Nailing Plywood Diaphragms

[JedClampett]

I don't do wood structures that often, so my typical details are kind of rusty. I used to require hand driven nails (as opposed to nails from nail guns), because there was an structural advantage to using them. Does that still apply? I can't find any section in the code that indicates this.

 

[HeavyCivil]

I would compare the shank diameter of clipped head wire nails to that of common nails. No one is going to nail an entire roof diaphragm on by hand. If 8d or 10d nails that come in strips for framers are closer to the diameter of a 'box' nail, design for that.

No one I know does much hand-nailing of anything these days.

 

[river55]

Most people on the west coast specify a minimum diameter of nail that matches what they used in their calculation. Most calculations are based on common wire nails, so specify that diameter or common wire nails. How the contractor does the construction should be their decision, and I think many of the newer guns today are made to accept the larger diameter nails.

 

[MiketheEngineer]

The mfg's usually have "numbers" on their gunned nails. Work with those.

 

[msquared48]

Jed:

With the hand driven nails, you will not overdrive them.

However, if the nail guin is not set properly, overdriving can happen with nail guns, lowering the shear value of the panel.

You just have to inspect the nailing and set the gun to the proper power.

Mike McCann
MMC Engineering

 

[msquared48]

I know of no increase in the tablulated shear values for using hand driven nails, only a reduction for overdriving.

Mike McCann
MMC Engineering

 

[Cadair]

Technically, pneumatic nails are a proprietary product and are covered by an Evaluation Service Report and should be designed according to that. It is how they are "code compliant."

Here is one ESR report:

http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1539.pdf

Again, technically the diaphragm tables are based on nails that that conform to ASTM F1667, which has more than just diameter sizes. The capacity and ductility of diaphragms and shearwallls will also be based upon the length of the nail and its head.

So, it isn't just a matter of checking similar diameter size and penetration. It is either use their ESR or make sure the nails conform to ASTM F1667 and the sizes specified in the code/standard. That is where we stand currently at least. I don't like it and wish the pneumatic nail industry would standardize their nails.

 

[a2mfk]

The framers will usually adjust the pressure so there are few over-driven nails (first couple of the day maybe). And they will almost always usually supply just a few more nails than you specify...

 

[JedClampett]

Thank you for the information.
As usual, I'm impressed with how little I know. But I assume that if I define the plywood thickness (i.e. 19/32"), nail size (i.e. 10D), and the boundary, edge and field spacing, I have a pretty good chance of getting the right nails.
Another question; For the shear loads I calculate, It says that I need 3 inch nominal attachment pieces. I have no problems at the boundary walls and it even seems reasonable. But it's not clear, at least to me, whether I need to require 3 x wood trusses. It seems that the wood trusses I've seen have been made of 2 x 4's. If I need it, I need it, but I hate to require something that's weird and unusual.

 

[MiketheEngineer]

Are you using the correct table. Some are for roofs, some for walls. What code are you under??

If you need that much capacity - you might be screwed. But the 3'' is only required at the boundaries - that might help..

 

[JedClampett]

Using Table 2306.3.1. Load is about 480 plf and I need 19/32 inch panels anyhow to support the nailable insulation above the diaphragm.

 

[JRVinton]

If your load is from wind then you can increase the table values by 40% per section 2306.3.2. 10d's at 4" o.c. with 19/32" sheathing and 2x framing members is good for 425 plf * 1.4 = 595 plf and with a 4" nail spacing you don't need 3x framing at adjoining panel edges.