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Has anyone ever heard of this?

Mark Eatherton
Mark Eatherton Member Posts: 5,839
I received a call from a floor joist supplier today who said he had a system that was installed in August (staple up) and was commissioned in December of last year.

Recently, the upper floor of the dwelling realized a 1/2" drop in elevation due to the upper I joist of the I Joist system shrinking more than the lower I , thereby exerting a downward deflection on the flooring system.

I suppose that anything is possible, but in my many years of service, I have never run into this before.

Anyone else ever heard of it? If in fact it is true, we, the industry need to be aware of it.

Thanks all.

It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.


  • Gordy
    Gordy Member Posts: 9,514
    edited February 2014
    TJI or BCI

    I joist system? TJI is oriented strand board,, andBCI is ply wood.

    Are the flanges LVL, or wood? LVL is laminated wood! wood flange is dimensional lumber.

    Is he saying that the span deflected 1/2" in the center of the span? That's how I'm reading your post.

    I think there are a lot of variables to look into on such a claim.

    Span length?

    I Joist height?

    What's running with in the I Joist through knock outs as far as mechanicals plumbing etc. ( span loading).

    Moisture content of material on site ( material storage until used)

    Conditions in the basement ( humidity) if this is a floor over a basement.

    How was the staple up detail ? Tubing next to the top flange of I joist?

    Insulation detail of staple up?

    I really find this to be a stretch in a moisture stratification with in the I Joist itself. I find it hard to believe that moisture would be extracted that rapidly from just the upper portion of the I Joist wood likes to equalize.... It's Mother Nature you know.

    All in all I think there is product failure, and someone is looking else where for something to blame it on.

    I was never a big fan of the I Joist products just no meat, and potatoes to them. Around here the fire fighters all most refuse to go in an involved house if they know the floor is supported with I Joists.

    In the end to answer your question directly no never heard of it. Unless the floor was loaded with a flooring choice that the the joists could not carry. Stone etc.

    I think a moisture meter wood be the tool of choice. I would love to see the readings top flange to bottom flange.
  • hot_rod
    hot_rod Member Posts: 16,286
    i did see

    That heavy duty Advantech floor sheathing shrink about 1/2" in length and width when I cranked up a plate install for the sheetrockers one winter. They wanted it as warm as possible to tape and finish and the HVAC guys wisely did not want to run the furnaces, so I cranked the temperature to the underfloor.

    Those I-joists are typically stored outdoors and could take on moisture and swell, with enough heat I'd guess they would shrink down like the other manufactured wafer, chip, or ply type materials.

    Not sure where that 1/2'' dimension changed?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Bob Harper
    Bob Harper Member Posts: 914
    joist shrinkage?

    When you have engineered joists and still see shrinkage, its usually more the mudsills the rim joists are sitting on or interior columns on poor footings. If the floor is still level, then its probably not the mudsills. Engineered joists shrink very little in my experience and when they do, the similar components shrink uniformly. Did he measure the thickness of each plate? 
  • Gordy
    Gordy Member Posts: 9,514
    Staple up detail

    If it were insulated properly the moisture content if it were elevated would not be able to escape rapidly. The only place for it to go would be in the sub floor plywood, and insulation.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839

    Gordy, based on the fact that the letter of recommended actions is from the APA, I must assume it is a plywood chord, and not OSB. I will try and attach their recommendations to the end of this post. It is a PDF.

    As far as this alleged shrinkage is concerned, how many flat roofed 7-11's are there out there with black neoprene rubber roofs that are being exposed to even higher temperatures of operation without failure.

    I agree that it is probably another example of if you can't find another reason, and radiant flooring is installed, then it must be the radiant floors fault. But I always like to keep an open mind, and am hoping that it is an extremely isolated situation. I am going to reach out to the APA and ask them for any additional cases that they are aware of to see if it is a common place problem, or a fluke.

    Note that the information allegedly came from the RPA. I am also going to reach back to the former Technical Director and Executive directors to see if they remember anything in this regards. I don't think the APA would be so bold and brazen as to make up something like this, so I have to assume that they got their information from someone at the RPA.

    Will stand by for additional comments. Thanks to all who have contributed so far.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Gordy
    Gordy Member Posts: 9,514

    Sounds plausible in theory Mark....Or are they picking and choosing some RPA guidelines to their own defense?

    Obviously moisture content can be the culprit, but what is the standard acclimation period for their product? What percent moisture content is it shipped at, what operating steady state is it designed for, or most ideal?

    The depth of the IJoist plays into this also obviously the taller the more potential for moisture content stratification through out the depth of the I Joist.

    But then this can happen in a whole bunch of different scenarios.

    Some how there has to be a middle ground between wood product manufacturers, and radiant heating. Surely some type of standard can be agreed upon verses the. Blaming radiant heating every time something happens, and radiant happens to be in place.

    As you say how many roofs are framed with I joists, and what temperatures do they see through out its depth? But then no one looks at the roof for 1/2 inch deflection.
  • Ironman
    Ironman Member Posts: 6,868
    Missing Peices

    There are several missing peices to this puzzle. Particularly any info on the hydronic system. What's its maximum operating temp? How is the tubing installed? I have seen online hack advice that instructed for the tubing to be attached to the side of the Ijoist or even directly to the top flange. I've come across it in the field also.

    These "systems", of course, required elevated water temps in an attempt to compensate for the improper installation of the tubing. Ive never known of a properly designed and installed radiant system to damage a floor or framing members.

    If heat transfer plates were install and the floor surface temp limited to 82*, how could the Ijoist be damaged since it would be cooler or about the same as the floor surface?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Gordy
    Gordy Member Posts: 9,514
    edited February 2014
    I agree with Bob

    Apparently this is not an isolated problem the way the approach is taken from the letter. From your initial post this is what I thought to be an isolated case.

    What Bob is saying about the radiant heating details is what I was leading to in my first post.

    IF the APA truly is seeking help or advice then some details in the cases of radiant heating need be addressed. A poor install verse a quality one are two different animals.
  • icesailor
    icesailor Member Posts: 7,265

    I first must ask, what is the cellar girder made of? Laminated (built up) Dimensional lumber of some species of wood or are they some form of glued up laminated wood?

    On the second floor, do the I Joists run from plate to plate or is there some built up beam supporting the center span other than walls?

    Wood lumber will shrink or crush up to 1/4" in its 2" and 4", 6" etc. dimension. I've seen most 2X10-12" built up laminated beams shrink up to I" in their long dimension. Where the cellar girder is supported by a footing and lally column or pier, and doesn't move, and the mud sill joist shrinks along with all the lumber stacked up, the outside walls are one dimension and the outside walls are another. On the second floor, the middle of the house is lower than the edges. Any doors that are hinged at the outside wall and the knob is to the inside, will sooner or later, be hitting on the top. above the handle. I've seen places where I told the owner to put a screw jack under the two joists  spamming the wall that the door was on and push it up. Rather than cut a wedge off the top. It has the opposite wedge on the bottom. Fix the floor and the wedge goes away.

    Finally, on I-Joists, why do they call for "Crush Blocks" on the bearing ends of I-Joists if there isn't any shrinkage or crushing. There were very few jobs I ever saw them installed but they are shown in the installation instructions.

    I've seen every kind of shrinkage that can be seen. And in every case, someone was all in a sweat because their house was "Settling". No,  its shrinking. I'll bet I could find a few problem spots in the framing design.

    Another real problem spot is crossing beams, one supporting beam resting on another one. The shrinkage is multiplied for every beam.

    Someone is looking for someone else to blame for their bad design or bad application of framing principles.
  • Gordy
    Gordy Member Posts: 9,514

    I'm willing to bet that these are clear spans with no bearing walls or beams. This is typically one of the advantages to the I Joist system. Lighter materials spanning longer distances, with the ability to actually cut bigger holes for mechanicals in the middle 1/3 of the span verses the outter 1/4 in typical wood joists. Complete with knock outs for piping that seldom seek use because the framer is sloppy in lining joists up.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,688
    edited February 2014
    I take it....

    There's been no autopsy on the I joist? If I were guessing I would lean toward mechanical failure caused by:

    1. Improperly drilled holes

    2. Improper cross bridging or cross bridging removed.

    3. Improper engineering.

    If it were moisture related, I wouldn't blame the radiant unless it was leaking. It's pretty hard to get a clear idea of what happened during construction--not weather tight, things like that.

    Plus you mentioned it was installed in August. Humid climate?
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    I second

    What Gordy and HR said. I too cannot imagine that extreme a dimension with TGs unless the things were underwater maybe before installation...
  • Paul48
    Paul48 Member Posts: 4,469
    edited February 2014
    Really Slowwwww

    Maybe you could bring the temperature up slowly enough that the problem would not become apparent until the home warranty expires. Can we cut through the BS, and apply just a little common sense. I've driven a lot of 12 pennies into soaking wet lumber. So wet, you got a splat every time you drove the nail home.They drop the lumber load on the day they are suppose to. If the skies open up, fifteen minutes later, and no one covers the load....guess what.
  • Zman
    Zman Member Posts: 7,330

    I think that either the joists where exposed to extreme moisture (many days of rain uncovered and laying on the ground) or there is a source of moisture in the building.

    I have seen I joists bend even more than that only twice. Both were exposed to improperly humidity controlled hot tub and steam rooms. Both had compromised vapor barriers and the joists were exposed to near 100% humidity.

    I don't think for a second that joists that were dried at the factory and properly stored would deflect like that as a result of infloor heat.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Gordy
    Gordy Member Posts: 9,514
    edited February 2014
    From the oriented strand (TJI) people


    Not really what is going on with the APA issue, but does determine what moisture content is deemed serviceable.
  • Paul48
    Paul48 Member Posts: 4,469
    edited February 2014

    Only the upper floor in the dwelling? Maybe a clue in there. Was there any investigation into that specific case, or are they just searching for a credible accomplice?
  • Gordy
    Gordy Member Posts: 9,514
    Been thinking about this open mindedly

    When considering the letter to the RPA they are looking for help, and guidance. That's better than condemning radiant heat around their products.

    The how's, and whys this happend or is happening is leading to a high temp plate less radiant system that is attached to the upper flange of the joist possibly not insulated.

    In other words poor installation practices. If at the very least this is indeed a problem then maybe they could insert a section on radiant heating protocol in their instructions.

    Now IF this is indeed an effect of high temp poorly installed radiant heating then this should be a temporary effect. If drying of the upper say 1/4-1/3 of the I Joist is causing shrinkage due to moisture being driven out of the wood then after the heating season the total I Joist detail should acclimate itself through out its cross section. Woods a sponge always seeking equilibrium. So deflection should dissipate during the non heating season..

    I would personally like to see moisture meter reading through out the cross sectional area of the joist. Was this done? Or we're visual assumptions made we see radiant there is the source of the problem.

    I would also like to observe loading of the span, and attachments to, and with in the joist. I'm sure the APA observed these first before looking else where for a culprit.

    At the very least out of this I see an opportunity for the RPA getting a foot hold on proactive information rather than reactive information inserted into documentation for various wood product manufacturers. It always seems here that people come with problems after it's a done deal, and money is the only solution in righting a hacks wrongs. It gives radiant heating an undeserved black eye.

    We can not only depend on people with problems finding heating help.com.
    JUGHNE Member Posts: 9,756
    Just a crazy idea

    but are I joists a form of truss??  In the winter attic trusses have bottom cord upheaval due to being much warmer than the upper cord plus snow loading.  So if one thinks upside down and over heats the upper part of the I joist would we have the same reaction in reverse?
  • Paul48
    Paul48 Member Posts: 4,469
    Re: waiting for equilibrium

    If the bond between the members has been broken, it's a huge issue. Like taking a cutting torch to vertical member of a steel I-beam.
  • Gordy
    Gordy Member Posts: 9,514

    I don't believe it is that extreme of a case. That would call for removal of the joist.
  • icesailor
    icesailor Member Posts: 7,265
    Extreme blaming:

    I think that someone is looking for someone to share the blame for a mistake.

    There are far too many of these framing structures in existence and having no problems for this to have this problem and it not be common. Top and bottom chords are always finger jointed. The wood ends up being encapsulated with glue and resins. Its water impervious.

    I'll bet they are seeing this 1/2" deflection at the first joist running parallel to a gable end wall and there is no bridging from the rim joists/first truss to the first clear span. That clear span is supported on its ends, The Gable end truss is supported the whole length by the wall.

    Just because you can pull the trigger on a nail gun, doesn't mean you know what you are doing.
  • Gordy
    Gordy Member Posts: 9,514
    edited February 2014

    Ice they know what to look for as far as framing details not being followed. I would think that would be the first area to look for a problem. If those details meet their requirements then they will look at other possible sources of cause, and effect.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    Not sure Paul...

    In fact I am not sure of anything surrounding the alleged situation. I've offered to look into it further, but have not heard anything back. Based on the comments here at the Wall, I suspect it is a rare situation. I've also reached out to a couple of other major tubing extruders, and have not heard back from anyone yet.

    Thanks again to all for their input to date. I am working with the APA to re-write and better explain the conditions to avoid, including care and storage of their wood products prior to installation.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • ChicagoCooperator
    ChicagoCooperator Member Posts: 323
    edited February 2014
    Roof Truss Deflection

    I've heard of the massive roof truss deflection too.

    Did I miss what the span the 1/2" deflection was over?
  • Gordy
    Gordy Member Posts: 9,514
    edited February 2014
    I joist and floor truss

    Are two different types of framing members. The method of transferring the load top to bottom chord along its length is the same principle though.
  • Gordy
    Gordy Member Posts: 9,514
    edited February 2014
    Up heaving of bottom cord

    Would be due to the lateral bracing that transfers the load from top to bottom chord shrinking from temperatures in the attic being cold.

    In other words the width of the top chord shrinks along with the length of the lateral bracing. As you get to the middle of the bottom chord span the lateral bracing is longer so more shrinkage, the higher the roof pitch and longer the span the worse it gets. Couple all that with dry winter air sucking moisture out of the lumber.

    There is a different physics with what is POSSIBLY going on in the I joist situation.

    Mark is doing exactly what I think the APA is looking for, and that is guidlines to protect their products. Except Mark will do it in a more direct type of verbiage not an umbrella statement of bits, and pieces of information put together into what THEY think it should be.

    Hopefully his words do not get garbled in translation to a I JOIST guideline documentation.
  • Weezbo
    Weezbo Member Posts: 6,232
    Howdy Mark .

    A few things come to mind ,

    one is live weight vs dead load over span of engineered lumber .

    Another is the crush blocking and rim and box detail.

    another is ,is this an entirely "framed house and what kind of framing , if not say the differences between balloon framing , is it a log cabin ?

    moisture even in the form of rain on a flat deck while a big moisture problem , i think it would show in the decking even more than the tji or bci or whatever..

    there are two completely different dimensions to the cords and the bearing parts of tji and bci type , the speed ties do not even fit if there are two different types used on the same job...

    1/2 " displacement is different than 1/2" shrinkage .

    deflection and coefficients of elasticity are listed with each .


    there are a few ideas .

    *~//: )

    one thing that can happen too is framing with snow and ice on the deck could make some difference as well , shrinking though of the top coord is a first for me and our weather conditions are some of the most severe in the world.