Gentlemen:
I’m working on an addition on my home, garage with a Master suite above. The second floor is comprised of I joists 16″ on center with a clear span of 22′ 6″ and L/480 deflection.
Looking for suggestions on stiffening the floor – 1×3 perpendicular on the bottom web ?
Replies
How deep are the I-joists?
Don't take advice from fortune cookies.
14", if I recall correctly. It's been awhile since I set them and I'm 50 miles away at the present time, so I can't get a quick measurement.
I can check tonite and let you know for certain. I do remember having the discussion with my local lumber yard (very helpful, not Lowes or HD) and informing the sales rep that I did not want a floor that "meets code" but something much stiffer.
I'm thinking about installing T&G hickory as flooring - not sure if that would have any impact.
Scott
Nothing you do will help 14" I-joists much at that span, except adding a beam or bearing wall. Adding some stiffbacks as you suggested in your first post might possibly make a difference. But I doubt it will very much.
I did a thread on Floor Vibration a while back which you might find interesting. While it's a bit too late to help out your situation now, it might help explain what's happening.
I think my life would seem more interesting with a musical score and a laugh track.
Wivell ---
1/2" ply glued and nailed to the top and bottom helps.
My span tables give 1/360 deflection for 1-1/2" x 14" I joists @40# load. That seems reasonable for a bedroom floor.
I use 12" I-joists @16" for 26' spans, but then I build different than most.
Boss Hogg ---
The vibration formula is wrong. The constant 386 should be 384. It comes directly from beam deflection formulas.
Plate deflection formulas give much better numbers.
Some of the paperwork I have uses 384, and some uses 386. Don't know why. But that's an awfully small difference anyway - Something like half a percent.
I think using L/360 for ANY floors is ridiculous, and doesn't accout for vibration.
Using 12" I-joists for 26' spans is nuts. I wouldn't want you building anything for me...Moroccan Proverb: The world has not promised anything to anybody.
Knowing that 384 is correct is important. It means I know the other problems with the work.
1/360 is code. That makes any floor reasonably safe.
I am not looking for work. I know how to correctly compute deflection and have good building techniques, so I can use the 1/360 tables for joists and produce floors that deflect less than 1/600.
Just an observation,
You have a real piss poor attitude around here sometimes. You often come across as rude, confrontational and a know it all on some of the threads I have read.
Not sure if you noticed or care, just an observationView ImageGo Jayhawks..............Next Year and daaa. Blues View Image
Before you comment on my attitude toward Boss Hogg, perhaps your should read Boss Hogg's comment toward me.
I don't try to be nice to those who swing at me first.
I'm with CAG - I think you're just a smart-a$$.
Know what ya get when ya cross a computer with a prostitute ???
.
.
A fÜckin' know-it-all.
George, its not just comments on this thread its others I have read.
I can't remember the exact one but at least once I have seen a reference to you saying the "people" here don't know what they're talking about etc.
you come across as very course.
View ImageGo Jayhawks..............Next Year and daaa. Blues View Image
wivell,
Why do you need to stiffen the floor above and beyond?
WAHD
[CMA] talk to an engineer. Just daydreaming, but if it were my house I might cross brace 4'OC w/1x3 and stress skin the garage ceiling like GeorgeR says, running the 8' edge of the PW parallel with the I-joists. Of course I might just be a wise-a$$ 12 yo. Who knows?
I know nothing.
SamT
Not sure exactly what your goal is or how you define "stiffen" but yes, placing strapping perpendicular to the joists at bottom is a recommended proceedure given by some TJI manufacturers. Boss has made a decent stab at making people aware of the varibles that influence vibration but I believe that for a bedroom, unless you do a lot of "excercise" up there, the vibration will be negligable. Vibration is a poorly understood concept and I have little to add scientifically beyond knowing that joist depth and total mass are two controlable factors. Based on my limited experience, 14" is not that bad, but Boss does a lot more of this than i do for sure.
Another factor on this is that you will need a fire rated ceiling in the garage to separate it from the master bdrm above. Two layers of sheetrock will help dampen vobration also.
Someone mentioned joists at 1-1/2" wide. I would have been using the next grade wider I-joist for that large a span. I presume you may have as well, depending on what your supplier speced for you. I don't use that minimum 1-1/2" joist for anything more than ten or twelve feet span.
Excellence is its own reward!