Joist Hanger Installation Defects
February 2nd, 2010 | 8 comments
Just a little over a year ago, I took a class put on by one of the largest manufacturers of metal brackets, Simpson Strong-Tie. That class was a real eye opener – I realized afterwards that just about every deck that I inspect is constructed wrong. Not all of the installation defects are major, but they’re always worth pointing out. Today I’ll talk about one of the most common installation defects that I find with joist hangers in the Twin Cities – improper nails.
You thought I was going to say missing nails, didn’t you? Too easy, too obvious.
Wrong Nails If the wrong nails are used at a joist hanger, it won’t perform as intended. To know what nails are supposed to be used, you first need to know what joist hanger you’re working with. The most common joist hanger I find on decks is a LUS28*. This joist hanger can be used with 2×8 and 2×10 joists. Now that I know which hanger I’m using, I can go to the Simpson Strong-Tie web site to find out what fasteners are specified. To see the full page I’m looking at, click here.
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As you can see, this hanger requires 6-10d nails + 4-10d nails. The big defect that I often find is that 10d x 1 1/2″ nails are used in place of 10d nails. If you look down on the far right column of the above chart, you’ll notice only a few hangers will allow a 10d x 1 1/2 nail. So what’s the difference between the two? Quite a bit! The photo below shows the two next to each other.
Now here’s what the nails would look like if driven in to the floor joist. You can see that the smaller nail isn’t long enough to even begin to penetrate the ledgerboard. Click the photo for a blowup.
The really crazy thing about this is that the nails that are so much smaller are actually called “Joist Hanger Nails”! They’re called joist hanger nails because that’s about the only thing they’re good for… but they’re usually not even good for that. If you go to Home Depot and you look at their joist hanger display, you’ll probably find boxes of joist hanger nails sitting with the rest of the joist hangers, and no other types of nails. I’m pretty sure that’s why these nails get used improperly so often.
To identify these “Joist Hanger Nails”, all I need to do is look at the head of the nail. They all have a big “10″ stamped on them. Standard 10d nails don’t have this.
How serious of a problem is this? The manufacturer will allow these nails in to the header, but the total load will need to be reduced to 64% – a huge reduction. The manufacturer does not allow these nails in to the joist. I sent the manufacturer two separate emails to find out what the reduction factor would be if they were used in the joist, but after ten days, no reply.
I meant to make today’s blog about all of the different defects that I find with joist hangers, but this one defect just ended up being enough for a full blog. More on joist hanger defects later.
* Joist hangers meant to be used outdoors or in contact with treated lumber will often have “Z” at the end of the model number. In my example, the joist hanger used for a deck would actually have a model number of LUS28Z.
Reuben Saltzman, Structure Tech Home Inspections - Email - Twin Cities Home Inspector
Reuben Collins
February 3, 2010, 4:20 pm
So the nails into the header are driven directly perpendicular to the header, but the nails into the joists should be diagonal so that they also hit the header? If that’s so, then why do the 1.5″ nails result in a 36% loss? Any nails longer than 1.5″ would just stick out the back side of the header anyway, right?
Reuben Saltzman
February 3, 2010, 5:12 pm
Properly sized nails will go through the header and then in to the rim joist of the house, where they’ll have even more ‘holding’ power.
David
March 12, 2010, 3:31 pm
You are partially correct. Yes, 10d nails need to be used on the diagonal, but the “joist hanger nails” are used to attach the joist hanger to the header. The reason they are special is because they have the strength of the longer 10d nails, but are shorter so they don’t stick out. Therefore, the name is correct.
Reuben Saltzman
March 12, 2010, 6:36 pm
Hi David, thanks for reading. You wrote
“Yes, 10d nails need to be used on the diagonal, but the “joist hanger nails” are used to attach the joist hanger to the header.”
That’s not correct – the manufacturer specifies full 10d nails in to the header. Just check the chart that I included. As I mentioned towards the end of my blog, the manufacturer will allow 10d 1-1/2″ nails at the header, but the load capacity gets reduced to 64%.
Jim Kaczmarek
May 14, 2010, 12:29 am
Please clarify. When you have a single 2 x 8 rim joist (not a header which is usually connected to the house) which have several joists each connected to the rim joist with a LUS28 hanger, you need to use 10d by 3″ long nails? I am not talking about the diagonal nails, but the nails that would be perpendicular to the 2×8. Any nail longer than the 10d x 1-1/2 inch nail would penetrate through the single 2 x 8 rim joist and not add to the strength of the connection.
Was the use of Strong-Tie screws talked about in your class? If so, any comments on using Strong-Tie screws versus 10d joist nails.
Reuben Saltzman
May 14, 2010, 5:44 am
Hi Jim,
You could still use 10d 1-1/2″ nails to attach the hanger to the header, but you would need to calculate the appropriate load reduction. Standard 10d nails should still be used in the joist.
There was no mention of the screws at the time I took the class, but they look like a great product. http://www.strongtie.com/products/connectors/screws-loadrated.asp
Harvey
June 28, 2010, 7:34 pm
Hi Reuben,
Like David said above, the 10d nail from a joist hanger nailer can be used at the perpendicular attachment of the joist hanger to the header provided they are stamped 10d. A 10d nail is a 10d nail no matter the length. However, the reason they specify full length nails is only for the diagonal installation. Other wise, like David said, the perpendicular nails will stick out of the header material and not provide any extra shear strength. Because the nail is longer it does not affect the shear load it will break at, it depends only on the diameter.
Reuben Saltzman
June 29, 2010, 4:22 am
Hi Harvey,
The problem with 10d 1-1/2″ nails isn’t their shear strength – you’re correct, that doesn’t change. The problem is their holding strength. I received this email on March 25th, 2010 from a Simpson Strong-Tie rep:
If a nail is stamped 10D, it will be a 1-1/2″ nail. Full size 10D nails don’t have that stamp on their heads.
Also, I stopped by Home Depot and took a photo of the nails that they had sitting next to the joist hangers; while Curt was correct, they’re not labeled joist hanger nails by Simpson, they ARE labeled as joist hanger nails by Home Depot. You can see a photo below.
Thanks for reading.