How to Safely Select Nail Substitutions for Connectors

A few days ago, I was speaking to a customer about an application using nail substitutions for a joist hanger installation. Her questions come up often, so I thought I would dedicate a blog post to some of the resources available that cover the use of different nails in connectors.

Designers and builders often wish to use different fasteners than the catalog specifies. The application could require short nails that don’t penetrate through the back of a ledger or they want to use screws or sinker nails for easier installation. The Wood Connectors Catalog provides multiple options for alternate nailing for face mount hangers and straight straps on page 27.

Fastener Reduction Factors
Fastener Reduction Factors

The load adjustments for alternate fasteners cover substitutions from a common diameter of 16d to a 10d, or a 10d to an 8d. Multiple different replacement lengths are also covered, with reduction factors ranging from 0.64 to 1.0.

It is important to remember that double shear hangers require 3” minimum joist nails. Short nails installed at an angle in double shear hangers will not have adequate penetration into the header.

Fastener - Double Shear
Fastener – Double Shear

Pneumatic nail guns used for connector installation are commonly referred to as positive placement nail guns. These tools either have a nose piece that locates connector hole, or the nail itself protrudes from the tool so that the installer can line the nail up with the hole. Most positive placement tools do not accept nails longer than 2½”, so framers using these tools will want to use 1½” or 2½” nails. To accommodate installers using pneumatic nails, we have a technical bulletin T-PNUEMATIC. This bulletin provides adjustment factors for many of our most common embedded holdowns, post caps and bases, hangers and twist straps.

The question of nail size also comes up when attaching hangers to rim board, which can range from 1” to 1¾”. The adjustment factors in C-2013 don’t necessarily apply with rim board, since the material may be thinner the length of the nails used. We also have a technical bulletin for that application – T-RIMBDHGR.

Rim Board Reduction Factors
Rim Board Reduction Factors

Several of the reduction factors are the same as those in the catalog. Testing of hangers with 10dx1½ nails on 1” OSB or 1¼” LVL did not do as well, however. We observed that once the nails withdrew a little bit under load, they quickly lost capacity. For that reason, we recommend full length 10d or 16d nails on those materials.

Rim board failure
Rim board failure

Understanding that alternate fasteners are available for many connectors can help you pick the right fastener for you application. When you specify a connector, it is important to also specify the fasteners you require to achieve your design load.

Know Your Code

I attended a CFSEI and Steel Framing Alliance webinar last week entitled Specifying Cold-Formed Steel: Finding and Avoiding Pitfalls in Structural General Notes and Architectural Specifications. The presenter was Don Allen, P.E., from DSi Engineering, LLC, and he focused on issues specifically related to design and specification of cold-formed steel (CFS) in contract documents.

The first post I ever wrote for this blog was But I Don’t Design Cold-Formed Steel… I talked about how limited my initial experience was with cold-formed steel and how I was forced to learn it on the job when projects required it. During the webinar, I winced a few times recalling my first CFS project when Don mentioned why you should not do certain things — and they were things I used to do.

1997 UBC
1997 UBC

Referencing the “most current edition” of a standard was something I remember doing in our general notes, and the webinar mentioned why it is important to verify that specified reference standards are correct for the governing building code for the project. I first designed under the 1994 Uniform Building Code, and then used the 1997 UBC for many years after that. The Uniform Building Code was almost self-contained in that it covered gravity, seismic, and wind load requirements in Chapter 16, and then each of the material chapters had most of the design requirements in the code.

A significant change in the International Building Codes has been removing many of the design requirements and simply referencing the appropriate design standards. Whereas the UBC had methods for calculating wind loads, the IBC simply refers you to ASCE 7 for wind loads. Similarly, Chapter 19 of the 1997 UBC had many pages of concrete design requirements. Now, the 2012 IBC has just a few pages referencing ACI 318 and then makes several amendments to it.

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