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 size should they 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.). Thanks.

 

Try posting this question in framing & sub flooring. You are sure to get more responses. Good Luck

 

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.