My crew just started framing for a local developer who acts as his own GC. Lots of small split levels with 12-15″ sections cantilevered over the lower wall 1-2′. This guy wants to have 2×6 joist hangers installed on top of the cantilevered joists where they butt into the beam as well as the 2×10 hangers beneath. Tedious, time consuming, hard to get the t&g tight, and not something I’ve seen or heard of before.
Anybody else with experience in this area?
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Replies
It is a reasonable request on his part.
Some believe it is necessary.
Sounds like there's some logic in his approach. However, if the joists are spiked thru to the beam properly - ie not just 1-1/2" JH nails but 3" toe-nails - then you may convince him this will counteract any (unlikely) upthrust. But, if he insists, look at Simpsons for straps that would do. If you consider that the JHs will resist turning/twisting motion, then there's no reason why you cannot splay the smaller hangers at, say, 45 degrees, so that you don't have to nail thru the bigger JHs at the same time.
But, since he's paying - humour him.
All the best...
To those who know - this may be obvious. To those who don't - I hope I've helped.
In a cantilevered situation you can get either a downward reaction or uplift, depending on what part of the floor is loaded. (I can go into more detail if you're interested)
I've called hangers out this way on floor trusses before. Sometimes it's the only thing that works.
There probably isn't any reason you couldn't use a 2X6 hanger both on top and underneath. The reactions on floor joists in these situations are generally pretty small. That would save you a few nails.
Another option might be to take the cantileverd joists back farther before you tie them into a beam. That lessens any uplift loads that might occur. The 2X10 hangers you're using will have a rating for uplift loads. If you move the beam farther back the uplift might be low enough that one hanger would take care of it.
Interesting responses. I had assumed that the uplift rating on a 2x10 hanger was more than enough for any force that would be present here. Actually, by my own (rough) estimates, the weight of the joists and sheeting over 12' easily overbalances the weight of the glazed wall 16" past fulcrum. Theoretically no roof load since it's in a gabled end. We don't usually have latitude to alter the framing plan since we get it complete from the architect and they seem techy about those sort of things. Also, for more practical reasons, the beam that the cantilevered joists butts to usually also forms one side of the stairwell for the split level. This last house was a 16" overhang with CL of the beam at 12' from the outside wall. Last laugh is the developer's since he's paying to frame by the square foot. Maybe time for me to swallow a live and learn pill.
"...the weight of the joists and sheeting over 12' easily overbalances the weight of the glazed wall 16" past fulcrum. Theoretically no roof load since it's in a gabled end."
You didn't mention those things in your first post.
You're correct that the gable end doesn't add much load at all. Maybe a couple hundred pounds per joist max.
The significant thing in my mind is the distance back to the carrying member. In this case you say it's 12' - That's a heck of a lot. If you have 200# sitting on the end of a joist that's cantilevered out one foot, the uplift is only about 1/12th of that with a 12' back span. You could probably hold that much with one nail.
If you cantilevered out a couple of feet, your back span was only 4' or so, and you had significant roof load, you could have some serious uplift. But that's obviously not the case here.
You didn't mention what hanger you were using. Just for the heck of it I looked up an LU210 in my Simpson book. It shows an allowable uplift load of 735# for SYP/DF. An LUS210 has an uplift load of 930#.
You might try showing the guy the Simpson tables, and point out how long the back span is. Or go with a pair of 2X6 hangers if he insists on 2 of them. At least that way they won't overlap, and you won't have so many nails.
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