I visited a home under construction recently to gather a few final measurements for our cabinetry designer.
As I was leaving and walking across the “Great Room” floor, I noticed that it seemed “bouncy”.
I went down to the basement to to a visual inquiry. 9 1/2 in I joists, 12″ on center, I’d say no more than 16′ span. (I paced of 5 strides) There were several rows of blocking, cut from yjr same material. I believe there were at least two or three rows.
Went back up stairs and began jumping up and down……….hmmmmm. Lots of deflection. Very bouncy and lots of vibration.
I have zero experience with these types of floors.
Teach me something.
Eric
Replies
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Be taught.
Joe H
Gained weight did we?
Spheramid Enterprises Architectural Woodworks
"Success is not spontaneous combustion, you have to set yourself on Fire"
Even the lightest 9-1/2" I-joist at 12" oc is rated for a 16' 7" span - IF it is surfaced with glue-nailed Sturdifloor. A nailed-only subfloor reduces the allowable span by 1 foot.
This, however, will meet code minimum requirements for 10 psf dead load and 40 psf live load uniformly distributed, which allows a little more than 1/2" deflection for a 16' span (1" in 360").
It's always a good idea to design beyond code minimum. And code does not take into account frequency of vibration, which is what makes a floor feel sturdy and not rattle the china in the cabinet.
Floor frequency of vibration (which is combined floor joist and girder frequency) should be greater than 15 hertz.
Joist Frequency (Fj) = 1.57 (gEI/ Wd L3)0.5 = 1.57 (386EI/ Wd L3)0.5
= 30.85 (EI/ Wd L3)0.5 [g=acceleration of gravity = 32.174 ft/s² = 386 in/s²]
Girder Frequency (Fg) = 30.85 (EI/ Wd L3)0.5
System Frequency = ((Fg2 x Fj2)/(Fg2 + Fj2)) 0.5
unacceptable < 11 marginal = 11-13 acceptable = 15+
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