Blocking or x bracing to tighten up TJI floor?
BrunoF
| Posted in General Questions on
The framers are almost finished with my barn build and I may want to have them install blocking or x bracing between my loft joists to get rid of some of the bounce bit I’m not sure which one is more effective.
This is a barn so I am essentially at max span for L/360 ratings. Specifically, I have 16” deep TJI360s spaced at 19.2”, spanning 25’1” with 3/4 subfloor glued above.
any thoughts on the best way to tighten up that floor? Thx!
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https://www.techsupport.weyerhaeuser.com/hc/en-us/articles/204957590-Does-a-TJI-Floor-System-Require-Mid-Span-Bridging
If I was to try anything it would be tension x bracing, something like the Simpson x brace, but I doubt you will see a ton of improvement.
At 25' unfortunately l/360 will be bouncy no matter what you do. Blocking won't do much and the x bracing needs to go in before the subfloor.
If there are interior walls, you can solidly connect those to the roof and the floor essentially building a giant truss. That will significantly reduce the bounce.
Other option is to laminate (glue and nail) a full length 2x6 to the bottom flange. This will effectively increase the I joist one size up which will make a big difference.
Not sure what your layout is like, the space requirements underneath are, but consider adding a beam underneath the joists to half the span.
Jamie
How tall is the ceiling?
Perhaps diagonal braces to both walls would effectively shorten the span
The ceiling is around 11’ above the slab and the space below needs to be fully open so no room for beams. I might be able to do 1x strapping on the bottom of the joists if that would help.
No offense, but you are really running out of options. I can think of no solution that is cheaper than a dozen more TJI's would have been during construction
You need absolute clear span for every foot of space? No shelving lockers benches along the walls?
You need absolute clear span downstairs and upstairs?
Sometimes one must give something to get something
If you must span 25 feet with the limited depth of 16 inches and can’t tolerate much deflection my guess is steel or concrete are your only options.
Were the plans reviewed by a structural engineer? Was deflection discussed with the engineer?
My guess is this is being built without any engineers input or maybe just enough to get the plans approved.
If by chance an engineer did put his stamp on your plan at least get his advice before adding stuff to his plan.
Walta
No. This is a barn, exempt from permits, engineers and inspections. There is nothing in the loft except subfloor, so there was no need to go any further than span charts for the TJIs. The structure is sound, I am just trying to get some bounce out if I can.
BrunoF,
Perhaps you could glue and screw 1/2 to 3/4 plywood to the bottoms of all the TJIs and create a psuedo SIP like panel. I will rely on the more qualified posters to pass judgement on the effectiveness of this idea. In any case, be sure you are 100% done with any wiring or mechanicals before doing the skin idea and don't plan on putting hoists on the ceiling.
Alternatively, there are ways to add side pieces to the webs of the TJIs. There are some very specific details that must be observed when doing so, so again I will let others with real-time experience weigh in on the effectiveness of doing this. It would be a bit more labor intensive, too.
jberks is right about getting a beam in place if you intend to use the loft for significant storage. I suspect that a beam 6-8' off the back or front wall would be effective in shortening the span's behavior toward a stiffer floor. The beam could allow for a hoist if you are working on vehicles.
Try this article:
https://www.finehomebuilding.com/2004/11/01/correcting-a-bouncy-i-joist-floor
BrunoF,
If it's just the bounciness you don't like, perhaps counter-intuitively, loading the floor will significantly reduce it. That comes at the price of some deflection, but in a workshop that probably doesn't matter much.
Seems to me every joint in the X brace has so much flex that it makes the idea much less effective.
If you are going to add X bracing consider pulling up a row of plywood and weaving a continuous steel strip as the X bracing. Putting the strip under tendon before fastening the center would be even better. Thinking of steel banding like used for shipping.
Walta