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

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Can 2x6 T&G roof or floor consider to be a diaphragm?
• From: Chuck Utzman <chuckutzman(--nospam--at)gmail.com>
• Date: Thu, 19 Nov 2009 08:03:14 -0800

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)aol.com wrote:
```
```Ken
```
Are the 2x6's perpendicular to framing or diagonal ? Roof
```perpendicular   = 100plf
diagonal        =  250plf
```
Floor
```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)cmxengineering.com 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*

*Associate*

*Engineers and Consultants - CMX
<http://www.cmxengineering.com/index.htm>*

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 308)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart(--nospam--at)CMXEngineering.com

```
```    ------------------------------------------------------------------------

*From:* ken ng [mailto:zy7up(--nospam--at)yahoo.com]
*Sent:* Wednesday, November 18, 2009 1:07 AM
*To:* seaint(--nospam--at)seaint.org
*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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