I found an email I wrote back in 2005 to another engineer about a
floor he was designing
but the most important thing I found was this link to a Canadian
The section about Vibrations from Walking is most applicable,
particularly the last two paragraphs.
If you really want to reduce that vibration "go big" on the sister
joists...... like ~ 2x12 engineered timber.
But you'll lose ~5" of room height. :(
Ralph's comments are right on target, I cannot emphasize too strongly
that this could generate problem that dwarfs your design fee.
Talk to the customer (end user ideally).
This really could be a problem downstream depending on the room usage
& their perception of the floor performance.
I highly suggest reading
Canadian Building Digest
CBD-173. Floor Vibration
I've done a fair amount of dynamic floor vibration testing & once
people get sensitized to it, it can be a real problem making them
I suggest forgetting about span/360 or span/whatever
deflection less than 1/16" under a 220 lb load is a good check. Also
joists at 12 o/c are much better than 16" o/c. Blocking is generally
not effective in achieving load sharing for vibration loading.
I'm not exactly clear on your floor system layout
You've also got to consider the dynamic response of the steel beams in
conjunction with the timber; the floor system as a whole. If the
customer is involved, has informed consent & is aware of possible
consequences of the "cheaper" solutions you're much better off.
To prevent vibration you need stiffness or mass; your choice.
Bob, thanks for all the info you've put up. I could afford to lose a
little ceiling height, (it's 8'4" now). But it's not all that GREAT big
of a deal. Also, my hvac and electrical is all finished, and i have a
great big sun pipe coming down through there, so I can't sister EVERY
joist. If it were before all this, I probably could have gone to a 10
or even 12" sister. It's just the two of us living here and the one
room above is our bedroom and the other side of the upstairs (no
partition) is her sewing room. There'll be no dances going on up there
or kids running around.. LOL!
remove the "not" from my address to email
If you can loose a little ceiling height, how about a small beam
perpendicular to the joists right down the middle, maybe a post in the
middle could make it a very small beam? That would make things really
solid and oh so much less work.
When I paid a structural engineer to confirm what I already suspected was
true, he advised, 16D CC nails 16" OC, 3 in a vertical row and 2 in the
middle of the OC repeated on the other side in an alternating pattern. This
was BNG (before nail guns) and I drove every one of those suckers by hand.
In oak I would pre-drill with a 1/8" bit because of splitting hazard.
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