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Would anyone know of a website for joist,rafter span tables.Thanks
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I don't know of a website, but both the UBC and CABO code books have such tables.
*I've got one here... it may not apply to all areas, better check your local codes, but for what it's worth.... http://www.co.wake.nc.us/inspect/buildinginspections/buildinginspections.htmRoss
*Ross:Just curious: Do you live in wake county NC? I do.
*Matt, Nope, I live in Perth, Ontario... kind of a coincidence that I have a span table web page from where you live!Ross
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Try this:
< http://www.cwc.ca/english/wood_design/design_tools/SpanCalc0399/Span_US.htm>
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All, please give me your opinion:
In the house I am building the joist clear span in the master bedroom is 16' as specified by the structural engineer. The joists are 12" O.C. 2x10s. This seems like kind'a a long span to me.
The default lumber around these parts is SPF (Spruce-pine-fir).
Will this floor feel springy?
As an option I can go to SYP (Southern Yellow Pine) which is stronger (longer spans are allowed) but the framers don't like it as well as SYP tends to be less straight than SPF. The cost uplift for SYP is negligible.
What do you think?
*you mean you can buy a spruce 2x10. Down here in the deep south all our yards stock are spf 2x4's and possibly 2x6's. All we use is southern yellow pine for joists and work the kinks out LOL. Have you thought of using floor trusses. The open webs are great for running wiring, plumbing, ductwork, etc through and the wide (31/2") top cord provides plenty to nail the decking to. Even with syp i would use 2x12 joists 16" o.c in lieu of 2x10 @ 12"
*Doesn't seem out of the ordinary to me-12" OC makes a big difference. SYP is good, just choose your boards carefully, don't let them lay around the site too long-SYP goes crazy if left out in the sun too long. If this still bothers you, consider doubling every other joist, or going with Doug fir. Its more expensive, but strong and stable.-John
*I get a little wacky when left out in the sun too long too, but seriously, thanks for the tip. What should I cover em with? Clear polly would defenitely cook em, and black absorbs heat, so it would get pertty hot too... I don't think they sell doug fir around here in NC, but I knew someone would bring it up.As far as trusses, if your talking about actual trusses built of 2bys, I can't insulate between those - it's a crawl space, and much to the dismay of some of the folks here, the crawl will be ventilated. If you mean engineered wood I beams, they are too expensive.
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Regular hem-fir works fine for a bedroom load, 16' span, 2x10's @ 12" o.c., you don't need douglas fir or trusses. Check it on the span tables I gave a link for earlier in this thread.
You mentioned having an engineer - they overdesign, not under!
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By my calculation, using '94 UBC, Select Structural grade is needed for SPF at those criteria.
It wasn't deflection (springiness) but bending (breaking) that controls in this situation. You need a Fb of 1075, assuming LL of 40 PSF and DL of 15 PSF. Select structural allows 1250 according to my chart (23-I-A-1), No.1/No.2 is only 850.
You might want to check with your engineer! Size matters, but grade does also.
*Matt,My UBC Code Check book lists 2x10 at 12" centers to be good for 18'. 2x10 at 16" centers are listed as good for up to 16' 5". But that's for #2 doug fir.Structural Engineers tend to know what they're talking about when it comes to structure, so I'd believe him.Dan
*All:Thanks for your replies. At the time the structural engineer was doing his thing, I asked him what they design for, his reply was L360 min which is what is required by code. I told him OK, cool, but I don't want any springy floors.Gary:Our CABO code requires floors to be designed for 30PSF LL and 10 PSF DL for sleeping areas. 40+10 for living areas. I made a table showing E, Fb max-span values, but this fourm's software doesn't display tables worth a s**t.These CABO values are similar to the Wake Co. span charts referenced in 2nd reply to original post. (I live in Wake Co.) As gretel said, the designed 16' span 12" O.C is over designed for both 40 PSF and 50 PSF. I guess that answers my question.
*I don't agree with your engineer. He's probably correct in saying that the 2X10s are b strong enough, but they won't be very b stiff.Remember that strength and stiffness areb notthe same thing, and are only loosely related. I would suggest going to 2X12s at 16" O.C. It should be about the same price, with less pieces, and will be much stiffer due to the added depth. Ask your engineer if he's looked at the floor stiffness/vibration issue. He may not know that there's been a lot of research done on this lately. There are even formulas for predicting the vibration charachteristics of floor joists, floor trusses, and conventional floor joists.
*Matt,L360 has been pretty heavily questioned lately, again, not so much for total bending, but for springyness. Last article I read argued for closer to double that, especially for longer spans. At 16 feet L360 is .533 inches.Due to depth limitations, I once did an upstairs bedroom floor with a 14' span with 2x8's on 12" centers, #1 SPF. It was just within code, but it is springy.Steve
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For long spans l/360 will produce a floor considered springy by many people. Many Engineers use a max deflection of l/480 for these situations. This produces a floor 33% less springy.
*I'm not a PE but just spent a semester in strength of materials and was surprised to find how much deflection L/360 allows in long spans. It may meet code but could be unsettling to walk on. I've been in some buildings (residential and commercial) where it felt like you were walking across a trampoline. Seems as tho' more than few buildings, for cost reasons I imagine, are built to meet code and no more, even if the results are less than satisfactory.
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Would anyone know of a website for joist,rafter span tables.Thanks