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RE: Gaps between plywood sheathing

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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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