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Old 02-14-2010, 04:54 PM   #1
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What are the code requirements for subfloor support?


I have a ranch style house that a 300 sq/ft loft was added on before I bought. The house had the celling and roof supported with 2x6 rafters 24in on center.

They decided that when they built the loft, they'd sister 1x2s on to the 2x6 rafters to make a 6.25 wide rafter to support the loft. They also doubled up on them to make them 12" on center. Because the loft is over hallways and bathrooms, they only span at most 5 feet.

One moron thing they did is that they made the sub floor out of particle board. No T&G, no plywood, just Rafter, particle board, carpet. Barf. Now there are pot holes everywhere.

So now I'm going to have to rip it up and put down 1" plywood. But I'm wondering, if I ever do an addition, and I want to span a 11' bedroom, Can you do that with 2x6 12" on center? Should I beef these up to 2x8s? Is that even enough to span an 11' section if it's 12" on center?

Seems like most new construction makes the sub floor 2x10s 16 on center for second stories...

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Old 02-14-2010, 05:26 PM   #2
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What are the code requirements for subfloor support?


if you ever do, use the 2x10s 12" o/c,,, exceeding code never comes back to bite you in the ***,,, 1" ply's heavy,,, i'd probably opt for t&g 3/4" ply.

then again, not a carpenter,,, i usually repair other conc guy's f/u's so what do i know ?

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Old 02-14-2010, 11:22 PM   #3
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What are the code requirements for subfloor support?


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Originally Posted by itsreallyconc View Post
if you ever do, use the 2x10s 12" o/c,,, exceeding code never comes back to bite you in the ***,,, 1" ply's heavy,,, i'd probably opt for t&g 3/4" ply.

then again, not a carpenter,,, i usually repair other conc guy's f/u's so what do i know ?
I don't think I can do 2x10s in my loft or my headroom will be too small and none of my molding will fit anymore.. Can I get by with 2x8s?
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Old 02-15-2010, 12:47 AM   #4
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What are the code requirements for subfloor support?


You cannot count the bathroom walls as bearing, unless they are supported with the floor joists below. Most locales have their own amendments to the IRC for particulars. A general floor span depends on the species and grade of wood used, an example: http://www.colonie.org/forms/building/bdspanab.pdf

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Old 02-15-2010, 09:10 AM   #5
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What are the code requirements for subfloor support?


Where are you located ?

2x6 12" OC as ceiling joists will span up to ~13' depending upon the grade of wood used
As floor joists they will span ~9' 9" L360 40/10 load

Span calculator:
http://www.awc.org/calculators/span/...rcalcstyle.asp

I never would use 2x6's for floor joists except maybe in a shed
I do have 2x6's as ceiling joists in my attic which are OK for the span
---no floor load on these
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Old 02-17-2010, 11:58 PM   #6
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What are the code requirements for subfloor support?


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Originally Posted by Scuba_Dave View Post
Where are you located ?

2x6 12" OC as ceiling joists will span up to ~13' depending upon the grade of wood used
As floor joists they will span ~9' 9" L360 40/10 load

Span calculator:
http://www.awc.org/calculators/span/...rcalcstyle.asp

I never would use 2x6's for floor joists except maybe in a shed
I do have 2x6's as ceiling joists in my attic which are OK for the span
---no floor load on these

I'd really like to use 2x10s but I'm thinking 2x8s are a good compromise for my situation. I'd sister up the existing 2x6s to 2x8s and then lay new quality 2x8s to span the other rooms if I ever do the addition..

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