Wall Stud and Floor Joist Spacing
Hello Everyone – hopefully a quick, simple question.
I’m building a 24’x32′ workshop and trying to create the framing layout using advanced framing principles. Trusses will be 24″ OC and aligned with the 2×6 wall studs directly below and sitting on a single top plate. All that makes sense.
I plan on using 2x10s for the floor joists, spaced 16″ OC. A 2×10 will also be used for the rim joist around the perimeter. Subfloor is 3/4″ OSB T&G.
After stepping back and looking at it, it’s obvious that the wall studs (24″ OC) don’t align with the floor joists (16″ OC). If I set the joists at 24″ OC, I would need to step up to some type of I-joist. (I’m spanning a 14′ length and a 10′ length below.) I haven’t gotten an actual quote yet but anytime in the past when I’ve compared I-joist to solid lumber, it was significantly cheaper to use the solid material.
Will the solid 2×10 rim joist allow me to use 16″ spacing on the floor joists? Seems like it provides a direct load path from the wall studs to the foundation.
Thanks for the help.
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Replies
2x10 can span 14' @ 24" centers depending on the conditions. Variables include wood type (can you get D. fir?), lumber grade, sub-floor thickness, sub-floor glue, including bridging or strapping.
You say "span 14' with 10' below", what do you mean by 10' below?
Easy alternatives are upping to a 2x12, or I-joists.
Sorry I wasn't more clear plumb_bob. Let me elaborate a little.
The total building is 24' wide. The floor joists will attach to a girder beam but the beam is not centered with respect to the building. Instead of all floor joists being 12' long, the joists on one side of the beam are 14' long and the joists on the other side of the beam are 10' long.
I live in the in the southeast, so southern yellow pine is what's readily available. I'm ok with that because pine is a good, strong wood.
Using the span charts from the southern pine website, a 2x10 @ 16" OC will span 14' with a 40 psf live load, 10 psf dead load and deflection of L/360. When the joists are set on 24" centers, they will only span 11'6" for the same load - hence my problem.
Fortunately, since the rim joist is a full 2x10, it will distribute the load from above (walls and trusses at 24" centers) to the floor joists below (at 16" centers) - according to the other replies to this thread. I believe I'm OK with this set-up.
Appreciate the help from everyone.
Southern Yellow Pine (SYP) is typically the strongest avaialable wood speecies for framing. I spec SYP anywhere I need something a little beefier than usual. You can also special order MSR (Machine Stress Rated) lumber, which is graded by a machine instead of visually, so you really do know what you're getting. MSR lumber is always SYP from what I've seen, and you get a pristine board that way, stronger than even a #1 visually graded board would be. It does cost more though.
Bill
Bill,
I use to believe SYP was superior, but with the 2013 design value change SYP and SPF are essentially equivalent, design wise. All I find now is that SYP is harder to pack around, has a higher tendency to warp, and is harder on the saw. At least for what we have in the south! Compare the values between SYP in the first doc and the SPF values in the 2nd.
https://www.southernpine.com/app/uploads/TABLE01_L1.pdf
https://awc.org/wp-content/uploads/2022/01/AWC-SpanTables2012-DVJRAddendum-1403.pdf
Unless there is something unusual on your project, assuming you're talking about the first floor framing, a 2x rim allows you to mix-and-match framing member spacing--so you should be fine.
Bluegoose68,
Everything you are doing is fine. Remember to add blocking under any built up posts.