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span length for reinforcing floor joists

Postby kyra » Sat Nov 17, 2007 7:24 pm

Hi everyone,

I am remodeling a recently bought home. One of the upstairs rooms is a game room and I plan on putting a pool table in it.

The original floor joists were 2x6 16" OC - I glued and nailed another joist on to existing joist - so now it is 4x6 14" OC. If I would add another joist in between, that would make the joist system 2x6 8" OC.

I want to know which one would be better to try.

How can I find out since there are no calculators I can find online that will allow me to get the appropriate spans as a function of sistered 4x6 joists or at a spacing of 8" OC?

The thing is the former owner added a second story, but did not reinforce the 2x6 ceiling (floor for the 2nd floor) joists. He simply laid 2x4's perpendicular to the "ceiling" joists 16" OC and used a single layer of tounge and grooved 3/4" floor boards. Upon inspection there are many places where the crossing 2x4 do not even tough the underlying joists.

The rest of information: Southern Pine grade #2; dead and live load of 10 and 40, respectively; deflection of L/360.

Maybe you could help me with an exact answer or tell me where should I look to calculate myself.

Thanks in advance!
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