Out of plane web buckling of I-joists over interior supports

[BFeng]

I recently observed a 25 year old crawl space. The floor system was constructed of I-joists without designation markings spaced @ 19.2" o.c. Web blocking had not been installed at the time of construction at the ends or interior supports. Significant out of plane buckling has occurred since the floor system was constructed. Web blocking appears to have been added sinse the floor system was constructed but after some of the initial buckling had occured.I am recommending that the floor system be jacked and the I-joists be replaced or sistered with new members as the original members have essentially failed in my opinion. Does anyone have any other recommendations or approved solutions..

 

[msquared48]

From looking at the picture, with the discoloration, it looks like there may be moisture issues here too weakening the joist, possibly being the ultimate cause of the buckling.

Is this the case or am I seeing things?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[JAE]

I would guess that the I-joists (plywood web joists) were possibly overloaded, exceeding the bearing reaction limits where bearing stiffners would be needed.

Jacking the I-joists up to relieve the existing loading would be a good step. You could potentially glue and screw plywood webs over the "flange" ends and extend the new webs back 2 to 3 feet. Adding blocking at this stage, after the damage to the webs, may not be a competent solution.

 

[ToadJones]

I like JAE's idea about essentially making a box beam at the ends and over supports.

The problem with jacking, is, where to jack it? You can't really place a jacking system under the buckled/crippled joists.
With that amount of buckling, I would assume there is some noticeable damage to the finishes above (if it is finished).

I am assuming that the photo is showing an area over an interior support. You can see the deflection in the bottom flange. Is there a load bearing wall directly above the steel beam? The area looks to be heavily loaded.

I know from the I-joists I have installed that the ends came standard with blocking which had limits as to how much you could cut which sucked because sometimes it forces you to cut both ends in order not to exceed the limits. But, I have never seen an i-joist installed with no blocking at the ends. There is usually a load bearing wall directly above. We usually installed blocking/bridging over the interior supports to help transfer load down to the main supports. Surprised that wasn't down here.

 

[BAretired]

It would be difficult to replace or sister the joists without removing the entire floor, but that may be the only acceptable option.

BA

 

[BFeng]

Thank you for your contributions. I do believe and failed to mention earlier that moisture has been a problem in the past and another contributing factor in wanting to replace or siter new members. It really is quite a mess. I was going to recommend sistering 12" or 14" deep open web flat trusses beside the 16" deep existing I-Joists. Jacking the new trusses and then installing the support bearing under the trusses. I would coordinate jack locations with the truss manufacturer. Any other suggestions would be greatly appreciated.

 

[MikeHalloran]

A carpenter of my acquaintance built a small cabin, then built a shed next to it to house his boat, and a marine railway with hinged distal end to keep it out of the ice, all from wood, including the wheels that carried the boat. He didn't have power for his circular saw until it was all nearly done; most of the work was done with a crosscut saw. Of course that was fifty years ago, I haven't met a carpenter like Rudy since, and I suspect he may be unavailable now.

The problem is that you have to jack the floor, and the logical way to do that is by jacking the upper flange of the i-joist against the lower flange. Of each. On both sides of the web.

I'm >imagining< that Rudy would do it with a pair of plywood wedges, on either side of each web. Rudy would face the edges of the plywood with veneer so they'd slide easily. He'd probably restore the planarity of the web by squeezing the wedges and the web with those big carpenter's clamps that look like machinist's clamps made from wood, or maybe with through bolts and fender washers. Rudy would probably build a hardwood snail cam into the plywood so he could force the flanges apart and straight without hammering on anything; he was _that_ kind of carpenter.

I don't know what the hell _I_ would do.



Mike Halloran
Pembroke Pines, FL, USA

 

[ToadJones]

Sounds like Norm Abram!

 

[dcarr82775]

Planarity.....damn those mechanical guys use fancy words

 

[MikeHalloran]

Rudy was one of those guys who could start, drive and set a framing nail in three blows, and only used a circular saw when he was _not_ in a hurry.



Mike Halloran
Pembroke Pines, FL, USA

 

[ToadJones]

Mike-
I used a 20 oz. hammer in my nail-bending days.
On a good day, I could set, and drive a "spike" in three blows....usually only in SPF lumber. Good ole' southern yellow pine or LVLs and we're talking 5 blows.

 

[ToadJones]

reminds me of the movie Rudy....that kid was a real hard ass

 

[RFreund]

Our family owns a small general contracting business now over a 100 yrs old, who does the framing themselves and most of the carpentry. This Rudy reminds me of the stories I would hear about my great grandpa and the way they used to do things... Sharpen the hand saw at lunch, no crane to set trusses and I was always taught the proper way to nail was "set, spike!" Must have been for nailing sheathing with "8's" cause I could never get 2 blows for spikes!

 

[ToadJones]

I only ever hear "SET, SPIKE" when we were roofing. It is virtually required for roofing by hand nailing....which no one does any more.
I can remember the first guy i ever worked for was a roofer and he used to yell "SET, SPIKE" all the time trying to urge us young greenhorns on.

 

[a2mfk]

Without knowing what is bearing at that exact location, despite the ugliness I wouldn't be that concerned. Are you jacking because there is a dip in the floor and interior distress?

As it was pointed out, looks like moisture is an issue, which takes away the tiny bit of vertical load resistance that plywood web had, as it wasn't blocked originally, so it buckled. But what is that web doing at that location anyway once you install some additional 2x4 or 4x4 blocking to each side(maybe PT because of the moisture)? You don't have moment to worry about over the support...

A small chunk of 2x4 x 2' tall still has an incredible axial load capacity. If you still want to reinforce the web and joist you could attach new plywood to the outside face of the joist by nailing or screwing into the top/bottom webs, I use an oversized piece of 3/4" for this.

HTH,
Andrew