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Thread: Bouncing floor

  1. #1
    Join Date
    Feb 2009
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    Default Bouncing floor

    When they put an 18 x 18 addition over the garage they installed 2 x 10 floor joists to span 18 feet, instead of what should have been 12. The floor bounces when you walk on it.
    I want to make a wood beam (osb?) to cut the span in half- any reccomendations?

  2. #2
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    Default Re: Bouncing floor

    a couple of questions, did they install cross bracing between the floor joists? is the orientation of the joists over the garage conducive to installing a lally column in the garage to support the beam you want to put in? this could make it a cheap and easy job. a little more info would be great.

  3. #3
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    Default Re: Bouncing floor

    The area is 18 ft square with the joists running at right angles to the doors (two eight foot doors with space between for a post)
    I don't think they put bridging between the joists. they are on 16 in centers. Sort of. they didn't remove the existing 2x8 joists for the ceiling that were on 20 inch centers, but nailed the 2x10's to the existing ones. These guys were so sharp that they were using 12d nails instead of 16d "because they were easier to drive".
    I read the article about sistering to the joists but don't know if that would be enough to solve the bounce.
    A steel I beam (at right ange to the joists) would be one solution, but weighs about 12.4lbs a foot, and would be heafty lift. 220lb plus.
    My brotoher in law is a registered engineer and suggested this solution. I was looking for something I could do by myself. The sistering plus a fabricated beam may be just enough.
    I don't want to put a post in the center, I use the space below as my wood working shop. the 18ft span may be too much for a fabricated beam (too deep).
    Last edited by Willieb; 02-22-2009 at 01:32 PM. Reason: added info

  4. #4
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    Default Re: Bouncing floor

    cross bridging between the joists should stabilize it alot. maybe even enough to make you happy with it. that being the easiest/simplest solution why not try that first and see how it goes. it should have been done in the first place. if it doesn't solve your problem then you can entertain the idea of a beam and it the cross bracing helps alot, maybe a small beam will solve the balance of the problem.

  5. #5
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    Default Re: Bouncing floor

    You could also sister " steel plate to the joists. Drilled and nailed every 16" top and bottom.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
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    Default Re: Bouncing floor

    If I were to do the sistering with 3/4" plywood glued and nailed to the joists would a single strip (on each one)of 8ft plywood be sufficent, or would I have to do more than the center 8 foot of the joist? CD plywood or OSB? Epoxy? or yellow gule?
    And of course following with bridging.
    On the bridging, what materials to use, 2x6? or "x" brace with 2x4? I have seen a commercial steel brace, assuming that they could be retrofitted.
    With this done, could see what results are obtained before making a decision on additional beams.

  7. #7
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    Default Re: Bouncing floor

    for bracing you can use 1x2 or 1x3 strapping, it doesn't take alot to make a big difference.

  8. #8
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    Default Re: Bouncing floor

    Quote Originally Posted by MLBSF View Post
    for bracing you can use 1x2 or 1x3 strapping, it doesn't take alot to make a big difference.
    So, that is steel strapping?
    What about 2x4's between the joists? square cut on ends between the joists at the bottom or lower half -or x braced?

  9. #9
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    Default Re: Bouncing floor

    i was talking about wood cross bracing, using 1x2's or 1x3's.....i bet you'll be surprised how big of a difference they make, might not solve the entire problem, but they will make a very big difference.

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