???how to straighten a bowed I-joist ???
I’m laying I-joists across a 13 ft. space for the floor above. There are about 14 of them and all of them are dead-on except for one which ‘humps’ up to a high of about 1/4 to 3/8″ above the others at about mid span. this has me stymied. I’ve thought of shaving some off of the few inches that it lays upon the top-plates at either end in order to lower the entire length some … but still the bow would cause some problems. Also been wondering .. better to have the above subflooring go down onto a dip? or to have the ceiling below go up to the indention? If the ‘hump’ is ‘down’ then the sheetrock below will have a problem. Aaarrrghhhh! Any suggestions? Is there a way to use clamps or whatever to straighten it out some? I don’t want to ‘send it back’ since this will mean shutting down for a week or more with the holiday coming. So .. wondering how to use it somehow since to continue and leave it out and try to fit it in later seems impossible.
Any ideas at all of how to make best use of the piece … how to deal with the situation … much appreciated.
thanks!
T.
Replies
Flip it upside down and strap your ceiling. Layout your strapping to avoid the hump.
dp,
I don't get it. whaddaya mean 'strap the ceiling'?
Also, if you are suggesting turning the 'hump' into a 'dip' ... would you shim or somehow 'fill' that dip before sub-flooring goes down?
but again .. 'strap' the ceiling?
thanks,
Terry
In New England, it is common practice to run strapping across the ceiling joists and install the SR or blueboard right to the strapping. "Strapping" is 1x3 furring and is available in lengths from 8' to 16' in 2' intervals. It's nailed to the bottom of the joists at 16" OC with a pair of 6 or 8D ring shank nails per joist.
The use of this system has been debated countless times here at BT, so I won't go into any of that. Basically, some say it is a waste of time (those who don't do it) and others say it has a variety of benefits (those who do it).
So I suggest that you flip the joist upside down "crown" down. Shim the dip in your floor as needed. And install strapping on 16" centers to the bottom of your joists (ceiling). I don't know how the space underneath the floor is broken up, but you will only need to strap the room where the hump is located. Lay your strapping out so that the hump falls inbetween two courses of strapping.
Just one possible solution. I'm sure someone else here will offer another.
Personally.... messing around with the flange of an I-joist is sacriliedge to me. You just don't do it. And I believe (but it's just my opinion) that trying to force the crown out of the joist will be an exercise in futility as you will be trying to accomplish the very thing that the joist was engineered to resist.
That being said....sending it back for another is still the best solution. However, I certainly understand schedules and deadlines and sometimes you just have to play the hand you get dealt.
View Image
Edited 6/30/2006 7:22 pm ET by dieselpig
thanks dp ... great reply.
the deal is that my joists ARE 16OC so that would mean a 32" gap unsupported on my gypsum ... or .. ???
I thought of placing it hump-up and hand planing it (?) .. sounds like a ridiculous pita but just trying to brainstorm ...
you're right, of course, about trying to beat the joist engineers at their own game by 're-training' it back to straight somehow.
Not sure now what I'll do ... pisses me off at Louisianna Pacific.
thanks again,
T.
Strapping goes perpindicular of the floor joists.
Find your hump in the ceiling and start your layout there each way 7-1/4 each way to the edge of each strap for 16 OC spacing.
It hides alot I do it alot. Probably not as much as DP though.Can't you hear the violin playing your song.
does this mean to run that strapping right up to the humped board and then discontinue it for the hump to run through and then REcontinue it just on the other side? Also ... could you use 1X2 on it's side for this ... broad side to the bottom of the i-joists? Then you'd only lose 3/4" of ceiling heighth ... i've only got 8' on these ceilings.
dp -- i get yer hesitation on the plaining .. i'm just thinking out loud about it .. trying to find my way out.
thanks-
t
Sorry, it must have been hard to see the detail in that first picture. Here's another:
View ImageView Image
are those 1 1/2" or 2 1/2" flanges?
I forget now... but they look like BCI 600's.... that'd be a 2 1/2" flange.View Image
they look like 2.5's to me too. I'm only spanning 13 feet with 9 1/2 high joists but the flanges are 2 1/2" When my architect/friend came by and saw them (he had called for 1 1/2") he said, "Dayam! Are you planning on storing ceiling-high loads of brick in this place!?" But I like the solidity of the 2.5's. (except when they're humped!)
t
What Stilletto said. Strapping is run perpendicular to the joists. Look, it's not the only solution... I'm just trying to brainstorm here for ya. Like I said... I'd think twice about planing the flange down. I might be a big 'ole chicken, but I'm just not interested in explaining to my insurance co, why I worked over that joist. Maybe that's the business man in me. The carpenter would probably say, plane it down.... but I really can't, in good conscience, recommend that you do that.View Image
Strapped I-joist ceilings:
View ImageView Image
wow ... beaUtifull! just saw the pic after my last posting.
DAMN but new constrruction is a BEAUTIFUL thing!!!
Picture's definitely worth a thousand words ... clears it all right up to see that. MUCH appreciated!
Though I must say ... I don't, offhand, see the 'need' for it in cases other than a specific problem like mine that may benefit from it. But then you said that there were long discussions on the pro's and con's of this that I never noticed here ... so .. there must be reasons for it's doing that i don't see.
gorgeous pic!
T
Whoops... you and me are posting to each other seconds apart.... sorry for being redundant with the pics.View Image
haven't you heard of crowning joists
RTC
haven't you heard of crowning joists
Geez RTC.... thanks for the Framing 101 refresher course. Any other gems to add to the discussion?View Image
you would be surprised
rtc
Take a piece of 2x stock and cut some tapered shims.
Newbuilder,
I'd probably get a replacement, if I had time.
I usually wouldn't have time if it was conventional joist but if it is I joist, I might have an extra day because they take so long to sort and install. If I noticed it early in the game, I probably could get a replacement shipped.
Most likely, I wouldn't have time. In that case, I'd probably call the lumber supplier and have them ask what the fix would be if I shaved the top. I'm fairly confident that the engineered fix would be pretty easy and straightforward. They probably would only require you to nail on a 2x4 x 8' long on the flange that has been shaved. That in itself isn't a very hard thing to do.
If they told me that I couldn't shave the Ijoist and add the "fix", I'd probably just rabbet the plywood and add some nailing scabs to each side of the joist. This fix would also be quite easy and require perhaps ten minutes time, but would be less desireable than the first fix suggested.
The last thing I would consider would be strapping. I'm not fond of nailing up support members with nails in withdraw and the entire idea seems a lot more troublesome than the two ideas that I first mentioned. IF I did have to strap the ceiling, I'd probably retire instead.
blue
blue,
sounds good ... but could you pls. clarify this with a little novice-speak?
"If they told me that I couldn't shave the Ijoist and add the "fix", I'd probably just rabbet the plywood and add some nailing scabs to each side of the joist. This fix would also be quite easy..."
I sorta like the idea of shaving it too ... I guess a hand-plane(?) I like to work with the dealt hand and do what I can with it. I DONT wanna go through the hassle of return and re-order.
thanks!
T.
I was taught that you never never ever shave one of the flanges of an I-joist. The flanges and the web are a system engineered to work together under load; top flange working in compression, bottom flange in tension and the web acting like the diagonal braces between top and bottom beams in a bridge truss. If you weaken part of that system by shaving the top flange, you weaken the whole thing - same as cutting into a roof truss. Can't your supplier provide a replacement out of inventory, perhaps a longer one that you could cut to length?BruceT
If you weaken part of that system by shaving the top flange, you weaken the whole thing
For every weakening, there is a fix. The engineers will easily spec something.
Since the top flange takes a compressive load, it seems to me that if you place the hump up, shave it down a bit, then glue & screw the subfloor on, there wouldn't be any issue. The subfloor firmly affixed to the top flange and attached to the other joists would more than take care of the compressive loads.
I'm assuming the amount removed would still leave some beef over the top of the OSB vertical web.
On the other hand, if it's only 1/4", you could make it a dip, and put some extra glue on the top to fill the gap. Even without strapping it, the ceiling below probably wouldn't really show it.
Like Blue, I'd suggest trying to get a replacement. I've never seen a crowned I-joist, and have to wonder if it's defective. One of the big selling points of I-joists is that they're straight and have consistent depth. Something's wrong with this one.
Streakers repent - your end is in sight.
So funny you mention about the crowned I-joist. They are out there all the time. Maybe it's because i've been framing in MN. It seems to be ironic that furring strips need to be put on the bottom of engineered joists so that the ceiling is straight. Every person in this "room" has parents that have houses with regular 2X material as floor joists. Most of us will think of those houses as being built well.Doug Fir is the way to go. If you are going to furr down the floor joists to keep the ceiling straight, use doug fir as the joists. That way the ceiling below will be flat and the floor won't bounce like an engineered floor will.even a stopped clock will be right twice a day
I sorta wish now that I'd just gone with 2X12 standard fir joists instead of all this i-joist bullcrap. maybe I'll finish up with those.
T.
Newbuilder,
I have to say that we've used 2x12 for floor joists. It makes everybody's life more difficult, drywaller, taper, finish guy if he runs crown.
You will nearly always get crowns 1/4" or larger. 11 7/8" I-joists are the way to go, even if there is a small crown (1/4" or less).
They are lighter, typically require a larger o.c spacing (vs 2x12s 12" o.c.). I just don't see what the problem is. But then I'm a framer and am used to lumber with 1/4" crowns :=)
thanks, Tim,
I was more or less just 'thinking outloud' in the midst of things.
Sounded fun to try it the old fashioned way ... the way all of our houses were once so well built. My own house, built in 1926, is SO well done. It's a craftsman (sears) bungalow and when the house inspector came through when I was looking at it to by 12 years ago, he said he's never seen a house so old so well built. I love it.
come on up to the top of the tower when I get it done!
thanks -
T
This pic shows the plywood with a plow cut into it to accept the higher than normal I-Joist. If you split the plywood joint on the joist, it would be a rabbet, rather than a plow.
Basically, you are just flipping the sheet over before you lay it and taking out enough material to allow the plywood to lay flat. It's a very basic and simple process and I've done it numerous times over the length of my carreer.
I think Boss touched on something in his last post that warrants further thought. You should determine why this particular I-joist is humped up. If its a manufacturing defect that doesn't alter the strength, then I would just do the fix. If it is humped up because of structural damage to the component, then you need to also deal with that engineered fix.
Out in the field, we sometimes can't afford to wait for answers. I'd visually inspect the joist looking for signs that it has been compromised. If it's a minor issue, I'd install it and call for an engineering fix. If it can't be fixed, they'd just send out a replacement joist and I'd sister it.
Get the thing sistered before they run the mechanicals!
blue
Would it be a criminal hack thing to do to just go get a 2x for that joist replacement?
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"Would it be a criminal hack thing to do to just go get a 2x for that joist replacement?"Yes it would. You can't replace it with a 2x because a 2x will shrink and the I-joist wont.You can't mix and match I-joists with 2x material.It's like when people ask to use a 2x12 for a rimboard/box when using I-joists. You can't do that either.Joe Carola
Thanks Joe.
Learn something everyday here at...Taunton University of Knowledge FHB Campus at Breaktime.
where ...
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I bid a job a few weeks back where the Architect specked a 18'span room using 2x12's which is fine until I saw that there was a 3-1/2" x 11-7/8" LVL Flush girder in there at mid-span with the bottom of the joist sheetrock for a finished basement.I called the Builder and told him to call the Architect because around here 2x12's measure anywhere from 11-1/2" to 11-5/16" and the LVL always measures 11-7/8". I told him that it's not a good idea to do that especially with a flush girder because the 2x12's will shrink and the LVL's wont shrink and there will be a problem right in the center of the floor and in the basement ceiling because the bottom of the 2x12's are already short by 3/8 - 1/2" already without any shrinkage. You would have to fur the whole ceiling down anyway because of this.I told him that the girder should be dropped or just use I-joists for a 18' span with no girder because it was just an open room above with no walls. No need for a girder. Archee's answer was to drop the girder and use 2x12's. Not a good answer in my opinion.
Joe Carola
I gotta say ... I'm using framing lumber for my rim joists on this job. The job is my own structure ... not for anyone else. But I'm building rims like headers using 2X10's with 2 1/2" blocking sandwiched between and 1/4" of ply screwed/glued along the top. This brings the size up to the 9 1/2" joists ... and these 'headers' sit on the 2X6 top plates running parrallel to the i-joists. Of course, I'm 'hoping' that 'shrinkage' doesn't manifest in future as a problem. On the two opposite walls I'm using lumber squash-blocks between the i-joists.
T.
""I gotta say ... I'm using framing lumber for my rim joists on this job. The job is my own structure ... not for anyone else.""So, what does that mean??? You will have a problem!Your not supposed to do that at all!! It's right there on an I-joists literature or websites. Your 2x's will shrink. Just because it's your house you can frame it the wrong way and have problems down the road?? Why don't you frame it the RIGHT way like your supposed to do???""But I'm building rims like headers using 2X10's with 2 1/2" blocking sandwiched between and 1/4" of ply screwed/glued along the top.""Why are you wasting your time an doing all of that? Just put a rimboard on for a box like your supposed to do or if you don't like the rimboard than use an LVL because they don't shrink and they are the same height as an I-joist.What are you using for a rimboard where you nail them into the I-joist?Joe Carola
To be honest I'm doing it primarily because of cost. The lumber yard wanted SO much more for the manufactured rim and, believe it or not, my architect, a long time builder himself, said to go ahead and us lumber. I even double checked with him after catching some flack from the board here and he okay'd it again.
I'm using lumber on the ends where I nail through as well. I do not see how it will cause a problem. The side rims ... parallell to the tji's ... are 16 OC away from the nearest i-joist and any shrinkage 'could' cause the floor along that edge to drop 1/16" or something, but I just don't see how basically building an outer box-frame to enclose the i-joists is going to negatively affect the joists. Infilled between the ends of the i-joists, on the top-plates, are MANY squash-blocks on end that are 1/16th higher than the joists and they will support the weight of the wall above up off of the joists EVEN IF the 2X's on edge experience some shrinkage.
I realize that some of the literature says "be sure to only use our manufactured product for rims" ... but there are always other ways to do things and I'm always suspicious of whomever says "only use our products..."
What do you believe the potential problems to be?
thanks -
T.
Edited 7/1/2006 10:44 pm ET by newbuilder
Thanks everyone ... lots of choices and that's what I came for. I'll have to deal with it one way or another this late afternoon. At this point I'm leaning towards shaving it down some, as I'm WAY overbuilt anyway with the size tji I'm using for the space ... I'm not worried about shaving 1/4" off of 10 feet of it ... perhaps apply the side-support per blue's suggestion. Thanks for the diagram, blue ... also a great fix Idea ... would have to plow through about 3 - 4 plywood sheets as they run vertically to the joists. But it's a great idea that I'm surprised didn't occur to me.
I think I'm going to lay that joist on it's side and use a circ-saw to shave off 1/4" Eeeeeeever so carefully. I'll drop a word or two here on how it all went.
Yeah ... very strange that this guy is humped. I've never seen that in my (limited) experience either. Never thought to me to check before taking them home.
thanks again,
T.
Edited 7/1/2006 6:14 pm ET by newbuilder
Maybe I'm overly optimistic, but 1/4" in the middle of a 13' span sounds like a situation that will flatten out something like 1/8" or so if decent subfloor is screwed down, unless the TJI in question is grossly overbuilt for the span.
Move that crowned joist to the side of the room where it won't be as noticable.
So... We're really talking about how to get 1/8" of hump out of a 13' span. Unless it's hardwood, that's not half bad, and better than 95% of the floors out there.
To get rid of 100% of that 1/8" I'd probably drop the joist hangers 1/8" and plane a shim so the top surface is flat. On the bottom side, a gradual 1/16" hump per foot is usually not noticeable in sheetrock, and better than most new construction, so some 1/16" sheetrock shims placed on either side of the low joist will essentially float out the low spot. If 1/2" rock was planned, I'd definitely up that to 5/8" since it goes up much flatter.
If there's harsh light, as from a tall or high window, shim it so there's no more than a gradual 1/32" per foot of hump or dip. That's about as good as it gets on the best sheetrock jobs.
Not that anyone out west ever straps anything, but I can see how it's also a good system for flattening out ceilings, while reducing sound transmision.
Good building
The TJI has a 1/4" crown to it...
The space below will be a finished ceiling...
You don't want to send it back for a replaceement...
I do not recommend modifying the flange in any way, shape or form.
What I would do is chisel out the mud sill or top plate, whatever the ends of the TJI will be bearing on, just a bit. I'd consider dropping it 1/8th inch, then the top flange of the crowned TJI will only sit 1/8" high. You could drop it the entire 1/4", just consider how that would affect sheetrocking the ceiling of the room below.
Prior to glueing and screwing the subfloor to the TJIs, put a level across the tops of the top flanges of the TJIs adjacent to the crowned one, spanning the one that you dropped the 1/8"-1/4". Tack shims in place to make up for the height differential so the subfloor will have good support.
Should take about 15-20 minutes.
Thanks, Mongo -
EXcellent!
T.
Hey there Mr. Newbuilder
Just a thought, would it be possible to just remove the defective joist from say the middle of the floor and use it closest the outside of the flooring layout. Just a thought for your schedule.
I believe that earlier in the thread someone or other mentioned that. And I am, indeed, going to do just that.
thanks for mentioning ..
T.