Specifying lumber sheathing boards?

[abusementpark]

I have a project where the Architect wants to use 1x12 lumber sheathing boards as the roof decking over rafters spaced at 24 inches on ceneter. However, I am having trouble finding information on how to spec this and check its strength for all loading conditions. The sawn lumber section of NDS only appears to apply to members 2" nominal or greater.

Any help would be greatly appreciated.

 

[theonlynamenottaken]

In the footnotes for Table 4A, 4B in the NDS look at note #2. It addresses using sawn lumber 1", 1.25" and 1.50" thickness.

 

[woodman88]

Per the 2009/2012 IBC Section 2304.7, Table 2304.7(1) and Table 2304.7(2) the WWPA grades for the spaced roof sheathing is 3 common or standard. I have not found any design values for these grades. The AF&PA SDPWS-2008 gives the diaphragm values, but no live load capacities for the lumber that I can find.
The Timber Construction Manual 4th ed on pages 6-400 to 6-402 includes a table (Figure 6.11) that shows spans c-c in. to total uniform load (for 1x, deflection = l/240, MoE = 1800000psi, Fb = 1200psi) that shows 34" c-c will support 60psf. So 24"oc rafters is 34'oc at 45 degrees.
How the Timber Construction Manual values would compare with the 2009/2012 IBC lumber I could not say.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[abusementpark]

What's the difference between spaced sheathing and solid sheathing?

SDPWS doesn't give grading requirements.

 

[woodman88]

Sorry, I should of gave the solid sheathing info. Which is Utility and 4 common. The spaced sheathing is not for diaphragms but is used to space the boards apart for roof wood shingles, per IBC section 1507.8.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[focuseng]

In general, lumber 1x (in this case called "boards") are not structurally graded or assigned structural values unless they are graded as "decking" Using 1x12 "boards" will not get you structural values. I have never heard of 1x12 decking... There are values for diaphragm action in the SDPWS for decking. Again, Not sure 1x12 is applicable though...

I find it hard to believe you would have trouble with 1x boards spanning 24" o.c. in a roof application which may require a beam/span analysis. The diaphragm action is where you need to be attentive I would think.

______________
MAP

 

[abusementpark]

Can you get 1x12 board graded as decking?

What type of board is the SDPWS referring to? They gave nailing options of 1x6 and 1x8 members, but do not mention a material grade requirement. I figured I could try to use 1x12 members with a equivalent nailing frequency and get the same diaphragm values.