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[SEAOC] Re: [SEAOC] Re: [SEAOC] Re: [SEAOC] Number of plywood veneer layers.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)power.net
- Subject: [SEAOC] Re: [SEAOC] Re: [SEAOC] Re: [SEAOC] Number of plywood veneer layers.
- From: smthengr(--nospam--at)sirius.com (Jeff Smith)
- Date: Wed, 10 Jul 1996 08:49:23 -0800
Thank you John and Michael. That was exactly the information I needed to know! Jeff Smith >You've got it almost right. 15/32" and 1/2" plywood sheathing are available >in 3-, 4- and 5-ply layups, and 19/32" and 5/8" plywood sheathing are >typically available in 4- and 5-ply layups. Five-ply plywood is available, >especially in the CA market, but may be a special order item in some cases. >As long as the face grain is across supports, the uniform load capacity is >not affected by the number of plies. When the face grain is parallel to >supports, the cross-panel stiffness and strength are higher when there are >more plies, and thus the panels can support more uniform load. There is a >table in Sec. 23 of the '94 UBC that covers the uniform loads when panels >are applied parallel to supports, as typically occurs for panelized roofs. > >For shear walls and diaphragms, the number of plies does not affect the >shear values (except that the City of LA and County of LA have regulations >which limit the shear values for 3-ply plywood to 200 plf - which APA will >address when cyclic load shear wall tests are completed). The shear values >depend on the panel thickness and grade (e.g., Structural I or regular >Sheathing), fastener schedule, panel layout (for diaphragms and shear >walls), and lumber species. > >When re-roofing over spaced boards, APA has a Technical Note that provides >recommendations on installing roof sheathing panels in this application, >whether parallel to the spaced boards or perpendicular to them (e.g., up the >slope of the roof). > >John D. Rose >APA >Tacoma, WA > > > > > > >>Jeff, >> >>I do not believe that table 23-I-J-1 of the UBC implies any requirement as to >>the number of plys required for the given thickness of plywood. This table >>is only for the allowable shear for a total thickness of plywood. >> >>As I understand it, 3/8" and 1/2" Exposure 1 plywood is only 3 plys. 5/8" >>Exposure 1 plywood is typically 4 plys. If you want a minimum of 4 plys, >>than you need to call for 1/2" structural 1 plywood, or 5/8" Exposure I >>plywood. 5 ply 1/2" structural 1 appears to be more of a special order which >>most contractors do not want to do. Typically in our office we are using >>1/2" structural 1 plywood for all shear walls, since in Los Angeles all 3 ply >>plywood is limited to 200 plf. >> >>Michael Cochran S.E. >>Brian L. Cochran Assoc. >>Los Angeles, CA >> >> >>... >> >> >> > >... ...
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