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Thread: Taking the bounce out of a floor?

  1. #1

    Taking the bounce out of a floor?

    I recently bought a house with a 2 story garage. the upper floor is 30 X 24 and open. the lower is divided into bays 20 X 12 with a 10 X 24 room on the back. The floor joist are true 2X6 on 24" centers. the garage is balloon framed with the floor joist nailed the outside wall studs and the centers resting on the dividing wall between the bays. the Floor itself is 1X6 shiplap planks
    The floor has a lot of bounce when you walk across it and I would like to get rid of it. I have been trying to decide on one of two ideas.

    1 remove all the wiring from the existing floor joist and install 2X8 resting on another 2X8 nailed to the existing framing and blocked between.

    2 add 1X6 boards to the existing floor

    I'm thinking #1 is the proper way to go
    Thanks for your help

  2. #2
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    It is not clear to me from you post how far the floor framing is spanning. If they are spanning 20' or 24' that is really far for 2x8. You'd be looking at 2x12 not even working per design calcs. You can check a span table to see what size required.
    Last edited by Kurt Cady; 05-22-2018 at 7:21 AM.

  3. #3
    the span would be 12'

  4. #4
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    Jerome

    What you do is going to be completely dependent on your intended use of this space. As is, it's really just for some light storage, and enclosed the area below. That is very light construction. Even for rough cut, balloon, style. My house and garage are also rough cut, true 2x's, and balloon construction, so I know what you're dealing with.
    What is the span of the joists? It seems as if it is at least 20'. It also sounds as if you have rough cut joists, if they are true 2x6's, and balloon construction.
    The only way to get rid of the bounce is to reinforce that floor, which means replacing, or sistering, joists to the existing joists. 24" on center is also an issue, because you're probably going to want to be 16" on center. You may not be able to do 16" on center, if your wall studs are 24" on center.
    At minimum you're doubling up the existing joists with sistered 2x8's or 2x10's, and putting down a staggered plywood, or engineered subfloor, creating an entirely new floor, and that would just be to remove the bounce. The 1x6's aren't helping you at all. They're making everything worse. You can put them back down on top of the subfloor.
    As I said, I have the same issues with our house, and when I went to the building inspector about replacing all of the joists and sub floor, I was told that if I removed the existing joists and installed new, I would need a civil permit, with an engineered sign off. If I sistered to the existing structure, I could do everything under a remodeling permit, and there would be no civil inspection.
    There are "rules" associated with sistering joists. There is a way to do it.
    To make that a load bearing floor that meets current building codes would take a lot more work.

    As I said before. It all depends on what you want to do with this space.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  5. #5
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    It takes a LOT of lumber to reduce bounce. For example, my next build has a 24x24 freespan room, which they want tile on. LP specs 14" I joists on 12" to do it. Your space isn't the same, but it's maybe an illustration. My current build is a remodel that has a 2x8 floor, balloon framing, 12' span, and a serious bounce in the upstairs bedroom. Ended up putting a beam in the basement under a new stair wall so it can be supporting, and adding a lam beam across to cut the joists and tie into. It massively helped, but I wouldn't tile it yet. Check out LP or Wereyhouser span charts, and use a L360 or higher to see what you really need.

  6. #6
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    Blocking or cross bracing spreads the load over several joists if done right, but your floor is way under built as it is. If you intend to use the second story floor for anything substantial you will need to re-frame it using 2 X 10 or 2 X 12 joists. You could add these between the existing 2 X 6 so you would have framing on 12" centers or just up against and joined to the existing 2 X 6. Their ends should be supported and not just nailed, so additional wall framing would be necessary too.

    Charley

  7. #7
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    In addition to adding more joist support, a double layer of plywood for the attic floor might also help reduce bounce. I agree with Charles that for frequent use of the upstairs, the existing structure is not adequate. I will add that you may want to consult with a structural engineer or very experienced local building resource to choose the best path forward.

    My shop has an upstairs...there is no bounce. But it's 12" I-joists on 16" centers spanning 23' with a 3/4" plywood floor. Rock. Solid.
    --

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

  8. #8
    Sorry, I seem to be as not as clear as I thought the first floor is divided in half so the joists only span 12 feet. I plan on the 2X8 in between each existing joist so 2X6 a 12-inch space a 2X8 a 12-inch space etc. The shop was built in the 40's and was a functioning wood shop upstairs until the old guy passed 9 years ago when we originally saw it it was filled with general machines.

  9. #9
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    Jerome

    If installing the 2x8's between each existing joist, still leaves you with 24" on center, you would be better off to sister them to the existing joists and doubling up on your thickness of each joist. Give yourself a little more "fat" that way.
    A staggered plywood subfloor still needs to replace those 1x6's to tie the floor together across it's face, and the cross bracing needs to be installed between the joists to further stiffen everything up.
    The floor of my living room is rough cut 2x8's on 16" centers, spanning 13', with two layers of T&G flooring. It still bounces.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  10. #10
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    Sorry, this is no help for your question, but it reminded me of once, when I was called to examine a Parsonage built before there were building codes. When I walked into the front door, a cat jumped down off the sofa, onto the floor, and the floor bounced like a trampoline, with many oscillations. The floor joists were 2x8's, 20 feet long, with nothing supporting the middle. A basement had been dug after the house was built, and any center support that was there, had been done away with.

    It shouldn't be hard to find span tables online.

  11. #11
    There is a lot of difference of strength in different species of lumber. If you are looking at using spf lumber, probably won't help much. Hemlock is a stronger species, used to be called Hem-fir, there is maybe one fir board in a pallet. If you were to find some yellow pine or douglas fir, you would add considerable strength. It is amazing how much stronger I-joists are than lumber, if you wanted to sister in I joists you would be amazed how much stronger your floor would be.

  12. #12
    Quote Originally Posted by Mike Cutler View Post
    Jerome

    If installing the 2x8's between each existing joist, still leaves you with 24" on center, you would be better off to sister them to the existing joists and doubling up on your thickness of each joist. Give yourself a little more "fat" that way.
    A staggered plywood subfloor still needs to replace those 1x6's to tie the floor together across it's face, and the cross bracing needs to be installed between the joists to further stiffen everything up.
    The floor of my living room is rough cut 2x8's on 16" centers, spanning 13', with two layers of T&G flooring. It still bounces.
    If I install between the existing 2X6's it would be 12" centers I am confused as to why you are saying it would be 24"? QAs for the 1X6 floor right now each one is toe-nailed to the existing joist and they are run at 45* to the joist I plan on using flooring screws into the new joists.
    Last edited by Jerome Sidley; 05-24-2018 at 6:30 AM.

  13. #13
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    Jerome

    Apologies, I misunderstood what you were doing, and for some reason was locked into a mental model of the existing 24" spacing, nailed into the studs on that same spacing. If you can get to 12" on center, that would help you significantly. I see what you're doing now.

    It's a lot of work, but you'll be much happier when you get done.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  14. #14
    I'm not trying to justify my idea just trying to figure out what others are thinking. I don't need a rock steady floor just much better than I have I can't afford to tear out and replace but would like more strength. When we originally looked at the house and I went into the shop I don't remember this much bounce I was thinking this morning if removing the PO machines has allowed the joists etc to spring back and if putting weight back on would help? Just throwing out ideas.

  15. #15
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    Jerome, If you go 12" on center with another 2x6 (LVL for stability), then a layer of 3/4" tongue and groove subfloor over the top, it will get better. Make sure the existing floor sheeting is screwed down really well before adding more on top, then lots more screws. Ideally you'd pull the existing board sheeting, and glue and screw a layer or TG sub ply to the joists, then add another on top, but it might be a major pain to do that. You could do another thing to help it by adding a plywood skin to the bottom of the floor (the ceiling of the lower room), but that is usually a major process.

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