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I recently hung an 80lb punching bag from a 2x10 in between joists (also 2x10) in my basement, essentially below my living room.

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The hook hanger is only off-center because I thought it might swing into the drop ceiling supports if it was too close. I now realize that is unlikely to happen after hitting it a few times and plan to move it more directly in the center of the added 2x10. However, when I stand on the floor above where it is hanging, I can definitely feel vibrations and noise when it's being hit. I used three GRK RSS structural screws (5/16" x 4") on each side, for a total of six screws.

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My idea is to add more 2x10 blocks in between the joists to the left and right of where the punching bag is hanging to brace against the swinging forces. Would this work to reduce vibrations or otherwise prevent any structural damage from occurring over time? Obviously my living room floor is more important to me than having this punching bag here.

Is there any other way to configure this for added stability? I appreciate any help!

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    The weight reminds me of a younger kid jumping on the floor, so I don't think there's a structural concern. Living rooms get designed for 40 psf live load, further putting my mind at ease structurally.
    – popham
    Oct 1, 2023 at 20:19
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    Conventional wisdom is that your extra blocking transfers load across more floor joists (the blocking has to be nice and snug), so that should give the floor in the bag's neighborhood more inertia and stiffen it up. It should therefore help.
    – popham
    Oct 1, 2023 at 20:22
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    The current block looks thick enough for such a short span that I doubt there's a significant vibration mode bouncing it side-to-side, but just in case you might pair it with another block attached to its side.
    – popham
    Oct 1, 2023 at 20:28
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    There's a length cubed in the stiffness of beams acted upon by a point load like that, so halving the beam's length will decrease its midspan deflection by a factor of 8. Adding a post would therefore work great, but I assume a post would be a nuisance at least.
    – popham
    Oct 1, 2023 at 20:35
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    The typical detail for your blocking is to stagger it so you can face nail them analogous to how you screwed that initial piece. No need to line up the ends.
    – popham
    Oct 1, 2023 at 20:43

2 Answers 2

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There's nothing to brace here, and you won't eliminate vibration or noise unless you use a dampening mount of some sort. The 2x10 block already prevents the joists from tilting, and the subfloor ties it all together.

Don't add more lumber. It won't do anything significant. You'd have to use some sort of elastic vibration isolation hardware, a la automotive engine mounts, to accomplish your goal.

Rubber washers won't help, either. Vibration will still translate through the screw. You need to decouple the movement of the bag from the floor framing with something elastic.

One strategy would be to use four of the springs like you have, mounted in a square, and brought together at the bottom like an inverted pyramid. This would provide lateral elasticity, which is what you're lacking now. It would also provide more vertical elasticity.

About your current hardware... Those little clasps aren't up to the job of holding that dynamic load. Look at the tiny pin connecting the swingarm. I don't care what the sticker said, use a proper carabiner or quick link. That mounting eye also looks like cheap import metal. I'd expect it to crack before long. Use a 5/16" screw eye or better.

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  • The rubber washers intervene in the load path between the load and the floor system.
    – popham
    Oct 2, 2023 at 16:47
  • Coupling the joists will increase the stiffness by up to a factor of three and therefore reduce the vibration amplitude by up to a factor of 3. Coupling the joists will increase the modal mass by up to a factor of three and therefore reduce the vibration frequency, a win from the standpoint of human perception.
    – popham
    Oct 2, 2023 at 16:56
  • Yes. The whole train of hardware is bad. The spring and swivel are purely cosmetic. A punching bag doesn't need a swivel, but if you want one, get a better one. Just replace everything with a good purpose-made punching bag hanger. You can go crazy with pneumatic damping, or get tunable vibration isolators, or just try to get one that mounts solidly to the brace, includes a good ball bearing swivel and a spring that is tuned for the weight of your bag. That should get you most of the damping you want. Additional home-grown isolation will probably have rapidly decreasing return on effort.
    – jay613
    Oct 2, 2023 at 17:29
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Your blocking idea with the adjacent floor joists will stiffen the bag's support and increase its inertia. This is a legitimate strategy. The blocking should fit snug enough where it's somewhat difficult to get it into the spaces. Stagger it from the existing block so that you can again fasten through the face of the floor joists.

Since adding mass will eat up the system's load carrying capacity, increasing stiffness is the best strategy if the blocking still proves insufficient, where your best option (without adding columns) is probably "sistering" another joist or two with the existing load carrying joists. They're painful to get in there usually, but 2x8s sistered to your 2x10s would be an option in your case.

You can add some rubber to dampen the vibration, but this is relatively ineffective for shock loading like you've got here. Once the vibration has gotten into the structure, isolation no longer dampens anything--the toothpaste is out of the tube. Remove that padeye from the block, install 1/2" thickness of 50 durometer rubber between the block and the entire bearing surface of the padeye, and then fasten the padeye again into fresh wood (or use longer fasteners in the old holes). Tighten the lag screws sufficiently so that the rubber is crushed to about 50% to 75% of its unloaded thickness.

There exist EPDM washers that you can buy. In addition to compressing the rubber between the padeye and the wood, you can stack these beneath a metal washer on the lag screw side of the padeye. If the rubber is too squishy for a big stack, insert a metal washer into the stack occasionally to stiffen it up. You could probably substitute these washers for the sandwiched rubber, but just be sure that the padeye can't rotate to impact the blocking in spite of your detailing.

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    Rubber washers will do nothing if the connection still contains a continuous steel screw.
    – isherwood
    Oct 2, 2023 at 16:27
  • @isherwood, it's not continuous. There are rubber washers in the load path now.
    – popham
    Oct 2, 2023 at 16:58
  • I don't see how from your description. Maybe revise to be more clear.
    – isherwood
    Oct 2, 2023 at 18:13

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