Is It Possible To Span A 2x12 19' Without The Floor Feeling Like A Trampoline? - Building & Construction - Page 3 - DIY Chatroom Home Improvement Forum
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Old 10-26-2017, 01:19 PM   #31
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


assuming that is a 50 gal tub and adding a 400lb point load at that location 3 2x12s is still fine. How you do your trusses is going to make a huge difference though. If you are going to have a load bearing wall on these floor joists to support the ceiling 3 2x12s isn't going to cut it. Assuming you go with a ridge board and 2x6s or 2x8s you're probably going to need a load bearing wall somewhere near the center for purlins. If you get engineered trusses then you won't need a load bearing wall anywhere on the 2nd floor and your 2x12s will be fine.


Yeah, I'll be using engineered trusses ( 24' span with 12/12 pitch) so you're right...none of the upstairs walls will be load bearing. Looks like 2x12's are the way to go. I'll be getting this plan approved by an engineer once when I get it coherent...but you've really helped out a lot man. Thanks for taking the time.
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Old 10-26-2017, 01:53 PM   #32
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


When we get thing approved by an engineer. They look at the plan as drawn and then draw a new set of plans with just the detail they would like to their standards. They will check all your numbers. You may not be happy with what they come back with.
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Old 10-26-2017, 02:32 PM   #33
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


Would you say engineers are overly cautious? I'm on the fence if I should just take it to the permitting office and seeing what they say. I mean ff they say its alight, the charts say its within limits, and actual framers on here say its good...thats probably good enough for me.
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Old 10-26-2017, 02:38 PM   #34
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


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Originally Posted by kimballfount View Post
Would you say engineers are overly cautious? I'm on the fence if I should just take it to the permitting office and seeing what they say. I mean ff they say its alight, the charts say its within limits, and actual framers on here say its good...thats probably good enough for me.
The engineer will give you nailing patterns, specs for blocking, specs for how to sheath between floors, any uplift connections/strapping if necessary, etc. If you want to use 2x12s they'll check the design for 2x12's. They'll probably also give you notes on how much you can drill/notch through them. My building department let me design and spec my own LVL ridge beam and load bearing headers with 0 words. Most requirements are in the IRC which is free online. For a full house your code department will probably want a stamp though. From my limited knowledge when you take it to an engineer he may even say 2 2x12s is okay but like others said for deflection purposes I would go with 3.
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Old 10-26-2017, 03:27 PM   #35
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


For joists that are SYP or Douglas Fir, in good condition, 11.25 inches tall, 1.5 inches wide, 12 inches on center, and 19 feet long between supports, the deflection calculated is 0.598 inches.

This translates to a deflection of L / 381.

A floor that bounces as you walk across it may just need to be stiffened with bridging, which spreads the load on each joist to adjoining joists, strengthening the whole floor.

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Old 10-26-2017, 05:37 PM   #36
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


There should never be more than 7 ft of span with out bridging.
Engineered bridging is always called for by engineers when are at the span limit.

Engineered bridging is ordered to fit what you need for joist height and what on center.
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Old 10-26-2017, 05:42 PM   #37
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


Could blocking be used as a substitute? I'm willing to bet I'll have a lot of left over 12" x 12" scraps left over after cutting the joists....seems like an easier endeavor as well

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Old 10-26-2017, 05:51 PM   #38
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


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Originally Posted by kimballfount View Post
Could blocking be used as a substitute? I'm willing to bet I'll have a lot of left over 12" x 12" scraps left over after cutting the joists....seems like an easier endeavor as well
No. Drywall will do the same as what you're describing. Cross bridging is more effective.

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Old 10-26-2017, 05:59 PM   #39
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Re: Is it possible to span a 2x12 19' without the floor feeling like a trampoline?


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Originally Posted by kimballfount View Post
Could blocking be used as a substitute? I'm willing to bet I'll have a lot of left over 12" x 12" scraps left over after cutting the joists....seems like an easier endeavor as well
When the floor sags we can imagine a space opening at the bottom between the block and the joist.
The bridging I posted, the engineers want it clues and nailed with 5 nails on each side.
So it would look like it has a better chance of success.
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