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RE: Safety factors for attaching screws to OSB

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I did a bit of digging on this.  In general ASTM Standards related to OSB and structural composite lumber would require load factors of 5.0 on the average test value (see below reference list) for smooth shank nails (standards require tests on 8d common nails).  This yields an ASD Design value at 10 years duration, appropriate load duration factors are applied to this ASD Design value, based on duration of load.

APA publication E830 (2005) was apparently revised to state load factors of "5 or 6".  Finally APA publication TT-051 specifically mentions using a factor of safety of 5.0.  Both of these publications are available at our website, go to the publication area and search for "E830" and "TT-051", respectively.


REFERENCES
ASTM D5456 Standard Specification for Evaluation of Structural Composite Lumber Products

ASTM D7033 Standard Practice for Establishing Design Capacities for Oriented Strand Board (OSB) Wood-Based Structural Wood Panels

Fastener Loads for Plywood - Screws, Technical Note E830D -- August 2005

Screw Withdrawal from APA-Trademarked OSB, Technical Topic TT-051A -- February 2007


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Thomas D. Skaggs, Ph.D., P.E.
Manager, Product Evaluation
Technical Services Division
APA - The Engineered Wood Association
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ph: 253/565-6600
fx: 253/620-7235
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-----Original Message-----
From: Jared Keyser [mailto:jkeyser(--nospam--at)lcmf.com]
Sent: Sunday, March 02, 2008 13:13
To: seaint(--nospam--at)seaint.org
Subject: Safety factors for attaching screws to OSB

Drew,

I use FS of 6 times the load duration factor which comes out close to 4.  This is based on the APA technical note for "Fastener Loads for Plywood - Screws  Number E830C, December 1995".  Tested values for OSB should have a similar factor of safety.

Jared



From: Drew Morris <dmorris(--nospam--at)bbfm.com>
To: SEAINT <seaint(--nospam--at)seaint.org>
Subject: Safety factors for attaching screws to OSB

I have it in my mind that the recommended safety factor for screws in
withdrawal from OSB is a minimum of 4.  Does anyone know what APA
publication lists this?  I have been searching the publications that I
have and cannot find it.  I have a call into APA.

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