ELEDSALL
New Member
Posts:3
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| 08 Feb 2008 05:27 PM |
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I need some feedback on hanging open web floor trusses to the Simpson ICF connector. Simpson's instructions show a single ledger board but my truss guy says to hang to at least 3.5" ledger. Comments please. |
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dmaceld
Veteran Member
Posts:1465
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| 08 Feb 2008 06:25 PM |
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I sure hope there's no problem doing it your way. That's what I'm planning on using, ICFVLs spaced at 4' o.c. with a 1 3/4" x 7 1/4" LVL ledger, using Simpson IUS2.37/9.5 face mount joist hangers to hang 2 3/8 x 9 1/2 I-joists. My plan has been reviewed by two lumber estimators, a floor joist distributor, and the building inspector. No one raised a question.
You sure he's not thinking in terms of solid wood? If so maybe that's why he's saying 3.5 ledger. Use an LVL, much stronger and no shrinkage problems.
3.5 inch thick ledger creates a potential for the screws to bend down more easily, especially if the wood is a bit soft. You know, a long cantilever beam bends easier than a short one, the screws being cantilever beams.
The installation instructions I have for I-joists states that the minimum bearing length is 1 3/4" at the ends and 3 1/2" intermediate. I wonder if your truss man is confusing intermediate support length with end support length requirments.
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Buntly
Basic Member
Posts:162
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| 08 Feb 2008 06:48 PM |
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I do know that if you use a 2x ledger vs an lvl there is a difference in the capacity of the hangers which hold the joists. I'm sure this is still the case unless Simpson revised their catalog for 2008. Any nail that penetrates into a 1 1/2" carrying member (ledger board) must have a reduction to the tabulated capacity of the hanger. For example, if the tabulated value for your hanger is 2000 lb, you must multiply this value x .64 (i think) if you are tying into a 1 1/2" thick member. In other words there is a reduction because the ledger is only 1.5" wide. This reduction applies about 95% of the time to face mount hangers if a 1.5" carrying member is used. Read the fineprint on the bottom of the page once you decide what hangers you are using. If you are using the ICFVL-CW, there should be no problem, but if you are using the ICFVL-W, then you may have an issue. I typically use a 2x10 SP ledger with 14" deep floor trusses and I use a simpson HU46 face mount hanger. Ideally you would install a double ledger as simpson shows in their catalog. You would then use top chord bearing floor trusses and eliminate the hangers all together. I have pictures of this I will put up if I can figure my friggin' scanner out. I think there is some confusion between the truss company and your application with respect to the bearing. The only way wou would need a ledger that wide is if the reaction of the truss was large enough to cause crushing of the grain of the wood. This condition very rarely governs the design of a floor truss.
Bunt
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 Attachment: floor example.pdf
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| Bunt |
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irnivek
Basic Member
Posts:229
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| 08 Feb 2008 08:21 PM |
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Top chord or bottom chord bearing open web truss?
Kevin |
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Quantum
Basic Member
Posts:255
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| 08 Feb 2008 08:34 PM |
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Top-bearing is bad news with an ICFVLed ledger. Although to me, ICFVL's are bad news in any case. (Are we talking about wood or steel open-web?)
Joist hangers for TJI (is this what you mean by I-joist, Mac?) are to Code, but I just don't like ICFVL. Sheet metal sticking all the way through the foam, a weak point in seismic, and susceptible to fire. Yeah they're easy, and I install them when specced... but not for my house.
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dmaceld
Veteran Member
Posts:1465
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| 08 Feb 2008 08:43 PM |
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Posted By irnivek on 02/08/2008 8:21 PM
Top chord or bottom chord bearing open web truss?
Kevin What are you asking, or questioning?
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| Even a retired engineer can build a house successfully w/ GBT help! |
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walltech
Basic Member
Posts:390
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| 08 Feb 2008 08:44 PM |
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Eledsall: Sounds like top bearing. If this is the case my local trussers would require 3". Bottom bearing would be less but I'm positive your talking top.
Dave |
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Buntly
Basic Member
Posts:162
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| 08 Feb 2008 08:45 PM |
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I don't like em either. I know the numbers work out and all, but that's in a perfect world (is concrete consolidated, are all screws installed properly, are the connectors fully embedded, etc) . Plus after ya get done installing about 10 of those things, your hands are numb. It's also real fun when you have a joist hanger land where a connector is. I don't know if they improved their screws recently, but last time I used them seems like I stripped about 1 out of 5 screws. They call them self drilling, but I had to predrill the ledgers and even then I still had problems. I had to have simpson send me more screws. Too much room for error for me. Nope, I don't like em.
PS, I wonder if Simpson will warranty if the ledger connector is used in Logix with 2.75" foam? Seems last I looked they were spec'd for 2.25" foam.
Bunt |
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dmaceld
Veteran Member
Posts:1465
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| 08 Feb 2008 08:55 PM |
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Posted By Quantum on 02/08/2008 8:34 PM
Top-bearing is bad news with an ICFVLed ledger. Although to me, ICFVL's are bad news in any case. (Are we talking about wood or steel open-web?)
Joist hangers for TJI (is this what you mean by I-joist, Mac?) are to Code, but I just don't like ICFVL. Sheet metal sticking all the way through the foam, a weak point in seismic, and susceptible to fire. Yeah they're easy, and I install them when specced... but not for my house.
As I understand it, TJI is a brand name, or acronym, originally for Trus-Joist I-joist, now I-level I think. I-joists are mfr'd by I don't know how many outfits now. Seismic I'm not worried about. If my house burns ICFVLs will be least of my worries!! Don't underestimate the strength of sheet metal. After all, your car and pickup are all sheet metal and plastic, and I doubt any of it is 14 gauge. Maybe the main frame in the pickup is.
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| Even a retired engineer can build a house successfully w/ GBT help! |
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walltech
Basic Member
Posts:390
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| 08 Feb 2008 09:00 PM |
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Bunt, ICFVL's are not my favorite either, but a cordless impact (not hammer drill) is non fatiguing on the wrist and will not burn up screws like a non impact. Also for those reading this, never use a LVL even with an I joist or you will have to drill all the holes. We recommend Hem Fir, and top hung hangers.
Dave
p.s. Mac, snap a chalk line at the bottom of your rim joist and set a skill saw at 2 7/16 and cut on the line. Insert a meta fire-stop 3" by 16ga to negate the potential problem for fire if you feel it's necessary for piece of mind.
Dave |
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dmaceld
Veteran Member
Posts:1465
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| 08 Feb 2008 09:12 PM |
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Posted By Buntly on 02/08/2008 8:45 PM
but that's in a perfect world
It's also real fun when you have a joist hanger land where a connector is. My house plans and house will, of course, be perfect!!! :-) I just looked at my drawing. I've got all the ICFVLs located between joist hangers. Now all I need to do is build the wall according to plan, right? Yeah, I can see your eyes rolling now!!! It'll be interesting to see just how close to plans it all does work out. And bunt, when I have a hanger over an ICFVL I know I will hear you saying, "I told you so!!" |
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Buntly
Basic Member
Posts:162
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| 08 Feb 2008 09:21 PM |
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I'll try a cordless impact next time. Seems like you would need one hell of a charger to keep up with battery situation though. Dave, are you saying that if an lvl is used as a ledger that you need to predrill all the holes for th icflc-cw? As I mentioned earlier I predrilled when I used 2x10's for ledger. This however made it even more difficult to install the screws because there was no material for the threads to pull the screw through and push into the icflc . I found that a 3/16" drill (i think that was the size) worked best. There was enough material removed to make the screw go in easily, yet enough for the threads to "bite". Also, another reason I dislike hangers is that if not installed properly, squeaks may be an issue.
Bunt |
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Quantum
Basic Member
Posts:255
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| 08 Feb 2008 09:26 PM |
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From Simpson's Load Table
2. Loads apply to ICF foam thicknesses of 2 3/4" or less. Well, I don't care. Too weak. |
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Buntly
Basic Member
Posts:162
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| 08 Feb 2008 09:28 PM |
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Mac, sounds like you're doing a thorough planning. I'm sure this will eliminate alot of headaches. I've only had hanger land on icflc once,.............(actually twice,.... first and last,.....hee hee hee!). We had to move a truss for plumbing purposes and happened to land on icflc. I have however seen this happen to others quite frequently because of a lack of planning.
Bunt |
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walltech
Basic Member
Posts:390
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| 08 Feb 2008 09:35 PM |
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Buntly, actually a impact will put 3 times as many screws in as a reg drill/driver, and will be hardly felt on your wrist. No you will not need to drill a 2x material with the impact but a lvl gums up and snaps screws.
Quantum, as I mentioned I'm not a big fan of ICFVL's either. We had at years end experimented with 6" basements to 4" uppers supporting the ledger on the concrete lip created on a 6" taper to 4" upper. So far so good! But the jigs not up yet.
This has alleviated the fire-blocking but created a few electrical issues.
Dave |
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Buntly
Basic Member
Posts:162
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| 08 Feb 2008 09:48 PM |
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I like the transition idea. I have seen it on several jobs recently. I am not thrilled about working with 4" cavity walls however.
Bunt
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Chris Johnson
Advanced Member
Posts:878
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| 09 Feb 2008 12:26 AM |
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Use AB's guys, set the ledger with the hangers already installed before the pour, no joists hitting AB's cause the layout was done before the installation, helps keep the wall straight.
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| Chris Johnson - Pro ICF<br>North of 49 |
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dmaceld
Veteran Member
Posts:1465
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| 09 Feb 2008 12:31 AM |
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Posted By Buntly on 02/08/2008 9:28 PM I've only had hanger land on icflc once,.............(actually twice,.... first and last,.....hee hee hee!). We had to move a truss for plumbing purposes and happened to land on icflc.
I did just this the other day, except it was with the CAD drawing where it's a lot easier to do! Had to add a joist to accomodate toilet plumbing and then repositioned a connector, and added one. |
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Quantum
Basic Member
Posts:255
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| 09 Feb 2008 08:00 AM |
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Chris I agree about using the old-fashioned way, but haven't hung the ledger before the pour for two reasons:
- The ledger gets in the way of bracing;
- On pour, the wall settles and the ledger may not end up being level.
I leave it for the framers. |
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Buntly
Basic Member
Posts:162
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| 09 Feb 2008 08:28 AM |
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A few years ago, we used top chord bearing steel floor trusses for a job (same could be done with wood). It rained for days and cement trucks could not get back to site. To keep going we screwed a 2x6 around entire perimeter of bldg and the put a 2x4 brace from ledger to footing about every 4 or 5' to support the temporary ledger. We then set the trusses on the ledger which was perfectly level. We stacked 1 more course above the trusses and then poured. We set the steel i-beams and put the steel deck on as well. We screwed the steel floor trusses to the ledger and this held the wall perfectly plumb during the pour and we also had a deck to walk on as well. If I recall, there was little if any adjustment necessary during the pour. We had to be a little more delicate when installing the joists on unpoured walls, but once done, it sure was nice. Circumstances permitting, I wouldn't hesitate to do it again.
Bunt |
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