Results 1 to 7 of 7
  1. #1
    Jim B. Robinson's Avatar
    Jim B. Robinson Guest

    Question # Plys in Plywood

    I'm currently studying HI - didn't know what other forum to post to.

    This is in reference to plywood facts, not the inspection process. Our exterior inspection manual states "There are always an odd number of layers." And the next paragraph states: "Panels are always strongest in their long axis, though, since there are always more plies with their grain oriented with the long axis."

    This didn't sound correct, so I took a jaunt down to my basement to look at some cut-offs. The 1/2" CanPly DouglasFirPlywood is 4 plys thick, each layer approx. 1/8". The two center core plys are oriented in the same direction and together oriented 90deg. between the face and back.

    Another issue states: "(The tongue-and-groove approach is only common with plywood)" This is incorrect as 5/8" OSB t&g is readily available, in my locale anyway.

    I've searched the net for other sources, with little luck, so here I am asking for plywood facts. I realize this doesn't involve inspection per se, I just like to know I'm reading/learning qualified material.

    Comments?

    Thanks,
    Jim

    Similar Threads:
    Inspection Referral SOC

  2. #2
    Join Date
    Mar 2007
    Location
    Plano, Texas
    Posts
    4,170

    Default Re: # Plys in Plywood

    This just goes to show you, never trust facts from only one source. If you can't document from reliable sources, question the "fact" and always question books from home inspection schools.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  3. #3
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,251

    Default Re: # plies in Plywood

    I have also seen that 4-ply plywood at the Big Box stores.

    As I recall, though, structurally rated panels will have an odd number of plies, typically 3, 5 or 7 plies, with the two face plies and the odd plies all oriented with the face grain in the long axis, with the even plies perpendicular to the long axis.

    That information was correct in that the plywood is stronger in the direction of the face grain, even with 4 plies as the inner plies have more defects in the plies than the outer plies.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  4. #4
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
    Posts
    4,549

    Default Re: # Plys in Plywood

    If this looks wrong, you now know why.

    ***IMPORTANT*** You Need To Register To View Images ***IMPORTANT*** You Need To Register To View Images

  5. #5
    Jim B. Robinson's Avatar
    Jim B. Robinson Guest

    Default Re: # Plys in Plywood

    I emailed Certiwood and received this reply.

    Jim,

    Your are correct. This is likely an old publication. An even number of plies is allowed. And for typical Canadian softwood sheathing and select grade plywood the veneer thickness is 1/8. Good one side, concrete formwork and other appearance/specialty plywoods may use different veneer thickness.

    Feel free to call with any further questions.

    Best Regards,

    Paul Jaehrlich, P. Eng.
    Manager, Technical Services
    735 West 15th Street, North Vancouver, BC, V7M 1T2
    Direct: 604 981-4182
    Fax: 604 985-0342
    www.certiwood.com



    Testing, Certification, Inspection and Product Development for the Wood Industry


  6. #6
    Jim B. Robinson's Avatar
    Jim B. Robinson Guest

    Default Re: # plies in Plywood

    Quote Originally Posted by Jerry Peck View Post
    That information was correct in that the plywood is stronger in the direction of the face grain, even with 4 plies as the inner plies have more defects in the plies than the outer plies.
    Agreed.


  7. #7
    Join Date
    Mar 2007
    Location
    Knoxville, TN
    Posts
    2,446

    Default Re: # Plys in Plywood

    Look at Baltic Birch plywood if you want to see a lot of layers/plys.


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •