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Re: Roof Construction Advice

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It largely depends on how far of a span you are talking about...just like
it would be for a purlin or beam or any other roof structural member.

Also, are you talking net uplift pressure (i.e. after accounting for dead
load that conteracts the wind) or gross uplift?

You can easily look at SIP load span tables from any of the major
manufacturer (all have some sort of an evaluation report with load span
tables).  If I use our load span tables, assuming a 12 ft panel span and
OSB surface splines:

- a 4" nominal panel could take 13 psf of net uplift
- a 6" nominal panel could take 25 psf of net uplift
- an 8" nominal panel could take 35 psf of net uplift
- a 10" nominal panel could take 47 psf of net uplift
- a 12" nominal panel could take 57 psf of net uplift

And the values would go up from there if we started talking about 2x
splines or LVL splines at either 4' oc or 2' oc or going to double 2x or
LVL splines.

Now, those above values "assume" that there is adequete connection from
the SIP panels to the supporting structure.  This is something that would
have to be done on a case by case basically is a matter of
adjusting the #/spacing of the panel screws that are used to attach the
roof panels to the walls/purlins/joists/etc.  In otherwords, you take the
"reaction" from your panel due to net uplift and determine the number of
necessary screws based upon the capacity of the screws (rougly 110 lbs per
screw with no sheet metal washer; roughly 150 lbs per screw with a 2"
diameter sheet metal washer...the failure mode of the panel screw is head
pulling through the OSB).


Adrian, MI

On Fri, 3 Feb 2006 Jnapd(--nospam--at) wrote:

> Scott:
> How easy is it to handle 12 or 15 psf uplift with the SIP's.
> Joe  Venuti
> Johnson & Nielsen Associates
> Palm Springs,  CA

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