I just had a house built and TJIs were used for the first floor joists due to the long span they run over. From the steel I beam running down the center of the house, to the outside foundation is about 17 feet.
When I sit on a stool at my breakfast counter over this span, I can feel the floor deflecting when anyone walks past behind me – and they don’t have to be particularly heavy.
There is no blocking or cross bracing on the TJIs below. Short of adding a wall underneath and ruin the open space in the basement, is there some kind of blocking between these TJIs that I can add to stiffen them up?
These are 12″ TJIs on 16″ centers spanning the 17 ft.
Bill
Edited 9/5/2007 12:10 am ET by BSartist
Replies
If you contact the I-joist manufacturer they will likely have some ready remedies for you. You are not the first person to ask this question.
>> These are 12" TJIs on 16" centers spanning the 17 ft. <<
FMOI, what is the width of the top and bottom flanges?
Personally I don't think blocking or bridging will help.
Hmm. Not sure and I'm not at the house to measure. They look to be about 2 inches or so.
I-joists that are 12" deep and spanning 17' shouldn't have much vibration in them. That's well within my comfort zone, and I'm pretty danged conservative.
Sometimes an undersized beam can make vibration more of a problem. Do you have the specs on your steel beam?
Have any of the I-joists been compromised by plumbers or HVAC guys?
It definitely feels to me like the joists and not the beam flexing. I don't have the specs but it's pretty beefy.
No HVAC or plumbing breaches. Just a hole for wiring in the middle of the TJIs. Maybe about an inch and a quarter or so in diameter.
Bill
Any chance we could get a couple of pictures?
A good plan violently executed NOW is better than a perfect plan next week. [General George S. Patton]
Absolutely. When I get home this evening.
Thanx!
I do have some very early photos if these help in the meantime:
http://bsartist.com/apploopdetailed/gallery06/pages/apploopframing_41.htm
http://bsartist.com/apploopdetailed/gallery06/pages/apploopframing_40.htm
These have ductwork and plumbing going in:
http://bsartist.com/apploopdetailed/gallery10/pages/IMG_7772.htm
http://bsartist.com/apploopdetailed/gallery10/pages/IMG_7775.htm
I still wonder about the steel. It does look fairly deep. But the distance between posts also looks like it's substantial.While you're taking pics, could you get the depth and width of the beam, and the distance between posts? Just to satisfy my curiousity if nothing else. I'm also curious about the brand and series of I-joists, if that's stamped on the side. A picture of that would be helpful.
Back off! You're standing on my aura.
The house is upstate but from the drawings, I see that the beam is spec'd as "W10 x 54 Steel I-beam" and the distance between is 18' 8"
One of those photos does show the TJI brand. Says "Silent Floor TH230"
Maybe you are right about vibration vs. deflection. I'm not an expert on measuring that and it does seem unlikely that a medium weight human would deflect those things. Seemed to feel like the floor was dipping under me a little but maybe imagination.
It may be important to note that kitchen tile spans over the steel beam. Starts about 4 or 5 feet to the "dining room: side of the beam all the way to the other foundation. A couple months ago, while the house was still being constructed, a crack DID show up in the tile. It was a crack down the center of 5 tiles (for a total of 5 feet) running in the same direction as the beam but a foot or so to the dining room side. I don't know if it was from settling or deflection. If the latter, I probably want to get this stiffened up before those tiles are replaced.
Man, that's one whopping hell of a beam. I ran it real quick, and it DOES work O.K. by the numbers. But it also shows nearly an inch of deflection under full load. I still think it's possible that it's contributing to the problem. If you have a mind to, you could put a temprary jack post at mid span and see if that makes a difference in the "feel" of the floor. .The strapping that some have suggested may or may not help - It's hard to tell for sure. But it doesn't take much to put one row of bracing down the middle of the span and see if the "feel" of the floor changes. You can always put it on with screws so it can be removed if it doesn't help.
An oral contract isn't worth the paper its written on
It might be just my eye, or tricks of the camera, but I'm pretty sure I see deflection in that beam in the photos.On strapping, it takes a full cover of 16" OC over the whole space to get the full benefits of making that diaphragm resistance to vibration and make all of them work together well.
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No that's definitely barrel distortion introduced by the wide angle lens. I know because I usually spend time in photoshop correcting it out of the photo.
I believe that some good blocking would help immensely. You do need to make sure that it's installed in keeping with the mfgr's instructions, though, to avoid damage to the joists.
Do you have drywall installed on your basement ceiling?
If not, I would try installing one or two rows of strapping (2x4, 1x4, 1x3, whatever) to restrain the joists so they do not twist.
My feeling is that some of your vibration (BTW- as Boss mentioned, the problem you're feeling is more likely vibration than deflection) is stemming from the joists being allowed to twist or squirm under dynamic loads. If you can tie them together so they are locked in plumb, your problem may be solved. It's quick & easy so worth a shot.
If you ever finish the basement and want to put GWB on the ceiling, just remove the strapping as the drywall will serve the same function that the strapping was.
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
I'm guessing there is no ceiling attached below. Actually sheetrocking the bottom of those joists can stiffen them up significantly. Ties all the bottom flanges and adds mass to resist vibration. What you are feeling is more vibration than deflection.
M
------------------
"You cannot work hard enough to make up for a sloppy estimate."
Strapping the bottom flanges of the TJIs as Jon and others have mentioned should help.
TJIs, being engineered, are fairly uniform in their make-up, so they reverberate more than stick lumber.
Strapping helps minimize the vibrations and can stiffen the floor a bit.
Mongo
So just to make sure I understand, do you mean just laying a 2x4 on it's flat up against the bottom of the joists and nailing it into the bottom of the bottom flange?
Or something more sophisticated like cross bracing in between them?
Thanx
You sir, are correct.Laid flat, fastened up into the bottom flange.
From experience,I can tell you that both strapping w/2x4 or drywalling the bottom help considerably in reducing this effect. If I strap them I glue & screw the straps on, 2 rows equally spaced for a 17' span. IMO, the straps work by spreading the deflection out over more joists(transferring some load). Drywall,on the other hand works by "preloading " the floor (Think of a drum, if you put your finger on a drum,then hit it with a stick, it will resonate far less than without that "weight"on it) I'm no engineer, just my "seat of the pants" opinion
Also you could have a bad joist or joists. Have someone above try to put point loads on one joist at a time while you look closely at the web/flange connection. I got one load that had some of the joists with the glue missing the groove. Didnt realize there was a problem untill finishing stage,factory engineered a fix but a major PIA it was.
When you feel the deflection, probably what you're feeling is a rocking motion. Eg, if there are two joists below, A and B, and if your stool has two legs between A and B and two legs on the far side of B, when someone walks along and causes A to deflect the floor will tilt and you'll feel the stool pitch towards A. We tend to be much more sensitive to this side-to-side motion than up/down motion.
Strapping will help this somewhat, but blocking is more effective. By tying adjacent joists together with blocking the dynamic load is spread to the two adjacent joists, reducing the total bounce by a factor of 2-3. But in addition, by making joists move together rather than independently the degree of tilt and subsequent side-to-side motion is greatly reduced.
I think you are correct about the rocking motion.
As far as I understand it, there are some restrictions in terms of blocking between TJIs in terms of how you can or cannot nail into the flanges.
What type of sheathing was used? Sometimes I find on 16"oc, sheathing flexes if not substantial enough.Another thought too, Test in different areas of the room to see if its just 2 or 3 joists where you are sitting or it's the whole room. This way you can centralize the problem or you can see if it's the deflection of the joists in general.
http://bsartist.com/apploopdetailed/gallery06/images/apploopframing_49.jpgIt is plywood decking, but I can't tell whether 3/4" or 5/8"
The wall sheathing was OSB.
It looks like it was a pre-framed assemble on site with telehandler job
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The plan calls for 3/4 inch T&G plywood. Not sure if it was glued but I have no squeaks.
Nice house, neat design.. especially the loft.. very unique
Thanx much!
Everyone has asked the questions I would--but one.
What subfloor is on the TJI?
Was the subfloor glued?
I've seen exact-to-spantable floor framing with absolute junk put on for a subfloor. This can be tough sledding. Framing beefed up to l/480+ with l/120 or l/240 subflooring on it is a hard fix.
All I can tell you is that it's plywood subfloor
I looked through the rest of your photo spread navigating sideways from those links. Looks like the framers did a bang-up good job there. Saw lots to be impressed with, including the view.
I but I did also catch a glimpse at what could possibly be a part of the problem.
Make no doubt about it, that adding strapping everywhere under that floor at 16" OC will help with vibration in open areas.
Bu5t6 what I am seeing is that the way things are framed on the first and second floors, there is a lot of point load transferrance to small locations, some not directly in line with one another. With right calculations and squash blocks in the right places, all may be fine. There is a lot I can't see and don't have a full set of prints to review, but it might be worth your while to have the original engineer review things with this and the vibrations in mind.
Here is an example of what I see -
http://bsartist.com/apploopdetailed/gallery06/pages/apploopframing_18.htm
The beam in this photo lands at the left side of stairwell on a short wall.
http://bsartist.com/apploopdetailed/gallery06/pages/apploopframing_39.htm
if that same stairwell is the one showing in this photo in the cellar, then there is no squash block supporting that point load there, and the point load is a few feet away from where the load supporting post is under the beam.
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http://bsartist.com/apploopdetailed/gallery06/pages/apploopframing_52.htmHere is another example of hpw a tremendous amount of load can be all transferring to one location.
Uneven loading on beams can make the calculations get difficult - definitely different from even loading in normal charts and definitely over my head where I call a good engineer.If this was a kit home of some sort, have it reviewed by another engineer of your choosing.
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That's an outside corner. You are actually looking at 2x6 framing arranged at a right angle so it's not at thickly packed as you might think. Hard to tell from a 2D photo though.
BTW, that cut off lalli column was not supposed to be installed anywhere :-) I suspect it was a mistake of somesort.
BTW, you are correct that these were pre-built wall panels that were then erected on site. But not a kit home. Actually due to the nature of the process, the plans are gone over quite a bit by the fabricator so they can make sure that the panels are totally accurate. I don't know if they do load calcs but I know my GC had his engineer take a look at some of these load calcs awhile back.
Here is another picture which gives a better frame of reference for viewing that corner detail (the one with the writing on it).
http://bsartist.com/apploopdetailed/gallery06/pages/apploopframing_12.htm
I am very impressed with the house overall, and didn't mean for any of my comments to be taken as negative criticism, just pointing out clues that appear to me that could possibly be a part of the problem you have. That was why suggestion of an objective outside engineer. Definitely you need to get support under that one beam end.You should be able to tell which plywood was used from notes on the plans. 3/4" glued makes for a much stiffer floor system than 5/8" nailed only. Given the overall good work, I can't believe they would have failed to glue the floor, and you would probably have a few squeaks already if they hadn't. The reason others asked if you could measure the size of the i-joist flanges is that there are three or four different types of I-joist, The weakest would be 1-1/2" wide and have a web that is 3/8" thcik, while the next would be, I believe, 1-3/4" with 1/2" web. Then about a 2-1/4" flange with a 1/2" web. That is all frommemory but the point is that in the same height i-joist, you get differing onfigurations of materials to make stronger joists as needed. Boss wanted to check his figures with the exact type joist you have in the house
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No criticism taken. I appreciate the help and interest! I wasn't defending, just clarifying. I've not paid the final invoice yet so I would rather catch things now.
Thanx for the compliment.
The stamp on the joist said it was a 230 which I think defines the spec of the flange but when I get up there this weekend I will measure it.
Interesting post also on the deflective joist theory. i will check that out as well.
By the way, more up to date photos of the project can be found at the URL's below. Not sure if there is anything in there that shows more floor system detail
http://bsartist.com/house
http://bsartist.com/heroes_loop
Think this might have anything to do with it?
View Image
Joe H
It is hard to see in that photo but actually that load is sitting on top of a four sandwiched 1 3/4 X 11 7/8 flush LVL. Which amounts to a 5 inch wide beam there. It is not riding on the TJI
Unfortunately the original engineer passed away back in June but I had been over this detail with him before the house was built. What other examples of that have you seen in the pics?
I did read the manufacturers specs for the TJI and it looks like there might be a recommendation in there to have web stiffeners over the I-beam. They are not installed.
I did see a very glaring problem which I found it hard to believe was related to movement when walking. But it MUST be fixed anyhow (and soon I think). The attached photo shows the other end of that very LVL which rests on a short wall above the foundation. In my view, there should be a hell of a lot more packing under that LVL. You can even see the top plate starting to sag. The dining room in question is to the right of this LVL. But I don't feel the bouncing when people walk over the LVL.
>>IMG 1614.JPG
That's not an *entirely* unsupported point load but I'd throw 3 more studs under that pronto. How'd the inspector let that one go?
"I did read the manufacturers specs for the TJI and it looks like there might be a recommendation in there to have web stiffeners over the I-beam."
I've never seen such a recommendation for I-joists. There would definitely be a requirement for squash blocks over the beam *IF* there was a load bearing wall above it. But it doesn't sound like that's the case?
You're definitely correct that the LVL needs some studs under the end of it.
If you don't lay down, no one can step on you
I am referring to the top right of page 9 in this document:
http://ilevel.com/literature/TJ-4002.pdf
That's a new one on me - I've never seen an I-joist manufacturer call that out before. I can't imagine what purpose it would serve.
Appeasers believe that if you keep on throwing steaks to a tiger, the tiger will turn into a vegeterian [Heywood Broun]
By the way, at the rim joist, there would be a bearing wall above so I am thinking that squash blocks should have been installed there but they weren't. Unless the rim joist is made of a material that makes this moot.
That's right... You don't need squash blocks where you have an LVL or LSL rim joist.
Most brands of rim joist are designed for something like 2,000 PLF. So there's no need for squash blocks where the rim board is.
Hope he didn't use 2x12 dimensional lumber.
"Hope he didn't use 2x12 dimensional lumber."
I doubt they would have. 2X12 lumber is a different depth than I-joists.
If you can get a peek at the rim board you should be able to tell pretty easily. Most rim board looks sorta like OSB. The rest looks like plywood.
Don't give up - Even Moses was once a basket case
Folks,
Here is an update...
The rim joists are from the TJI manufacturer and are LSLs. So no squash blocks are needed. That's good news.
I am starting to think that maybe the lion's share of what I am feeling is vibration. Maybe a little deflection. I am told that I should expect some amount of deflection over a 16' span with TJI 230s. I might try some stiffening with strapping as you guys have suggested. At the end of the day, it's not HUGE deal anyway.