# Flex in bending for nominal lumber? Need help.



## jpranch (Dec 13, 2016)

Would anybody have the Fb  values for #1 Douglas Fir, kiln dried that is 16” & 18” tall x 1 1/2” thick nominal??? Normal duration.


----------



## jpranch (Dec 13, 2016)

I would expect that number to be over 2,000?


----------



## fatboy (Dec 13, 2016)

Looks like 1300-1350, for #1, depends on South or Larch.

https://www.google.com/url?sa=t&rct...QffpFjLow&sig2=LUc71MUo8IRYUGE3XQgH3Q&cad=rja


----------



## Phil (Dec 13, 2016)

fatboy - that table is for beams and stringers. Here are some definitions
Dimensional Lumber:  2"-4" nominal thickness and 2" or more in width
Beams and Stringers: 5" or greater nominal thickness and width more than 2" greater than thickness
Posts and Timbers: square of approximately square, 5x5 nominal or larger and width not more than 2" greater than thickness.

1-1/2 x 16 or 18 is an odd size (1-1/4 thick)., I think it would be classified as a board but still use the dimensional lumber design values. I recommend calling the WWPA to confirm. The reference design values are in the NDS Supplement, http://www.awc.org/pdf/codes-standards/publications/nds/AWC-NDS2015-Supplement-ViewOnly-1411.pdf .

DF dimensional lumber is on page 35 (pdf page 42). See Table 4a footnote 2 about boards. If it used as a joist of rafter (closely spaced repetitive member) the reference design value can be multiplied by 1.15. If it is used flat (like a deck board) the reference design value can be multiplied by 1.2. For more information on adjustment factors, see section 4.3 of the NDS http://www.awc.org/pdf/codes-standards/publications/nds/AWC-NDS2015-ViewOnly-1603.pdf


----------



## fatboy (Dec 14, 2016)

I was giving him a starting point.............. I saw the heading on the table, and know what it meant.


----------



## steveray (Dec 14, 2016)

If you were a customer, I would tell you the answer is "hire an engineer"....Because I don't have time to find that answer..But I might be able to run it through beamcheck if you can give me all of the info...


----------



## jpranch (Dec 15, 2016)

Steveray, and fatboy, that is what I ended up doing. Got a structural engineer review and stamp the plan. Turns out that it was timber framed. The framing plan wasn't much to say the least until the engineer got involved. Thanks.


----------



## steveray (Dec 16, 2016)

jpranch said:


> Steveray, and fatboy, that is what I ended up doing. Got a structural engineer review and stamp the plan. Turns out that it was timber framed. The framing plan wasn't much to say the least until the engineer got involved. Thanks.


I see that a bit...Seems like everyone is just supposed to accept that the timber framers know what they are doing....I tell them it will be a lot faster and easier with an engineer or give me lumber sizes and a way to verify them...


----------

