2021 SDPWS - No Short Nails Allowed 1

[Deker]

For those who aren't yet aware, I recently learned that the 2021 SDPWS now explicitly requires that full length common nails be used for diaphragms and shear walls. Prior editions of the SDPWS required common nails but only listed a minimum fastener penetration, which many (including myself) interpreted to mean that short nails meeting the penetration requirement were permitted. In my experience, the use of short nails on shear walls and diaphragms is ubiquitous, so this represents a significant change to standard practice. Just thought I'd share.

 

[jerseyshore]

Thanks for the info.

From what I've seen, everyone uses standard 10d x 3" nails for framing & 8d x 2.5" nails for wall/floor sheathing. Sometimes 6d x 2 3/8" for sheathing. So that's what I design around and specify on my drawings.

 

[XR250]

Everyone around here uses skinny 10dx3" gun nails (box nail) - even when I specify commons

 

[jerseyshore]

The reality is that the framers use whatever the hell they want regardless of what we spec and 99% of the time it doesn't matter because it never sees full design loads.

 

[Aesur]

Not sure I follow the update here, is it not the same as it was? 8d common or 10d common sizes haven't changed and were always the specified nails, so in reality all they did was add the nail dimensions that match the previous nail dimensions/designations. I this update is just the committee following what connection suppliers, like Simpson, did by providing nail size/length because framers were just using whatever nail they wanted, regardless of what was spec'd, required or called out on the plans.

 

[Deker]

Aesur - Yes, common nails were always specified. However, the inclusion of "Minimum Fastener Penetration" in the tables led to the interpretation that a 10d short nail with 0.148" diameter was adequate as long as the penetration was met. Perhaps it's regional, but many firms in CA have notes in their drawings that explicitly permit short nails for sheathing applications. Even on jobs without explicit approval, I suspect most framers are using short nails for sheathing. It may be worth a conversation with the framers on your next wood job to verify.

In my opinion, the minimum fastener penetration / bearing length values should be eliminated from the tables if only a single nail length is permitted. Just list a range of sheathing thicknesses for which the nominal unit shears apply.

 

[Aesur]

Not sure I want to know what they are actually using on site. On our drawings we specifically call for 8d or 10d common and provide a table that shows the required dimensions. For Simpson connections we callout directly in the note the nail size. This is sim to calling out 16d common nails, which everyone complains about because of nail gun availability.

 

[RWW0002]

I can only guess at the intent of the code committee, but I agree with Aesur that this was likely a semantic change clarifying common nail sizes more so than a change in required penetration. I can see how it would be interpreted as such though (and may in fact require it - intentional or not)

I have used ICC-ES ESR 1539 quite a bit to evaluate different size nails due to nail guns. (

https://icc-es.org/report-listing/esr-1539/)

It contains similar tables to SDPWS but far a variety of nail sizes. It tabulates strength by diameter only and provides a "minimum fastener length" based on the minimum penetration. Based on this information it seems reasonable, as Deker suggests, to justify shorter nails.

Since framing nailers have taken over in the framing world, I no longer assume that framers will be using "common" diameter nails and now assume something closer to sinker diameter as a default. It seems like that dominates the gun nails I have spot checked in the past. The ICC report is very useful for checking the smaller diameter nails and things like clipped heads, etc. I think it could likely be used to justify shorter nails also, if necessary.

 

[CURVEB]

I wonder what effect this might have on blocking at panel joints? Aren't those typically constructed with a flat 2x? Might look a little odd to see the nails coming out the back side of those pieces if they have to be this long.

 

[Deker]

Didn't mean to imply that this was necessarily a new requirement as it appears this was always the intent, just pointing out that there is no longer any ambiguity that would lead one to permit short nails being used. I do wonder if this requirement has been fully thought out in terms of impact to certain diaphragm configurations, though. As CURVEB points out, you can walk under any roof and see quickly whether the framers are giving you full length 10d's or short nails by observing the 2x flat blocking at the panel edges. And the full length 10d's are going to lead to more splitting issues than experienced with short nails...perhaps using 3x flat blocking at all 10d locations is the solution.

Interestingly, I skimmed the oldest diaphragm and shear wall test reports I could find from APA and noticed that the tests used 10d duplex nails wherever possible to facilitate removal, so they weren't getting full penetration either. I also found this more recent research on using 10d shorts, but I haven't had a chance to read it yet: Link.

 

[RWW0002]

it appears this was always the intent, just pointing out that there is no longer any ambiguity that would lead one to permit short nails being used

Was this always the intent though? Why the minimum penetration requirements then? Based on the ICC report above, I think it might be reasonable to use shorter nails as long as minimum penetrations are used, but I agree that the new tables appear to indicate that the full length fasteners must be used.. I would have to dig back into that ICC report and see what kind of evidence they submitted for code equivalency in their data.