I would like to mount a 100 lb heavy bag using a system detailed in the attached picture (FirstLaw Fitness Shock Mount). The system is designed to be mounted between and directly to 2 joists that are 16" on center with included lag bolts. My garage ceiling is covered with drywall with a bedroom above. I assume (hope) that the gas strut on the mounting plate will somewhat help with noise and vibration (no impact on load path), but my largest concern is mitigating unsafe loading conditions on the ceiling. I saw an earlier post where a structural engineer suggested not attaching the mount directly to the joist. Was this to provide mitigation for vibration/noise?

Can anyone provide a "safer" installation idea or are the instructions adequate? Based on an earlier answer, could I further distribute the load if I attached a 2x6 or 2x4 on the ceiling so that it runs under the floor joist for a couple of feet, do the same to the next joist over and then attach the mount perpendicular to and on the 2x6's? If this is acceptable, what size and length of lag bolts would be required since they would need to go through the 2x6 and into the joist? When attaching the mount to the 2x6's, would the lag bolts also need to go into the joist? And finally, if this idea provides for better load distribution/safer install, is there concern that it does require more holes being drilled into the joist?

If anyone has a better/easier/safer idea, I would be most interested. A diagram with dimensions would be great.

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  • Have you verified that your joists are 16" OC? Sometimes they are 24", and that would change your plan.
    – JPhi1618
    Mar 15, 2019 at 15:02
  • This is a Q & A with some useful answers : engineering.stackexchange.com/q/22610/10902
    – Solar Mike
    Mar 15, 2019 at 16:04
  • Voting to close. Questions remain unanswered and OP hasn't been back.
    – isherwood
    Dec 10, 2019 at 18:27

2 Answers 2


I wouldn't worry about doing structural damage to your joists with this mounting hardware. Realistically the 100 pound heavy bag won't generate any more wear and tear on the joists than a 100 pound kid upstairs jumping rope would. The shock absorber will even out some of the peaks and valleys of the dynamic loads.

If you really want to spread the load to more joists, sure you could attach boards to spread the load to more joists. I don't think it's necessary.

I would probably use 2-1/2" x 1/4" lag screws with full depth 1/8" pilot holes to mount this - nothing larger, possibly something smaller. That won't appreciably weaken the joists.

The most important thing is to locate the joists accurately and hit them as close to dead center as possible.


Following the instructions from the other post would be sufficient. Another method is to cut a 4x8' sheet of 3/4" plywood in half an fasten with 3" wood screws into the centers of your joists. Add the second half in the same fashion. After the two halfs are stacked on the ceiling you'll have a strong 3/4 + 3/4" 1-1/2" slab to fasten the bag hardware to.

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