3/4" Wood Allowable Stress 2

[marinaman]

In looking thru the NDS, I do not see any data regarding the use of 3/4" thick wood boards (1x's)

I am looking at an existing building that has 1x6 wood used as the subfloor. The wood is southern yellow pine and spans 24". I'm trying to determine what the live load capacity for a 1x spanning 24" would be, but I can't find any data about allowable stresses for 1x material...much less 1x material loading in the weak direction.

Do you guys know where the allowables might be for something like this?

 

[SRCELL]

The NDS supplement has info for allowable stress of the species and section properties of the board size.

 

[marinaman]

SRCELL - The supplement does have data for species and sections....but not for 3/4" thick materials. That is my issue.

Unless, of course, I'm totally overlooking something?

 

[SRCELL]

Interesting. In the past I've used the values for 2"-4". Table 4E gives values for visually graded decking. Doing a spot check the Fb for decking is around twice what they give you for 2"-4".

 

[SlideRuleEra]

Wood's modulus of rupture increases as a member gets thinner (within reason). Since allowable stress is more or less proportional to modulus of rupture, 3/4" inch lumber (of the same species and grade) has higher allowable stress than 2" lumber. The change is not particularly dramatic (a factor of 1.11 for 3/4" compared to 2"). Since this factor is not mentioned in NDS, I just use the 2" value for thinner lumber.

From page 45 of "Wood Engineering" by Gurfinkel, 1973

 

[marinaman]

Thank you SlideRuleEra!! That's exactly what I needed!!