Hangers for Ceiling Joists that Meet at Beam
I’m personally building our first house. I’m not really a carpenter or tradesman but have enough experience to get it done. Where I live, there are no codes, inspections, no permits, etc., besides electrical and my father in-law will be helping with that. I’m in middle Tennessee but trying to build things, where possible, to higher wind load areas. I’ve got a beam going through the middle of the middle of the house with joists sitting in hangers.
My concern is this – when the stick built rafters are loaded and trying to spread apart, are hangers really enough to prevent that spread? I’m attaching 18 ga. nail strips to every other one just in case. But I’m happy to do more. What is the code for something like this in higher wind areas?
Thanks for any help you’re willing to provide! I definitely don’t want my 2×10 rafters spreading my walls apart! 😄
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Without analysis, its tough to say for sure. That said, the 18 ga strips will help quite a bit. Make sure to fill every hole with a nail. The 1-1/2" "shorty" 10d nails will work fine for this, though 10d common will give a bit more strength. It looks like you've got some posts supporting that giant beam. If it won't get in the way, just a few posts up to the ridge will also do a world of good. FWIW, wind loading isn't generally the biggest actor in rafter spread. It's just the weight of the roof over time, and in cold country, snow loads. If you nail off the roof sheathing properly and clip the rafters down to the plates and wall studs, wind loading shouldn't be an issue.
I'll be sure to go back and add the extra nails, thanks! And good point about the spread with loading. I'll definitely be using clips at the outer walls as well as collar ties.
So the pictures are showing floor framing, and a second storey will be built on top, with stick framed rafters on top of that?
Depending on spans, you will want either a ridge beam or collar ties to prevent spread. If you go with collar ties you will create a small attic space which can be helpful for other reasons.
Looks like you used 2x4 for lintels at interior walls? Might be undersized.
So, the area above those ceiling joists will just be attic space. I currently have some osb up there to walk on while doing the rafters.
I do plan on using a 2x ridge board all the way down the middle of the house where the rafters meet at the top as well as collar ties. But that *only* prevents spread of the tops of the rafters. Rafter ties and/or ceiling joists prevent spread at the bottom. Since the bottoms of the rafters are tied to the walls and ceiling joists, it may want to pull those particular joists away from the middle ceiling beam, out of their hangers. In the rest of the house, the ceiling joists are essentially connected all the way across the house so they can't ever pull apart.
The interior walls and headers are 2x4. But in our situation, they're nearly all non-load bearing. Hard to tell from the pictures.
JellyBean
You have a good handle on how stick-built roof framing works so that's half the battle.
When I go to Simpsons website, they only list hanger capacities for uplift and gravity loads. This seems to imply that the hangers don't have much withdrawal capacity to resist rafter thrust. You could always call your hanger manufacturer to get more details, but I think you are right to be concerned.
When I am in a building with stand-alone rafter ties (not ceiling joists doing both jobs), I typically see a rafter tie every third rafter, so you may not need to strap every ceiling joist. May need to do an analysis, or hire a professional to do an analysis, to make sure the straps have the capacity for expected thrust loads, otherwise you may need to strap all of the joists to distribute the forces more.
Thanks for the reply, Huey. I am using Simpson hangers here. And it makes sense that they wouldn't specify withdrawal/pull-out as those diagonal fasteners are only attached in the ends of the boards. I'm sure I could lever those joists out by hand if I wanted to.
I contacted our local (next city over) codes department with details and pictures. They replied that "the hangers are code compliant but if you want to add strapping, that's acceptable as well". It blows my mind that hangers, in this usage, could be code compliant. But we also are not in a high snow or high wind area. So maybe that's why?
I may go ahead and strap all of the joists just for the sake of extra peace of mind. Worst case scenario, it makes it a pain to attach our drywall. 🤣
Another responder mentioned adding posts under the ridge board and I think I'll take this into consideration as well. Making it a semi-structural ridge board would likely help keep snow load from being able press down and out as much. But that sort of thing isn't common around here and I have definitely never done something like that. Don't reckon it'll be all that difficult or complicated though.
JellyBeanFTW,
You have done a good job analyzing the forces on the stick framed portion of the build and accounting for them on that portion of your framing, but both the walls and floor get covered by structural sheathing or sub-floor which turns them into structural diaphragms - and increases their strength exponentially. Once that is on what at you have there - especially if you make sure to the sub-floor overlaps at the beam - is if anything overbuilt. I would stop now and not worry about it anymore.
I definitely would not add posts under the ridge board. In engineering there is no "semi-structural" You don't want a hybrid structure which starts to transfer loads to the interior beam in ways you can't predict. Size your rafters appropriately and you will be fine.
Malcolm, I'm not sure why I can't reply to your comment. But I appreciate it!
So, unfortuantely, the tops of those ceiling joists will not be getting structurally sheathed like walls and roofs do. The reason is this - the joists are 2x10. The beam is roughly 5x14. So there's no way the tops of the joists can be lapped with sheathing to prevent spreading. It'll just be attic space.
Thanks for the tip on not adding things that may cause unpredictable results. I have slightly oversized the rafters and they'll be 2x10.
JBFTW,
I missed that about the beam. I think you are on the right track adding strapping to the undersides.
Good luck with your build. From what I can see it looks like a nice site.
If the attic floor is still only tacked down, you can install sheets of plywood spanning across the beam and nailed on both sides. That will also add a lot of tensile strength to the assembly.
Hello Peter. Thanks for your reply. The ceiling joists are 2x10 and the beam in the middle is 14 inches high. So using sheathing to overlap that beam will be impossible. The sheathing I currently have tacked up there is going long was -next to- the beam and not over it.
I notice in your big triple header, I see only two through bolts joinging the members of that beam. Is that all you're using? Only two bolts isn't enoughtto properly share the load between all three members of that beam unless you've also glued it together. Note also that those two bolts are absolutely not enough to handle tension through the joists -- which is what will be keeping things from spreading -- and your extra straps will greatly help with that.
I would put straps on every joist for some extra insurance with tension. I wouldn't trust the hangers for that since the hangers are really only for vertical loads, not tension along the length of the joists.
If you're concerned with the structure, it's probably worth having an engineer do a review. Since you don't need sealed drawings or anything in terms of submittals, you really need more of an eyeball Q and A session with the engineer, which shouldn't be very expensive.
Bill
Thanks Bill. The "triple header" has two bolts in each end and a bolt every 16 inches alternating high and low. A total of about 21+ .5" bolts holding the three glu-lam beams together.
Your thoughts on the hangers and straps are very similar to my own.
Posts under the ridge could add a load to the beam that it's not designed for. Speaking of that, what is the beam (LVL?) designed for? And by whom? If you had it sized by the lumberyard, it's probably designed for the floor load only. Not sure what the the through bolts are for, but make sure you follows the beam manufacturer's schedule for fastening the 3 plies together.
Zephyr7's suggestion of getting an engineer out to look at it is a good one. Just make sure the engineer has real world experience with light frame construction, and a working knowledge of the Simpson catalog, or your "solution" could end up being bigger than your problem. There's a lot of hardware that might work for you- angled straps, deck tension ties, etc.- but you need someone who can look at it and understand the loads and how to address them.
Thanks for the reply, Joe. I sized the beam myself to accommodate a light floor load plus a little for safety margin. When I was thinking of adding posts, I was considering adding them mostly on the ends where there are support walls underneath - which has a support wall underneath that in the basement. But you make a great point, no point in stressing beam if I didn't account for the extra load. And it's three 1 7/8" x 14" glu-lam boards if that helps. The through bolts are only to keep those three boards together. Probably a bit over kill. But so is the rest of the house. ( :
I'll call around and see if any engineers are willing to come out for a modest fee. Last time I contacted one just to ask a question about a specific header size, he wanted $350 to answer the question. Ended up looking through tables until I was satisfied.
That's awfully steep to size one header. $350 gets two hours from my structural guy here in MA. As Malcolm Taylor pointed out above, if the floor sheathing laps the beam, you may be all set.
I thought it was steep as well. It was worth my time to just do it myself. 😂 Unfortunately, that beam is 14" tall so there's no way of lapping the top of the joists with sheathing as the beam sticks up above the joists by about 3-4".
JBFTW,
With the construction boom here I have been having a terrible time getting a structural engineer to look at anything less than a full house review. I've been doing much as you have and instead putting the money into a beefed up structure, rather than professional fees.
I'll warn everyone, speaking as an engineer (although I'm an electrical engineer, not structural), that the engineer's job is to catch the weird and unsual issues, not to just follow code. That's why the code has all the exceptions for "under engineering supervision". The way I usually explain this to customers is "an oil refinery has a lot of pipes, but you don't hire a plumber to build one".
Just "beefing up" the structure doesn't necessarily mean you've made it safe. There may be other forces at work that you didn't allow for. An example from the OP's house: you could go up to 2x12s on the floor joists, and add two more glulams to the big beam, and none of that would address the issue of tension -- the force trying to pull the joist out from the hanger along it's length. You would, in that example, have beefed up the structure a lot, but none of your "beefing up" has addressed the actual problem. That's the risk you take doing anything unusual and not involving an engineer.
As I've said here before, if you have ANY doubt with the structure, consult with an engineer. Be safe, always. The consulting engineers I work with will do a full plan review for a small project for under $1,000. That's not much money compared to the cost of a house, and it's downright cheap when you consider that if you miss something on the structure, you could end up killing someone someday. Please don't take chances here.
Bill
IN a high wind area, you also want to add strapping across the ridge, attached to the top of the rafters on both sides. High winds can make a roof pop open at the ridge. Rafter ties placed in the top 1/3 of the rafter will do the same thing, but cut down on walking space.
Thanks Pete. I had planned to do collar ties towards the tops of the rafters. Thankfully it's just attic space. But I think I'll be able to walk underneath them (6'1") after installation so all is good. I had thought about doing the strapping across the tops of the rafters and over the ridge board. But I think I'll allow that extra real-estate for fastening the sheathing all the way up. ( :