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joist sizing

William521's Avatar
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05-22-04, 11:55 AM   #1  
joist sizing

Hello I have a simply question regarding the size of the joist in relation to there span. Lets say that the joists are all 16" o.c. and the span was 12 feet what sizes should the joists be ( 2 by 8, 2 by 10, etc). could you give a general explanation regarding this issue and include what sizes should be use in relation to how far they span (4 foot span, 6 foot span, 8 foot span etc.). example: 8 foot span requires a 2 by 8, 12 foor span requires a 2 by 10 etc.. Thanks abunch

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homerthefoamer's Avatar

Join Date: Feb 2004
Posts: 130

05-23-04, 07:02 PM   #2  
The answer would depend on what the floor 1s holding and what type of finish floor. A twelve foot span 16 o.c. a 2x8 would be fine. However if you intend on using ceramic tile I would go with a 2x10. I would check with your local building department they may have a minimum requirement. Hope this helps and good luck.

A_unique_name's Avatar

Join Date: Mar 2004
Posts: 175

05-24-04, 07:21 AM   #3  
I also put this in your other post

You don't say what these joists are being used for so I will give you some general information. The info below is based on Southern Yellow Pine #2 and may differ if you use a different species or grade.

If used only as ceiling joists (Only holding drywall with NO room above)
10 psf LL and 10 PSF DL

2 x 8
20'-1" @ 12" o/c
17'-5" @ 16" o/c
14'-2" @ 24" o/c

2 x 10
24'-0" @ 12" o/c
20'-9" @ 16" o/c
17'-0" @ 24" o/c

If used as Floor Joists
40 psf LL and 10 PSF DL

2 x 8
14'-2" @ 12" o/c
12'-10" @ 16" o/c
11'-0" @ 24" o/c

2 x 10
18'-0" @ 12" o/c
16'-1" @ 16" o/c
13'-2" @ 24" o/c

I hope that helps. IF you need more info please let me know what the specific use is for and the species of the material available in your area.
Good luck with your project.

William521's Avatar
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06-02-04, 10:36 AM   #4  
THANKS! Great help gyes. I have what I need to know.

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