sistering joists

[Steve Barker]

just for informational purposes, the flooring upstairs is 1x6 yellow pine T&G 90 degrees to the joists. Same age as. The ceiling downstairs will be 1x4 pine T&G (painted) so i won't get any benefit from that either. I'm mainly just not wanting the china cabinet upstairs to sound off (as bad, i know i won't eliminate it entirely) every time we walk across the bedroom or sewing area.

[DD_BobK]

e:

Steve-

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 report

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. :(

Robert Kazanjy

4/5/05 to seaint Dave-

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 happy.

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.

cheers Bob

[Steve Barker]

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!

[Tony Miklos]

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.

[Steve Barker]

I really did consider that option, but there's really not that much UNDER the floor (and no access) to hold the posts. PLUS, one of them would be dead center of a window.

[bob haller]

i would sister to a steel plate...........

[Steve Barker]

that was my first plan over a year ago, but not worth the expense and hassle of procuring (and drilling) the the plate(s) for no more than i'm trying to gain. Thanks for the suggestion.