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Re: Proposed roof design

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Bill,

As it sits, I don't see a viable diaphragm.  As I see it, the 16D at 12 from
the 1x through the insulation and 19/32 foil sheathing is worthless.  Apart
from the inevitable shiners that will appear everywhere, there is inadequate
penetration for both the 16d and the sheathing nails to the 1x strapping.

With rearrangement of the sleepers and cutting the insulation into 2' strips
instead of 4' sheets, you could develop an unblocked diaphragm within the
sheathing and sleepers separate from the roof rafters, then solid block all
boundary edges for shear transfer.  Limit the diaphragm to low values and
short nails.
Run the ply the other way and lose the 1x4's entirely.

Paul Feather PE, SE
pfeather(--nospam--at)SE-Solutions.net
www.SE-Solutions.net
----- Original Message ----- 
From: "Bill Allen" <T.W.Allen(--nospam--at)cox.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, October 01, 2003 1:06 PM
Subject: Proposed roof design


> Ladies and Gentlemen;
>
> An architectural client of mine is proposing an unorthodox (to me) roof
> design and has asked me to review. I have some concerns, but I thought I
> would solicit comments from the engineering community before I
> responded.
>
> When he first described the system to me, I thought the sheathing would
> be applied directly on the roof rafters.
>
> See: http://members.cox.net/ballense/roof.htm
>
> Criteria:
>
> UBC/CBC 70 MPH Wind, Exposure C
> Seismic Zone 4 (although residential construction and diaphragm shears
> should be small < 150 PLF).
>
> Your comments would be most appreciated.
>
> Thanks,
>
> T. William (Bill) Allen, S.E. (CA #2607)
> V/F (949) 248-8588
> San Juan Capistrano, CA
> http://members.cox.net/ballense/
>
>
>
>
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