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  1. #1
    Join Date
    Aug 2004
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    WV, Cold Climate w/ wind, HDD 7136, 56" avg. precip.
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    403

    Default Deck Ledger Bearing & ICF

    Looking at deck ledger bearing on ICF walls and how to detail. Decks are only 10 foot joists length so loads are not much on the ledger, but the ledger will be bolted to band/rim board and the rim board will sit on sill plate but directly over foam and not concrete. So other than the sill plate their is no direct bearing for the rim board. (detail attached)

    I sent this off to my engineer to detail and he said that he was going to send me the detail on Monday, but basically he was asking for the anchor bolts on the sill to be reduced to 4' spacing and then to run 5" ledger lock screws through both rim boards into the I-joists ends and then to site fabricate a "tapered top" on the ICF to create a concrete ledge. (detail attached only shows tapered top ICF)

    This has got to be a common detail with ICF's and Deck Ledger attachments. How are you all handling this detail with consideration of bearing ledger/rim board attachment over the foam of ICF?
    Attached Files Attached Files

  2. #2
    Join Date
    Nov 2004
    Location
    Boston, MA
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    4,894

    Default Re: Deck Ledger Bearing & ICF

    If you are asking about the taper in the ICF- yes it is common. I know there are some ICF manufactures that make the tapered block as well. Your taper looks pretty deep, you might be cutting form ties. You could technically cut away the top 4" of form all together on the outside, then form the concrete all the way to the exterior face of the form creating a nice beefy concrete ledge. You would loose a bit more insulation.
    "First we finish the game, then we’ll deal with the Armada!"

    Sir Frances Drake

  3. #3
    Join Date
    Jun 2004
    Location
    Branford, CT 06405
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    3,675

    Default Re: Deck Ledger Bearing & ICF

    It appears your engineer has provided what he/she believes is appropriate for the specific condition. I'm not sure if you are questioning the detail or looking for an easier solution?

    In general I like the detail except I don't quite see the ledger lock into the I-Joist end detail as being sufficient(for me). I would provide infill on the I-joist, then a 3' solid sawn pad on each side of the i-joist so the whole assembly is tied to the I-joist, NOT just into the end of the top and bottom flanges. The ICF flare, common practice depending on conditions, will provide all the vertical bearing you need, you have not provided info as to height above grade so as hgt increases, the lateral forces also do, and quickly!

    Flashing and membrane protection is critical in your detail. Do it carefully!
    Take Care

    Jim

  4. #4
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    Default Re: Deck Ledger Bearing & ICF

    Let me throw a bone to all the old ICF guys -

    Tucker, why stop with the ICF at grade? Go all the way to the roof!
    "First we finish the game, then we’ll deal with the Armada!"

    Sir Frances Drake

  5. #5
    Join Date
    Jun 2004
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    Branford, CT 06405
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    3,675

    Default Re: Deck Ledger Bearing & ICF

    Because I'm guessing this will be an addition, so the details which most mfg provide have somehow disappeared?

    I notice I said pad both sides of the joist above, but one side would be adequate, once attached securely to the i-joist side.

    I use 3/4" galv or ss threaded inserts with epoxy when I use ICFs all the way to the roof! The 3/4 is because of the 2.5" foam, but then I also add spacers!
    Take Care

    Jim

  6. #6
    Join Date
    Aug 2009
    Location
    St. Paul, MN & Northern WI
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    275

    Default Re: Deck Ledger Bearing & ICF

    Tucker:
    I think Ted and Jim have it right, but I would go even a bit further in discussing the problem. The thing that makes you nervous is that the rim jst./board takes a good share of the ext. bearing wall load down to the sill plate, and acts as a guillotine on the sill plate. This is a very weak way to be loading the sill plate, and you have this condition all the way around, not just at the deck ledger which just adds more load to the problem. Do you have the double rim board all around, or just at the deck? Given the way the ext. bearing walls are loading the I-jsts. I would assume that the I-jst. manuf’er. shows squash blocks on the I-jst. webs under the brg. walls. You should put them in. The I-jst. manuf’ers. frown on nailing or screwing into the ends or sides of the flanges because of the potential of splitting the flanges and seriously damaging them, strength wise.

    That sloped cut on the outer shell of the ICF blocks will be fairly difficult to do. Why not just cut the face shell off the ICF block and form and cast a brick ledge the full height of the top course, to match the ext. plane of the rest of the ICF blocks. Ted’s 4" is probably o.k. but seems a bit less depth than I’d like to see, and not as easy as just taking off the whole face shell. Although, this might change a little from ICF supplier to supplier. That loss if insul. is a small percentage of the total wall area. It seems to me that I’ve seen some ICF blocks which do allow the bump-out for casting a brick ledge and the like.

    Regarding tying the ledger back into the floor diaphragm, I generally agree with Jim, and would not screw into the end of the flgs. of the I-jsts. Screws and nails into end grain have very low values, plus the splitting issue. I would take a piece of 2x10, or some such, standing btwn. the I-jst. flgs., like a squash block; standing on the bot. flg., with a 1/8" or so gap under the top flg.; glue and screw this to the I-jst. web, screws through the osb web into the 2x, to pull them together; then use your 5" long structural screws into the edge of this blocking. This gets any lateral loads (pull-off loads) into the I-jst. webs and up into the floor diaphragm. But, also remember that the deck jst. hangers do not show an allowable load (or it’s very small) for pulling the jst. away from the ledger along the jst. axis, so in short, these do not do a good job of tying the entire deck into the bldg. w.r.t. lateral loads out on the far edge of the deck. Each deck arrangement should be analyzed to determine if a more elaborate means of tying the deck to the bldg. is needed. What happens is that a lateral loading on the deck will tend to pull one corner of the deck away from the ledger and bldg. while pressing the other corner into the ledger and bldg. And, both corners or either corner might be the tension corner. This tension reaction is usually fairly concentrated and applied at the first interior deck jsts., not just the edge jst., so as to involve adjacent deck jsts. through the decking. Without attention to this condition, when the deck racks it starts to pull the edge jst. (deck rim jst.) away from the bldg., it fails, and then the first interior deck jst. is pulled off, etc.
    Dick Hackbarth, PE
    RWH&AI, Consulting Engineers

  7. #7
    Join Date
    Aug 2005
    Location
    Boise, Idaho
    Posts
    558

    Default Re: Deck Ledger Bearing & ICF

    The taper top is common and is easily formed either with pretapered ICF blocks or by cutting the taper in a standard block with a sawzall and long blade. If it's just a detail where the deck joins I normally wouldn't order taper top blocks and just cut them on site, but if the detail is carried around the entire perimeter then it makes sense to order the taper tops.

    I think the engineer is on crack if he is suggesting screwing into the ends of an ijoist! lol Even squash blocks are nothing to be putting a ledgerlock into. However, I see that he's just trying to get a little better connection between the joists and rim/ledger and that is easy enough to do by fitting in blocking (even double thickness blocking) between joists that is toe nailed into the squash blocks. More pull out resistance than that and I'd think he'd want one of the simpson siesmic brackets that are through bolted to the rim/ledger and clinch nailed to plywood fillers on both sides of the Ijoist web.

    If you are unfamilar with how a taper top is effected during the pour you'll want to be sure and run an additional full length board on the outside of the blocks to prevent an outward puckering of the foam where it's thinnest, especially if it's a thick mix that you have to vibrate a lot. I like a thick mix and large agregate so my foam really takes a beating, but I've never had a pucker problem if at least a 2x6 is run along the top of the taper tops.

  8. #8
    Join Date
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    WV, Cold Climate w/ wind, HDD 7136, 56" avg. precip.
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    Default Re: Deck Ledger Bearing & ICF

    Thanks for the discussion and points. I will discuss w/ the engineer.

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