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Old 07-11-2009, 10:29 AM   #16
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what kind & size floor joists needed to span 15 feet?


Use 2x10's on 12" centers with 2 courses of solid blocking, which is superior to cross-bridging..... Use 5/8" T & G screwed and glued for best results. Don't forget to create a solid air barrier around the rimboard using DuPont Tyvek. That's what I'd do.

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Old 07-11-2009, 04:24 PM   #17
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what kind & size floor joists needed to span 15 feet?


To ress, my reason I stated cross- bridging is better than solid, for what it's worth:

Cross is stronger - it can be wedged into place making a tight connection between joists. This transmits the load more effectively. If there is a 1/16" gap between the block/joist, times 8 block bays= 1/2" of dead space not transmitting.

More importantly, as the article quoted brought out:

"Cross bridging is considered by far the best, as it allows the thrust to act parallel to the axis of the strut, and not across the grain (diagonally) as must be the case where single pieces of boards are used."

I may be nit-picking with engineering facts but now you know my reasoning. How will you be attaching the rims to the middle of the two story studs? Be safe, G
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Old 07-11-2009, 06:02 PM   #18
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what kind & size floor joists needed to span 15 feet?


Touche, Mr. Gbar. Your engineering results are very valid; but from my experience, i`ve had to pull the bridging to one side to make it flush to the bottom many times more than once, as the spacing in between joists is rarely uniform regardless of 16" or 12" centers. Unless the spacing in between joists is dead-nuts every time, bridging will not work as it should; meaning that you will have to 'modify' it to work in an odd spacing. The result will be a break in the system and will be as useless as tits on a bull. Blocking, when nailed in 3 spots (top, middle and bottom) and cut-to-fit at the time of installation will never have this problem, creating a solid member through the joisting that will be uninterrupted. I have used both methods over a thousand times each and would never opt to use bridging over blocking.

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