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Thread: Structural Floor

  1. #1
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    Structural Floor

    I’m about to start excavation on a 40’ x 28’ Shop. It will have a main level with a partial loft and (probably) a full basement. In addition to woodworking I also collect old machinery, which can be heavy.

    The floor will be wood for a lot of reasons, including comfort plus I build boats and need to nail down stems, transoms, and jigs, over a basement. The joists are 1 3/4” x 12” LVL’s and have been narrowed to 12” OC. The overall span is 28’ but there will be metal beam on 4 posts in the middle. So 14’ ish b/w support. Perimeter is concrete foundation wall and footers. Floor is 1” plywood (but under consideration for thicker).

    This has all been designed by an architect and engineer with my input on equipment inside, up to 2000 lbs in several areas peripherally plus there will be a tool cluster in the middle which might get up to 4000#. I’m told my design is “light industrial” specs.

    I would appreciate some other input from folks here, esp those who have similar shops w structural floors, making sure the advice I’ve received is good.

    Thx

    Jon

  2. #2
    Are you double sheathing the floor?

  3. #3
    they make a 1 1/4" t&g plywood.

  4. #4
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    I would consider a bridge crane while you are planning.
    Bill D
    Last edited by Bill Dufour; 07-28-2018 at 6:24 PM.

  5. #5
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    Thinking about maybe doing that instead. Two layers of 3/4”.

  6. #6
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    Quote Originally Posted by Bill Dufour View Post
    I would consider a bridge crane while you are palnning.
    Bill D
    Csn you explain this? Something for inside shop? I am planning on a overhead hoist on a trolley beam plus will have a 2 ton engine hoist for heavier things.

  7. #7
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    I could be wrong, but I believe that the purpose of the bridge crane would essentially be the same as the trolley beam, outside of being more flexible in position in the shop.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
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    Quote Originally Posted by Jim Becker View Post
    I could be wrong, but I believe that the purpose of the bridge crane would essentially be the same as the trolley beam, outside of being more flexible in position in the shop.
    Exactly. You can even buy a used bridge and design the shop width around that.
    Bill D.

  9. #9
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    That sounds like a good heavy duty design! With your joists on 12" centers you probably wouldn't NEED thicker than the 1" plywood (or as mentioned, there is 1-1/8" t&g available most places) but if it were me I'd go with two layers with staggered joints. And I did actually. My shop floor is 3/4" non-t&g on the first layer with a 1/2" plywood overlay and staggered joints (but all joints parallel with the joists do land on a joist, both layers). Even with joists @ 16" OC I don't feel/see any deflection, though it doesn't sound like I have any loads like you're anticipating.

    Also, don't automatically assume your LVL's (or I-joists, or PSL's) are arrow straight. I have seen more than not that had an ever-so-slight crown. The saving grace is they are normally crowned all the same direction and the same amount if they came out of the same stack. Whether by manufacturing or storage I don't know, but it something to be aware of.

  10. #10
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    Thanks Tim and others. Appreciate your advice.
    Last edited by Jon Snider; 07-29-2018 at 5:55 PM.

  11. #11
    Based on my observations working on construction sites for 35 years (mostly commercial sites but some residential) the 1 3/4” x 12” LVL @14" OC spanning 14' seems sufficient for your requirements. If the engineer has put his or her stamp on it, personally, based on the above, I'd be satisfied with that.

    My only question is with such heavy equipment, would 1" ply flooring be sufficient? I'd probably do double 3/4" ply, overlapping all seams, with something like construction adhesive bonding the ply subfloor to the joists and ply top floor to the ply subfloor. Unless you anticipate needing to get back under the floor for some reason.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

  12. #12
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    If you are worried about the floor, upsize the joists to 14". The engineer no doubt knows his stuff though.

  13. #13
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    A bridge crane has a pair of fixed rails (trolley beams) and a cross beam with the hoist on it. It allows you to move left and right as well as forward and back. It can cover an area, not just a line. It is more expensive and complicated but can do more. Depends on what you need.

    Span = the distance between the rails.
    More span covers more of the shop but requires a heavier cross beam and restricts where you can have anything tall or any power or dust collector drops.
    Since it transmits the load to the building closer to the sides it can reduce the overhead structural requirements. You definitely need your engineer to include any significant loads like this into the truss design.

  14. #14
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    You don't mention it but you are probably planning to instal X bracing or blocking between the joists. Blocking provides better support but it will restrict the stuff going thru the joist space. A 1 x 4 stringer on the bottom instead may work out but your engineer must approve.

  15. #15
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    Yup... two layers of 3/4 ... definitely w staggered joints.... In BOTH x and Y directions.

    No T+ G needed. just good Canadian or USA plywood.

    NO Import !!!

    Marc
    Last edited by Marc Jeske; 08-08-2018 at 11:11 AM.
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

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