screws, I don't know what he specifically
> plans to use, but he
> certainly can use "SIP" screws.  These are roughly
> 1/4" diameter screws
> that come in lengths of upto about 15".  This is
> what we typically use to
> attach SIP panels together.  The other option is to
> use "SIP" spikes
> (really long nails).
> 
> Regards,
> 
> Scott
> Adrian, MI
> 
> 
> On Fri, 3 Feb 2006 Jnapd(--nospam--at)aol.com wrote:
> 
> > Irv:
> >
> > The 2x T&G is your diaphragm the upper plywood is
> to cover insulation  and
> > attach the roofing material. The 2x4 below plywood
> is backing for  nailing.
> > What is the screw type and embedment required in 
> purlins?
> >  What is the wind uplift loads on roof ?  The
> screws should  resist this
> > uplift load so you don't loose the plywood in a
> storm.  Purlins  need to resist
> > uplift load also.
> >
> > Joe  Venuti
> > Johnson & Nielsen Associates
> > Palm Springs,  CA
> >
> >
> 
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