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Thread: To Glue or not to glue

  1. #1
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    Default To Glue or not to glue

    I am building a picnic table out of some old 3/4 inch by 3 1/2 inch fir flooring. Gorgeous stuff, 16 to 20 growth rings per inch. It will be about 10 planks wide and I plan to put four full width cleats across the bottom side. The question is, should I edge glue the tongue and grooves or just rely on the cleats and screws? I plan to lay on several coats of finish and it will be supported by a pair of salvaged folding metal legs. Oh, not that it matters but it is about six feet long.
    Thanks for any ideas.

  2. #2
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    Default Re: To Glue or not to glue

    All the picnic tables I've seen have 1/8" - 1/4" gaps between the top's boards. I'd rip the tongues & grooves edges off, then put a small - 1/8" or 3/16" radius on the top surface edges. Then go with the cleats & screws.

  3. #3
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    Default Re: To Glue or not to glue

    I think edge gluing TnG flooring would defeat the purpose and advantage of the T n G.
    That said, picnic tables are not built of TnG ...rainwater...
    So, Will this table sit in the weather or will it be under one of those popular HGTV semi covers ?
    bruce

  4. #4
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    Default Re: To Glue or not to glue

    You must let the table top swell and contract without constraint. Forget the glue, leave gaps between planks at stated above. Cleats on the bottom are fine, but they should be in slots, not tight holes. Set the cleat ends in a bit if you don't want them to stick out when the top shrinks.

  5. #5
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    Default Re: To Glue or not to glue

    If there is any cross-grain construction it will explode out doors.
    No glue and slotted holes for the head end of fasteners wherever there is cross grain i.e. a 'cleat'.

  6. #6
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    Default Re: To Glue or not to glue

    Sorry, I gave some bad info. Yes a table to use during a picnic, but it will not live out doors.
    It will live in my shop as an additional work surface when needed, folding metal legs will allow it to "disappear"
    when not needed and easily be transported out to the yard when we have a cookout.
    Sorry, I should have been more clear.
    So, edge glue or not?

  7. #7
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    Default Re: To Glue or not to glue

    Sure then.Indoor table.

  8. #8
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    Default Re: To Glue or not to glue

    Quote Originally Posted by wizbang 13 View Post
    Sure then.Indoor table.
    Thanks Bruce, I guess I will edge glue it.

  9. #9
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    Default Re: To Glue or not to glue

    It's still going to move with seasonal humidity, so don't glue the cross cleats and use slots instead of holes for the screws.

  10. #10
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    Default Re: To Glue or not to glue

    If you keep the t&g joints but don’t exclude water, The inside of the joints will stay wet and encourage decay. Fir flooring is fairly decay resistant, bit I think you’d be pressing your luck. Expansion of the panel when wet will require fastening that tolerates motion. Needs slots of some form.

    If glueing the t&g joints and using a permeable (oil) finish, I’d worry that moisture cycling will gradually peel the glue joints apart. A truly impermeable finish would work.

    A third possibility is glueing the t&g joints tight and encapsulating the whole panel in a fiberglass sheathing, all sides. THis requires that the encapsulation be effective and that the glass and its bond are strong enough. I’ve made foils made of laminated Douglas fir sheathed with glass or carbon that have held up. Apply the glass on the bias so all its fibers are constraining the wood and use a UV resistant resin like West System 105/207 and a UV filtering finish on it.
    Last edited by JimConlin; 02-18-2021 at 08:23 AM.

  11. #11
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    Default Re: To Glue or not to glue

    Twenty years ago I glued up a 2x6í floating door panel from Doug fir t&g flooring. Itís as good as the day I made it. Functionally itís no different than a butt joint glued panel with all the limitations and advantages there in.

    Fasten your cleat in the middle through a hole and slots on either side, store indoors and you should be good to go.

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