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  1. #1
    Join Date
    Dec 2009
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    St. Louis
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    Default Which is stronger

    Just a general question:

    If you have a piece of plywood, glued and screwed/nailed/bolted to the same dimensions as a piece of lumber ie: 2x5....2x8 , does the plywood have more or less tear apart strength then the lumber ?

    (If you pulled on both ends of the built up plywood and the lumber, with the same force, which would come apart first ?)

    Thanks
    Frank Albanello

    Inspection Referral SOC

  2. #2
    Join Date
    Mar 2007
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    Spring Hill (Nashville), TN
    Posts
    5,847

    Default Re: Which is stronger

    Quote Originally Posted by Frank Albanello View Post
    Just a general question:

    If you have a piece of plywood, glued and screwed/nailed/bolted to the same dimensions as a piece of lumber ie: 2x5....2x8 , does the plywood have more or less tear apart strength then the lumber ?

    (If you pulled on both ends of the built up plywood and the lumber, with the same force, which would come apart first ?)

    Thanks
    Frank Albanello
    Sounds like something that Mythbusters might have an answer for!

    I honestly do not think that this can be answered unless you actually perform the test in question with the materials you have listed.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  3. #3
    Join Date
    Mar 2007
    Location
    Philadelphia PA
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    3,177

    Default Re: Which is stronger

    Quote Originally Posted by Scott Patterson View Post
    Sounds like something that Mythbusters might have an answer for!..
    Wouldn't they just want to blow it up?

    I'm always telling clients about how the Mythbusters blew up a water heater so they (the clients) might be more interested in what I'm explaining to them about the tpr valve.

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  4. #4
    Join Date
    Dec 2009
    Location
    St. Louis
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    35

    Default Re: Which is stronger

    Just thought someone might have some experiance with the strength of plywood as compared to sawn lumber or be able to direct me to the information .

    Thanks anyway


  5. #5
    Join Date
    Feb 2008
    Location
    Chicago IL
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    1,984

    Default Re: Which is stronger

    Don't know why you would want to know this. It isn't a realistic question outside of controlled laboratory conditions anyway. There are two many other variables that could fail besides the lumber or plywood pulling apart.
    - plywood could pull off of lumber instead of pulling apart; plywood will pull off of clipped nails, dusty ply or lumber would make the glue less adhesive to either surface
    - if the 2x has typical splitting or cracks, it could pull apart more easily but that doesn't necessarily speak to the strength of the 2x overall, just that particular 2x
    - how would you be gripping the plywood? a section could break off but the remainder could stay on the 3x
    Care to provide some construction context for this question?

    www.aic-chicago.com
    773/844-4AIC
    "The Code is not a ceiling to reach but a floor to work up from"

  6. #6
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: Which is stronger

    Quote Originally Posted by Frank Albanello View Post
    Just a general question:

    If you have a piece of plywood, glued and screwed/nailed/bolted to the same dimensions as a piece of lumber ie: 2x5....2x8 , does the plywood have more or less tear apart strength then the lumber ?

    (If you pulled on both ends of the built up plywood and the lumber, with the same force, which would come apart first ?)

    Thanks
    Frank Albanello

    If you glue plywood together to make up a particular dimension of standard lumber it is as if you are making a laminate beam which is much stronger than dimensional lumber. I am quite sure it will depend on the method of joining all this plywood. It would have to be under controls of some kind and the proper adhesive.

    I joists is a very good example. They can span greater distances and give less flex than dimensional lumber but that is not the type you are addressing.

    Over all. Given the right set of controls my answer would always be yes.

    Now go buy yourself some gorilla glue. Glue many layers together and start pulling, twisting and bending.

    Another example would be finger jointed 2x4s. take a standard 2x4 and a finger jointed 2x4 and try to bend them around a tree. Both will break in the dimensional lumber lengths before the finger joint will........Until you expose the finger joints to the elements. Then it may just fall apart.


  7. #7
    Join Date
    Oct 2010
    Location
    ventura, ca
    Posts
    63

    Default Re: Which is stronger

    Good Question...

    The answer is that no credible Professional Home Inspector would
    touch a question like that.

    It is an engineering calculation with a zillion variables.

    If you really want to know - build it and tear it apart.

    mf.

    Matt Faust
    Real Estate Inspector

  8. #8
    Join Date
    Mar 2007
    Location
    Mahtomedi, Minnesota
    Posts
    92

    Default Re: Which is stronger

    You may need to develop test parameters to determine how compare plywood to dimensional lumber. There are different grades of plywood and different grades and species of lumber, each has vastly different performance standards.

    Some plywood is amazingly strong, some not. Same for lumber.

    Fred Comb, ACI
    Mahtomedi, MN
    www.homeinspectionsofmn.com

  9. #9
    Join Date
    Mar 2007
    Location
    Oregon
    Posts
    2,365

    Default Re: Which is stronger

    My money would be on the plywood being stronger... if for no other reason, the lumber these days is just crap. I don't think you could find a piece without 10 knots in it. You're hard pressed to get a 2X4 at Home Depot that you can't break at some point with your bare hands.


  10. #10
    Join Date
    Jul 2008
    Location
    Snowbird (this means I'm retired and migrate between locations), FL/MI
    Posts
    4,086

    Default Re: Which is stronger

    It depends (on a lot of variables which you have not begun to address).


  11. #11
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
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    4,549

    Default Re: Which is stronger

    Frank, if you want to hang something from the ceiling, look into using steel, either threaded rods, cables/chains or strap iron. The weakness in using wood is in the fasteners, which will be perpendicular to the load.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

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