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RE: Gaps between plywood sheathing

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Plywood will really buckle if gaps are not provided in shear walls under
buildings.  An example of this was on about 23 townhomes in Pacifica where
the contractor tightly fit the plywood panels in the underportion of
down-hill buildings.  Pacifica faces the ocean with lots of fog and crappy
weather.  Making the contractor provide the proper ventilation, as shown on
the drawings, became confrontational.  This is the same fellow I mentioned
in an earlier post that was removed from the site by the sheriff.

Neil Moore,  S.E.
neil moore and associates


At 04:58 PM 4/18/2001 -0800, Haan, Scott M. wrote:
>Gaps are required in plywood that is exposed to the weather to act as
>isolation joints.  This is because the plywood will expand when moisture is
>applied.  If you don't do it then the plywood will buckle.  
>
>The gaps would not be required for a dry condition. Floor sheathing for
>interior applications for example is required to have tounge and groove
>edges or be blocked.  T&G edges are self defeating if you leave a space
>between the plywood.
>
>Scott M Haan P.E.
>Plan Review Engineer
>Building Safety Division http://www.muni.org/building
>Development Services Department
>Municipality of Anchorage
>phone:907-343-8183  fax:907-249-7399
>mailto:haansm(--nospam--at)ci.anchorage.ak.us
>
>
>
>-----Original Message-----
>From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
>Sent: Wednesday, April 18, 2001 3:59 PM
>To: seaint(--nospam--at)seaint.org
>Subject: RE: Gaps between plywood sheathing
>
>
>Section 6 (Revised November 1, 1948) of the DFPA (Douglas Fir Plywood 
>Association) Technical Data Handbook describes how the lateral bearing 
>strength of nailed plywood joints was developed.  It has curves so that 
>knowing the edge distances of the nails in the plywood and in the stud, the 
>ultimate capacity of the nail can be determined.  Tests were performed on 
>5/16", 3/8", 1/2", 5/8" and 3/4" plywood with 6d, 8d, 10d, and 16d common 
>nails.  It is only 7 pages long, and if APA would not object, I can provide
>a 
>copy to Dennis Wish for inclusion on his Structuralist web site.
>
>A. Roger Turk, P.E.(Structural)
>Tucson, Arizona
>
>George Richards and Michael Bryson wrote:
>
>. > The numbers do not add up and I have never seen anything in APA lit. to
>. > address this issue.  Engineering Judgement. 
> 
>. > George Richards, P. E.
>
>. > -----Original Message-----
>. > From: Michael Bryson [mailto:michael.bryson(--nospam--at)englekirk.com]
>. > Sent: Wednesday, April 18, 2001 1:27 PM
>. > To: seaint(--nospam--at)seaint.org
>. > Subject: Gaps between plywood sheathing
>
>
>. > Typically you install sheathing with a 1/8" gap between sheets to allow 
>. > for some expansion, correct? If the sheets are supported by a 2x framing
>. > member, how do you get your edge distance for a 10d nail?
>
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