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RE: Wood wall sheathing

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From our helpdesk:



Thomas D. Skaggs, Ph.D., P.E.

Manager, Product Evaluation


7011 S. 19th Street

Tacoma, WA 98466

253-620-7479 (office)

253-620-7235 (fax)





### start helpdesk response ###


The following is in response to your inquiry regarding which side of an APA Rated Sheathing panel should be placed up (or out).  From a structural or durability point of view it does not make any difference which side is placed "up” (or “out”).


The stamped side of APA Rated Sheathing roof panels often goes down so the inspector can more easily access the APA trademark with the panels in place.  Note that many APA OSB sheathing producers make their panels with one rough and one smooth side.  On steep roofs, the rough side of OSB is intended to go up to provide a more secure working surface.  However, the APA trademark itself may occur on either the rough or smooth side.  Plywood sheathing may also be stamped on either side “face” or “back.”


While it is unlikely that a plywood APA Rated Sturd-I-Floor panel would be incorrectly placed because of the differences in the face and back surfaces, very often it is difficult to tell on an OSB APA Rated Sturd-I-Floor panel which side should be placed up.  For this reason, many manufacturers provide a "this side up" or “this side down” stamp to indicate the appropriate face.  This kind of stamp also finds its way onto plywood and OSB panels with asymmetrical tongue and groove edges.  In this case, all of the stamps should be facing up or down so the T&G joints fit flush.  As with APA Rated Sheathing, there is no structural reason for placing either side of an APA Rated Sturd-I-Floor panel up or down.  However, if stamped, plywood APA Rated Sturd-I-Floor panels installed as floor sheathing should be installed as indicated by the stamp since the face ply and cross bands behind the face may be improved veneer grades intended to meet indentation and surface requirements.


The reasons listed above are serviceability related and are traditionally taken to be outside the scope of building codes.  These guidelines also apply to wall sheathing.  It does not matter which side is out.


I hope this information will be of assistance to you.  If we can supply you with any further information please let us know.




Ray Clark
Product Support Specialist
Wood Products Support Help Desk

Southern Forest Products Association
Structural Insulated Panel Association

253-620-7400 (phone)
253-565-7265 (fax)

Neither APA, the Southern Pine Council, the Structural Insulated Panel Association nor their members make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this communication. Consult your local jurisdiction or design professional to assure compliance with code, construction, and performance requirements. Because APA and the Southern Pine Council have no control over quality of workmanship or the conditions under which wood products are used, they cannot accept responsibility of product performance or designs as actually constructed.






From: Michael Gregory [mailto:tsemike(--nospam--at)]
Sent: Friday, November 07, 2008 08:51
To: seaint(--nospam--at)
Subject: Wood wall sheathing


Is there any reason that wood sheathing needs to be installed on walls with the smooth surface out?  The layout lines are on the rough side.  One contractor is telling me that he was red-tagged by a BO for installing the rough-side out on a recent project in another jurisdiction.    




M Gregory