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  1. #1
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    Default Another Floor Question....

    I have a question related to flooring. If this has been posted before, I'm sorry. I did a search, and did not find anything that quite addressed what I am wondering, at least not specific to my case. Here it goes.

    I just finished having an 1800 square foot home built. It was finished Sept. 19th of this year (2014). So it's only 3 months old. We moved in, and got settled. We put our entertainment center against one wall in the living room. The other side of this wall is the gym, which is built on slab. The rest of the house is over a conditioned crawlspace.

    My problem is that there is a lot of "percussion" to the floor. Standing almost anywhere in the living room, I can shift my weight from foot to foot, or just rise up on my toes repeatedly, and I can move the entertainment center. I can see the things on it rattle.

    Some build details: The joists are I-Joists. The webbing of the i joist is, I think, 3/8" thick OSB, and each i joist is 9 and 1/2" inches deep. The subfloor itself is 3/4" OSB, and the joists are spaced 16" on center. From what I have read, this is better than what it is required to be.

    I also can't really say there is much if any deflection in the floor. I've attached some pics to look at.

    I have read articles about sistering, shoring, etc... I'm just not sure why I would have this issue. I confess now, I am not skilled in carpentry or construction knowledge when compared to most of you. I'm looking for a starting point here. Also, there are spots that seem to do this more than others.

    The finished floor is duraceramic. An additional layer of subfloor was laid over the 3/4" OSB to take the dura ceramic tile. I don't know what it is or how thick.

    Is it possible I am transferring force through the tile? There does seem to be high and low spots in the floor.

    I'd like some direction please. Thank you.

    IMG_0313.JPGIMG_0314.JPGIMG_0315.JPGIMG_0316.JPGIMG_0318.JPG

    Last edited by Mitch Berry; 12-29-2014 at 11:58 AM.
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  2. #2
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    Default Re: Another Floor Question....

    "Some build details: The joists are I-Joists. The webbing of the i joist is, I think, 3/8" thick*OSB, and each i joist is 9 and 1/2" inches deep. The subfloor itself is 3/4"*OSB, and the joists are spaced 16" on center. From what I have read, this is better than what it is required to be.
    "

    A critical factor is missing: the span of the joists from bearing to bearing.

    If the joists are spanning to long of a distance, what you are describing could happen.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  3. #3
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    Default Re: Another Floor Question....

    One part missing is the span of the i-joists. The size and spacing of the i-joists are determined by the loads that are going to be imposed on them.
    You might ask the builder to provide you with a set of the stamped plans for the house,and see if it was built according to plan.


  4. #4
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    Default Re: Another Floor Question....

    Agree with JP. Sounds like an over-spanned joist problem. You'll likely have to get in a very knowledgeable contractor or better, a structural engineer to evaluate it. From here, we're just guessing.

    If you choose not to decide, you still have made a choice.

  5. #5
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    Default Re: Another Floor Question....

    A little off topic here, but from the pictures I would spend some time researching the requirements for a closed conditioned crawlspace!

    The beatings will continue until morale has improved. mgt.

  6. #6
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    Default Re: Another Floor Question....

    Quote Originally Posted by Vern Heiler View Post
    A little off topic here, but from the pictures I would spend some time researching the requirements for a closed conditioned crawlspace!
    Agreed, it looks like somebody was just shooting in the dark on how to do it.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  7. #7
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    Default Re: Another Floor Question....

    Quote Originally Posted by Scott Patterson View Post
    Agreed, it looks like somebody was just shooting in the dark on how to do it.

    What do you guys mean by that?



    Re: Jerry Peck on what you asked me: The i joists run north to south, and the span is about 30 feet. There are two support beams running east to west within that span. From one wall you have 9 feet, then a support beam, then 12 feet to another support beam, then the other wall.

    I had to break the first video into three parts because of the way my iphone would send them...

    https://www.youtube.com/watch?v=KMj_v8U28Ds
    https://www.youtube.com/watch?v=zFsRHrKtRnI
    https://www.youtube.com/watch?v=8K74bVIkS6U
    https://www.youtube.com/watch?v=j1S0HTk-IO0


  8. #8
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    Default Re: Another Floor Question....

    Like I said before. See if it was built according to plan.


  9. #9
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    Default Re: Another Floor Question....

    Quote Originally Posted by Mitch Berry View Post
    What do you guys mean by that?



    Re: Jerry Peck on what you asked me: The i joists run north to south, and the span is about 30 feet. There are two support beams running east to west within that span. From one wall you have 9 feet, then a support beam, then 12 feet to another support beam, then the other wall.

    I had to break the first video into three parts because of the way my iphone would send them...

    https://www.youtube.com/watch?v=KMj_v8U28Ds
    https://www.youtube.com/watch?v=zFsRHrKtRnI
    https://www.youtube.com/watch?v=8K74bVIkS6U
    https://www.youtube.com/watch?v=j1S0HTk-IO0
    Mitch, some of the things I noticed were: vapor barrier is not sealed to the columns and insulation on the foundation walls looks like it is fiber glass batt or not present at all. There are a lot of things that need to be done correctly that could not be seen in your pictures and with these discrepancies visible I would recommend further investigation.

    The beatings will continue until morale has improved. mgt.

  10. #10
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    Default Re: Another Floor Question....

    Quote Originally Posted by Vern Heiler View Post
    Mitch, some of the things I noticed were: vapor barrier is not sealed to the columns and insulation on the foundation walls looks like it is fiber glass batt or not present at all. There are a lot of things that need to be done correctly that could not be seen in your pictures and with these discrepancies visible I would recommend further investigation.

    I will do that. It does match the plans, and overall, I was more than impressed with my builder and his quality. This is the only issue I am having.

    As it stands now however, I was wondering if we could digress and go back to the initial topic of the post. With the opening post pictures and info, along with the videos, why would it be that I have the percussion issues I am having, do you suppose? I wouldn't think span is an issue either since there are two support beams inside of the 30' span (I.e., Wall, 9 ft, beam, 12 ft, beam, 9 ft, wall - as in the video). 9 or 12 feet should not be any problem whatsoever for 9.5 inch deep ijoists spaced 16" on center with a 3/4" subfloor.... from what I have read anyway. That's why I - with no real expertise of course - am wondering if this could have anything to do with the second layer of subfloor which was added to take the duraceramic tile, or the tile itself. If the flooring contractor had inconsistencies in his work, could I be transferring percussion through the tile or the second layer of subfloor?

    I don't know.

    I'll ask for the stamped plans in any case, and I have someone coming to look at it. I'm trying to get a consensus on some likely possibilities so I know how to proceed.

    Last edited by Mitch Berry; 12-29-2014 at 12:00 PM.

  11. #11
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    Default Re: Another Floor Question....

    Quote Originally Posted by Mitch Berry View Post
    I will do that, and I will ask for the stamped plans as well.

    As it stands now however, I was wondering if we could digress and go back to the initial topic of the post. With the opening post pictures and info, along with the videos, why would it be that I have the percussion issues I am having, do you suppose? I wouldn't think span is an issue either since there are two support beams inside of the 30' span (I.e., Wall, 9 ft, beam, 12 ft, beam, 9 ft, wall - as in the video). 9 or 12 feet should not be any problem whatsoever for 9.5 inch deep ijoists spaced 16" on center with a 3/4" subfloor.... from what I have read anyway. That's why I - with no real expertise of course - am wondering if this could have anything to do with the second layer of subfloor which was added to take the duraceramic tile, or the tile itself. If the flooring contractor had inconsistencies in his work, could I be transferring percussion through the tile or the second layer of subfloor?

    I don't know.


    I'll ask for the stamped plans in any case, and I have someone coming to look at it. I'm trying to get a consensus on some likely possibilities so I know how to proceed.
    If you wanted a floor with zero deflection you should have gone with the concrete filled crawlspace.

    The beatings will continue until morale has improved. mgt.

  12. #12
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    Default Re: Another Floor Question....

    Manufactured I-joists with OSB webs tend to be springy. That is their nature.

    You could have another beam installed in the middle of the 12' span.It could be supported by screws jacks on concrete piers. It would not be a structural member per se, just there to remove the deflection in the floor.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  13. #13
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    Default Re: Another Floor Question....

    There are several methods to stiffen the floor, but the floor structure looks pretty good from what I can see from your photos. ( I did not take the time to watch the videos)
    More intermediate bracing as mentioned earlier, bridging blocks, even adding a layer of plywood to the bottom of joist and securely glued and screwed in place are some methods.
    Check the plans, but it looks pretty substantial from here.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  14. #14
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    Default Re: Another Floor Question....

    The problem that is occurring has to do with the natural frequency of the floor. When the natural frequency is within a certain range floors tent to vibrate. We would need to know the span of the joists and the series of the I-joists. For a given depth manufacturers typically have several difference series with different flange dimensions.

    With I-joists there tended to be more problems when they were sized for a live load deflection of L/360. Many manufacturers recommend sizing for a live load deflection of L/480. Some manufacturers (like (Trus-Joist) have a sizing program that specifies joists based upon the percentage of people who find the floor acceptable regarding vibration. In other words, they would specify one I-joist that 50% of people would find acceptable, another that 75% of people would find acceptable, and another that 95% of people would find acceptable. the numbers are not the actual numbers from the program. They vary depending upon the joists selected.

    Another approach in designing floors is to calculate the natural frequency and then make sure it is not in the range where vibration tends to be a problem. It can be tricky since the joists selected and the span are a factor, but also the weight of the floor system. The heavier sub-flooring and tile will perform different than lighter sub-flooring and carpet.


  15. #15
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    Default Re: Another Floor Question....

    Quote Originally Posted by Jim Luttrall View Post
    There are several methods to stiffen the floor, but the floor structure looks pretty good from what I can see from your photos. ( I did not take the time to watch the videos)
    More intermediate bracing as mentioned earlier, bridging blocks, even adding a layer of plywood to the bottom of joist and securely glued and screwed in place are some methods.
    Check the plans, but it looks pretty substantial from here.
    I agree with Jim and everyone else.. Many homes require their floors to be stiffened with additional beams or supports to help take the flex out of the floor system. This is about your only option at this point.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  16. #16
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    Default Re: Another Floor Question....

    In my experience, this is not an uncommon problem with I-Joists. The installation is clearly within the manufacturer's specifications: They are not over-spanned, nor spaced too far apart, and the sub-floor is at least 3/4" thick. You might think that there is enough dead load applied to the sub-floor in the form of floor tiles, grout, and backing. You said that you could cause the movement at the entertainment center from anywhere in the living room. I suspect that you might also be able to cause it by standing in the kitchen and shifting your weight in the same way, because the joists are installed in a multiple-span condition and movement in the kitchen will be transferred to the living room. When I used to design floors with engineered lumber, I tried to avoid creating multiple-span conditions under adjoining rooms that were largely open and free of partition walls, like kitchens, living rooms, dining rooms, and great rooms. The weight of partition walls on the floor system works very well to dampen vibrations (think of a pressing your finger on a drum head.) But in situations were it could not be avoided, and in cases like yours, I always specified the installation of tension bridging to distribute the loads among the joists. Installing one row of tension bridging per span might help now, or installing another support beam under the living room like others have said would have the same effect.


  17. #17
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    Default Re: Another Floor Question....

    I think Mark's post touched on one of the critical issues when using I joists, which is what Series of I joists were used. Often times, around here, developers would use a particular Series of I joist where the load calcs ended up at the top end of that Series capabilities in order to save money instead of bumping up to the next Series. This produced a lot of bounce in floors. That was common 10-15 or so ago around here but is less frequent now. Developers in small residential have learned their lesson to some extent.
    However, with 9,12,9 spans Series shouldn't be an issue at all. Those are inconsequential spans for I joists. I would agree that the intermittent supports and related tension could be contributing factors.
    Another common defect issue is substrate installation. Was the plywood nailed or glued and screwed? Load rating and floor characteristics change depending on installation method.
    Probably not an issue but are the footers legit? If poorly done the footers may be bad.
    I would string a couple lines or use lasers in the crawl to see where the movement comes from. Using a sound meter might also help determine originating location.
    Beyond that the crawlspace could easily be acting as a echo chamber. That wouldn't affect movement but could make movement seem worse.
    With those types of spans I just don't see the I joists being the issue. I've frequently done I joists with 18', 20', 22' clean spans with no noticeable bounce. Then again I always upsize. Last thing you want is a client complaining.

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  18. #18
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    Default Re: Another Floor Question....

    Happens occasionally with I joists and stiffening will usually take care of the problem especially when the installation looks as good as yours (seen much worse).. I can say however I don't like the 2x4's nailed together and I would change those out to solid and treated, however I don't like using wood as girder supports.. also attach/secure the posts to the girders. Here is an easy explanation link of how to do the work.. an average experienced carpenter can do it but don't forget the adhesives.. Stiffening Engineered Floor Joists | All Floors | Flooring | This Old House
    In your home it appears by just stiffening the runs beneath the affected area and one more to each side should easily do the trick. And by the way I totally agree with the conditioned space reply, you could end up with moisture, mold and decay issues unless that suckers buttoned up well and every wood member is separated from the concrete with flashings or equivalent separation preventing potential rot.. just my two cents from my experience and does not infer professional advice, any death occurring from this advise is purely coincidental and not my fault! That's my disclaimer! OOPS! Almost forgot! Insulate those ducts!
    And thanks to Bridgeman for pointing out I need to both wear my glasses when I type and pay more attention!

    Last edited by kenny martin; 12-27-2014 at 04:51 PM.

  19. #19
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    Default Re: Another Floor Question....

    Listen everyone, I'd like to say thanks for taking the time to look at my photos, videos, and information and providing me with all your answers. I really didn't expect that much feedback, but I really appreciate it.

    A couple things I wanted to clear up; In the pics and videos, you guys are seeing a concrete wall with an interior wall/frame in front of it, and asking about insulation. That particular concrete stem wall is not an exterior stem wall. There is a room toward that direction which is built on slab, which is my home gym. That's why there is no insulation against those stem walls, since they are not exterior. The rest of the stem walls, as seen in the video, have insulation. I do agree however, that the lining on the floor should be sealed around the concrete blocks where the supports are, and I will take care to do that.

    About the floor, what I am getting from all your answers is this;

    The installation looks good, and is well within span tolerances based on all the info I provided. I'm still not sure if there is a physical difference in this case between deflection and vibration, or if those terms are being used interchangeably... but the solution to dampen the vibration appears to be adding two additional support beams, one each next to the existing ones under the living room. Totally doable.

    Kenny, when you say insulate the ducts, are you talking about all the spaces between the joists to dampen vibration? Maybe doing that, then adding the plywood , then the support beam would be the ticket to deaden the vibration.

    Thanks again guys...


  20. #20
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    Default Re: Another Floor Question....

    Insulating the ducts is just to ensure no potential for condensation/moisture if there is a temperature difference significant enough to create condensation on the metal ducts. As for insulating (or not) the wall with earth on the other side I would have to say you should still insulate just from experience being in crawlspaces doing work in the winter and seeing sweating on the blocks due to the exterior earth cold and the warmer crawlspace, even when it was not conditioned. Maybe my ass-umption was wrong in what I saw but that is once again just my"advice", bridgeman.. harhar.. good luck on your project. P.S. Deflection is just the reaction to loads (sagging or being pushed etc.,) vibration would also fall into the same category as it can cause members to move up and down) And that is just my opinion and not scientific by any means..

    Last edited by kenny martin; 12-27-2014 at 05:14 PM.

  21. #21
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    Default Re: Another Floor Question....

    Question.. what types of furniture etc. are in the room of what weight and where are they placed? Basically do you have heavy items like a piano or ? Also are there any walls placed over any of the I-joist spans but without added support beneath them? And lastly is it truss built or framed roof?


  22. #22
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    Default Re: Another Floor Question....

    Quote Originally Posted by kenny martin View Post
    Question.. what types of furniture etc. are in the room of what weight and where are they placed? Basically do you have heavy items like a piano or ? Also are there any walls placed over any of the I-joist spans but without added support beneath them? And lastly is it truss built or framed roof?

    Nothing heavy at all. Just the entertainment center in the videos and a couch and chair. I would say that all the walls have support under them.

    Truss built roof.


  23. #23
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    Default Re: Another Floor Question....

    ? Sorry, didn't see a video.. I'll check it out.

    - - - Updated - - -

    Last edited by kenny martin; 12-27-2014 at 08:15 PM.

  24. #24
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    Default Re: Another Floor Question....

    I just watched the video.. stiffening will likely do it.. seen it just like it before.. but before I convince myself fully, are there any cantilevered I-joists at all beneath the rooms adjacent to where it's happening?


  25. #25
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    Default Re: Another Floor Question....

    Quote Originally Posted by kenny martin View Post
    I just watched the video.. stiffening will likely do it.. seen it just like it before.. but before I convince myself fully, are there any cantilevered I-joists at all beneath the rooms adjacent to where it's happening?

    No. I will double check this thoroughly when I get back to the home, but I'm certain all of them are supported at both ends of their span, as are the beams which run perpendicular to them...

    I'm sure that's so, but I'll look again nevertheless.

    ...and by stiffening, you're on board with the running two additional support beams plan?


  26. #26
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    Default Re: Another Floor Question....

    Quote Originally Posted by Mitch Berry View Post
    Listen everyone, I'd like to say thanks for taking the time to look at my photos, videos, and information and providing me with all your answers. I really didn't expect that much feedback, but I really appreciate it.

    A couple things I wanted to clear up; In the pics and videos, you guys are seeing a concrete wall with an interior wall/frame in front of it, and asking about insulation. That particular concrete stem wall is not an exterior stem wall. There is a room toward that direction which is built on slab, which is my home gym. That's why there is no insulation against those stem walls, since they are not exterior. The rest of the stem walls, as seen in the video, have insulation. I do agree however, that the lining on the floor should be sealed around the concrete blocks where the supports are, and I will take care to do that.

    About the floor, what I am getting from all your answers is this;

    The installation looks good, and is well within span tolerances based on all the info I provided. I'm still not sure if there is a physical difference in this case between deflection and vibration, or if those terms are being used interchangeably... but the solution to dampen the vibration appears to be adding two additional support beams, one each next to the existing ones under the living room. Totally doable.

    Kenny, when you say insulate the ducts, are you talking about all the spaces between the joists to dampen vibration? Maybe doing that, then adding the plywood , then the support beam would be the ticket to deaden the vibration.

    Thanks again guys...
    Deflection and vibration are two different things. Deflection means the amount that the I-joist sag under a certain load (i.e. dead load/live load). Vibration is how much and at what frequency the floor system moves up and down when reacting to impact (i.e. walking, etc.).

    Sometimes just putting strapping on the bottom of the I-joists can make a big difference in vibration. This could be 2x4s or 2x6s nailed or screwed to the bottom of the I-joists. I would try either 3 rows at 1/4 of the span or 2 rows at 1/3 of the span apart. This is much cheaper than adding beams. Beams may need proper footings.


  27. #27
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    Default Re: Another Floor Question....

    Quote Originally Posted by kenny martin View Post
    Insulating the ducts is just to ensure no potential for condensation/moisture if there is a temperature difference significant enough to create condensation on the metal ducts. As for insulating (or not) the wall with earth on the other side I would have to say you should still insulate just from experience being in crawlspaces doing work in the winter and seeing sweating on the blocks due to the exterior earth cold and the warmer crawlspace, even when it was not conditioned. Maybe my ass-umption was wrong in what I saw but that is once again just my"advice", bridgeman.. harhar.. good luck on your project. P.S. Deflection is just the reaction to loads (sagging or being pushed etc.,) vibration would also fall into the same category as it can cause members to move up and down) And that is just my opinion and not scientific by any means..
    The new energy codes require the installation of a supply and return air duct into a sealed crawlspace system. Vented crawlspaces are not allowed. The walls and rim joists need to be insulated and the vapor barrier sealed. In the most recent house I built we ran a 2" thick slurry coat of concrete on the floor and spray foamed the walls and rims.

    The 9.5" I-Joist exceed the requirements for those spans. 7.5" would have been sufficient and there is no requirement by manufacturer that bridging be installed, though the most accepted method of "bridging" is a lateral strapping installed on the bottom.


  28. #28
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    Default Re: Another Floor Question....

    I have seen this vary concern in several new homes. You really only have a few options: contact the builder for review of the issue along with an engineer or contact the manufacturer of the I-joists for review. You need professional assistance and advice to determine if the floor system has been adequately installed.


  29. #29
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    Default Re: Another Floor Question....

    I have seen this in several homes I built using I-joists. As said before it is not usually a deflection problem but a vibration issue. Conventional framing is like a bass drum and the I-joist system is like a snare drum which created a completely different sensation when walking on the floor.


  30. #30
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    Default Re: Another Floor Question....

    I noticed a similar effect on a project that used Open Joists from UFP. A tall dresser in a wide bedroom has a handle that will sometimes rattle when walking across the floor.

    The practical solution is to fasten the piece of furniture to the wall to dampen it's movement, for example with a French Cleat.

    Otherwise it it bothers you, stiffening up the floor using one of the usual techniques should help.


  31. #31
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    Default Re: Another Floor Question....

    Could not tell very well from the videos however seeing that what bridging I saw was close to the support beams ?
    Like mentioned already these joists are springy in nature, I have had best results getting the bridging in the middle of the span, in this case between the two support beams, bridging if placed and installed correctly and optimally can significantly reduce the springiness in most cases I have experienced. With that additional sub-floor load, although may meet specs now, maybe better to have had 12 inch on center joists?
    Also have had different results from bridging materials, the more flimsier metal ones will tend to give somewhat and allow more deflection s than more heavier ones, but getting additional bridging more in the middle of the span(s) may help some?


  32. #32

    Default Re: Another Floor Question....

    Wandering slightly away from the original question but staying with I joists, I have had several firemen clients tell me they hate the things. Evidently, the problem is that the web burns much more rapidly than solid wood leading to floors that collapse. I have never seen (really never looked for) any documentation that supports this, only the fireman's comments.

    Anyone know of any official support for this belief.


  33. #33
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    Default Re: Another Floor Question....

    Quote Originally Posted by Marshall Brown View Post
    Wandering slightly away from the original question but staying with I joists, I have had several firemen clients tell me they hate the things. Evidently, the problem is that the web burns much more rapidly than solid wood leading to floors that collapse. I have never seen (really never looked for) any documentation that supports this, only the fireman's comments.

    Anyone know of any official support for this belief.
    It is a well know issue with I-joists and open web trusses. They burn faster and are more prone to collapse. In my area the township requires placards on commercial buildings identifying whether the structures have floor or roof trusses. They have also placed them on the signs at the entrances to residential developments.


  34. #34
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    Default Re: Another Floor Question....

    Quote Originally Posted by Mark Reinmiller View Post
    It is a well know issue with I-joists and open web trusses. They burn faster and are more prone to collapse. In my area the township requires placards on commercial buildings identifying whether the structures have floor or roof trusses. They have also placed them on the signs at the entrances to residential developments.
    Fire is a big issue with these, the bigger spans being created with these, and other engineered beams have less structure combined with faster burn rates and/or just due to the increased load on those spans floors collapsed much quicker.
    Friends house just recently caught fire, had I-Joists, started in the garages and then got in the attic which the fire department quickly got all put out, other than smoke and heat damage, water caused the I-joists to fail and collapse into the basement, not the fire, and not the whole house has to be demolished and rebuilt.

    Could have been bad if any fireman was inside when that happened.


  35. #35
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
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    26,250

    Default Re: Another Floor Question....

    Quote Originally Posted by Mark Reinmiller View Post
    In my area the township requires placards on commercial buildings identifying whether the structures have floor or roof trusses.
    Those signs are required throughout the entire state of Florida for other-than-residential buildings when wood roof framing and/or wood floor framing is installed. Other than one- and two-family and townhouses (to clarify).

    "R" = roofs
    "F" = floors
    "RF" = roof and floors

    Many fire marshals now require those signs. Florida requires them by statute as I recall.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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