New house Louisana Pacific I beams too far apart

This house is about 2 years old now. Two story house on a unfinished basement. There is a lot of noise from the walls and subfloor (creaks and pops) when walking on it. I carefully screwed down the subfloor to the LP wooden I-beams, but this makes no difference since the 3/4 OSB that makes up the subfloor is sitting across I-beams that are 24" OC apart. I can visibly see the OSB flexing when stepping in gap b/w the I-beams. The OSB is 4x8' sheet tounge and groove on the 8' side. The span of the unsupported beam is about 19' with the longest beam being 29'.
24" seems a bit much to prevent minor floor noise. I am wondering what can be done to make the floor as quiet as possible. My solution up until now is to take up the OSB and install "struts" between the I- beams, but I am not sure how the strut should be constructed and how far apart they should be. Thanks for your suggestions!
Chris
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24" is fairly common with I beams and engineered floor joists. Are you sure the sub is 3/4? The simplest thing to do would be to run another layer of 15/32 osb on top of the existing sub floor. Run it 90 deg to the existing. Glue and screw.

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There would be more joists under each sheet if the sheets were run in the same direction as the existing subfloor. If they're run in the same direction there's also more leeway in offsetting the sheets so the joints won't line up.
To the OP: If the main objection is for the first floor, you could stiffen up the floor more by adding additional blocking between the joists or by adding pywood/OSB to the exposed undersides of the first floor joists.
R
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Osb tends to flex more in one direction. Going 90 deg gives you more rigidity in both directions. Blocking is not going to lower the flex as much as a more rigid floor surface would. The more rigid surface will transfer the load farther out. And this also involves the least tear down.
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Glue is important. Also good quality plywood. Blocking and or manufactured struts are good too. 24" is standard. You can look at the manufactured truss and see if it is sized for the span.
So, I would take up the floor since it is screwed......(literally) and figuratively, and block or strut as per manufacturer suggestion. Use a good quality 3/4" 5 ply t and g. I use 2 - 4 - 1 or 1 1/8" t and g ply. It is really the best. Gluing is important, and do not be light with the glue.....It acts as a bed and helps with squeek. Good luck...... If you put more ply down on top of osb you still have "buried the squeek" and added weight to the joist.
jloomis

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On Dec 30, 7:23am, snipped-for-privacy@gmail.com wrote:

Chris-
I-joists at 24" o/c is allowable but imo, a little on the optomistic side. :(
How deep are you I-joists? you mention an average span of 19' and longest span of 29'?
Wooden floors can be quite noisy, esp when over an unfinished basement. You mention visible movement but can you associate the visible movement with noise?
Before you go through the work & expense of............
adding blocking or another layer of sheathing or removing and replacing sheathing with thicker T&G plywood
be sure you really have determined the source(s) of the noise......otherwise all the work will be wasted.
LP has blocking designs, you can use rim board or I-joists. They both need to be cut to fit. I would suggest not using sawn lumber, use "engineered" lumber.
Blocking could be added from below w/o having to R&R the current sheathing but it would rather tediuous.
cheers Bob
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On Dec 30, 10:23am, snipped-for-privacy@gmail.com wrote:

Most of the info posted in reply is good as far as it goes. However, since you note "a lot of noise from the walls and subfloor ...", Iwould, if it were my house, invest in a forensic engineer or architect to investigate the entire frame. This on the theory that 'nose' suggests movement and movement suggest structural problems. T
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snipped-for-privacy@bellsouth.net wrote:

Not at all. ALL structures move (deflect) under load. Deflection limits are one of the design criterion and typical residential floors are designed for deflection up to L/360 at maximum allowable load. So, for the 19' span listed above, a deflection of up to 5/8" is acceptable for most building codes. Movement does not at all correlate to a structural problem. It may be an annoyance, but that is far different from being a structural problem.
Often the issue isn't the deflection itself, but the damping of the floor structure. A heavier floor often "feels" much better even if it has the same or even greater deflection as compared to a lighter floor. The reason is that the dynamics from someone walking across the floor can be quite different.
Matt
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Chris-
Matt's comment

from being a structural problem. "<<<<
is right on the money.
Noise / deflection / springiness is annoying but usually nothign more. :(
Depending on how serious you are about eliminating (reducing) the noise, I would suggest getting an engineer experienced in floor diaphragm dynamics out to take a listen.
cheers Bob
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