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Re: Can 2x6 T&G roof or floor consider to be a diaphragm?

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Concrete Home Building Council? These numbers look too high. I've been used to the Western Woods User Book values/methodology (Section 10.3) which gives you about 50 plf for joists at 16" oc. With joists a 54" you'd get 50plf x 16/45 = 15plf. Each set of nails develops a force couple and the density of these gives you the shear capacity. These joists are too far apart IMHO.

Jnapd(--nospam--at) wrote:
Are the 2x6's perpendicular to framing or diagonal ? Roof
perpendicular   = 100plf
 diagonal        =  250plf
perpendicular     = 100plf
perpendicular     = 500plf
w/ wood flooring
diagonal = 250plf
w/ wood flooring  =  600plf
I believe it is 2-16d's @ each support min.
2007 CHBC Table 8-8A
Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA
In a message dated 11/18/2009 3:43:03 A.M. Pacific Standard Time, mStuart(--nospam--at) writes:

    It is very likely that the existing deck was horizontally spiked
    together such that the spikes plus the T&G resistance will enable
    the deck to act as a diaphragm.

    *D. Matthew Stuart, P.E., S.E., F.ASCE, SECB*

    *Senior Project Manager*

    *Structural Department*


    *Engineers and Consultants - CMX

    200 Route 9

    Manalapan, NJ 07726

    732-577-9000 (Ext. 308)

    908-309-8657 (Cell)

    732-298-9441 (Fax)



    *From:* ken ng [mailto:zy7up(--nospam--at)]
    *Sent:* Wednesday, November 18, 2009 1:07 AM
    *To:* seaint(--nospam--at)
    *Subject:* Can 2x6 T&G roof or floor consider to be a diaphragm?

    1. 1.  I have a 1945 building and it has 2x6 T&G (2" Vert. and 6"
    Horiz) roof and the floor is nailed directly to beams at 54"o.c.
     Can I consider these are flexural diaphragms with 54” existing
    nail spacing?

    2.  2.  What about additional floor or roof joists that were added
    @ 18” o.c. with new nails at 18” o.c.  Will this be considered to
    be a diaphragm?

    3.   3.  Or ½” plywood shall be added on top of existing 2x6 T&G?

    4. 4.   The drawing plan called out some live load for Storage in
1945. However the hand created drawing was not so clear to read. I could not read the numbers if it's 50#, 75#, 100#, or 125#. Does anyone know what was the 1945 UBC required for this year?

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