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Thread: Deck Design - Joist and Beam layout

  1. #1

    Deck Design - Joist and Beam layout

    I've been researching deck construction and designing it for the past year or so (on and off). It looks like I'll actually be able to put it in this summer.

    I have a question concerning the layout of the beams and joists.

    Everything I've read talks about attaching a ledger to the house, running a beam(s) parallel to it, then hanging joists from the ledger (and either setting the joists on the beam or hanging them from it). With this configuration, the decking runs parallel to the side of the house (unless, of course, you lay it angled).

    I want to have the decking run perpendicular to the house. Is there any problem with having everything turned 90 degrees (beams attached to ledger, etc.)? I don't see why there'd be a problem, but I figured I'd better ask rather thatn find out the hard way.

    Thanks for the help.

  2. #2
    Join Date
    Jan 2007
    Location
    43 Norway Spruce Street, Stittsville, Ont, Canada
    Posts
    64
    A question for you ...

    Is there any reason (building code etc.) why the deck has to be attached to the house? If you wanted to turn your deck 90', would it be possible to put the deck on posts sunk below the frost line, orient the headers and stringers to fit the way you want the deck boards to run, and leave the assembly separate from the house?

    Just a thought.

    cheers
    Last edited by John Bartley; 03-10-2008 at 5:28 PM. Reason: removed superscript code

  3. #3
    I'm in a rural area, so I have no authorities to answer to on building anything.

    The main reason to not make it seperate from the house is that I'm going to have it right there at the house, so why not use it as part of the structure?

    Then again, maybe building it freestanding would be easier than drilling all those holes in the foundation to mount the ledger. I'll check that!

    Thanks for the comment. It may have just made my life easier.

  4. #4
    Join Date
    Dec 2006
    Location
    Kanasas City, MO
    Posts
    1,787
    Not having a ledger board will also make one less spot for crud to sit. The top of the ledger against the house is a famous place for leaves, dirt etc to become lodged, stay wet and rot rot rot....... if you build freestanding you can leave enough of a small space there for "stuff" to fall through versus get hung up.
    FWIW, when I built my deck last spring, I ran flashing over the entire "top" surface (and ran a FAT bead of caulk along the ledger before laying & attaching the flashing) of the ledger in an attempt to make this spot not rot out as usual..... or at least not as fast.

    Greg

  5. #5
    Join Date
    Feb 2003
    Location
    Leesville, SC
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    2,253
    Guy,

    In this part of the country, most deck boards are ran perpendicular to the house. A treated 2X8 or 2X10 is fastened to the floor sill of the house with at least 1/2" bolts and nuts. You also have to install a galvanized flashing between the treated 2X8 or 2X10 and the floor sill. The joist for the deck are secured with joist hangers or set on top of a 2X2 rat sill. One contractor likes to run his decking boards perpendicular to the house with a slight fall on the deck so water will run away from the house.

    Perpendicular or parallel to the house is your personal option for what you think will look the best and work for you.

  6. #6
    That is a good point. In my case, however, I planned for the deck to be there when I built the house. There ledger would be tucked under the sheet metal finished vinyl siding.

  7. #7
    Join Date
    Apr 2007
    Location
    Birmingham, AL
    Posts
    263
    More than 20 years ago I helped my father build a deck in just the manner that John described. The deck is not attached directly to the house, it only butts up against it. All these years later that deck is still solid as a rock. We didn't have to worry about a frost line since I grew up in central Georgia, but we did have to contend with digging dozens of post holes through red clay. That stuff is just about as hard as concrete. The only downside to building a deck this way is that it will require at least twice as many support posts, but I think the resulting deck is much stronger.
    Last edited by Tim Thomas; 03-11-2008 at 11:02 AM. Reason: typo
    If I could ever finish working on my shop, maybe I could find the time to start working in my shop.

  8. #8
    Guy

    I built a pressure-treated deck exactly as you describe it in the first house my wife & I bought when we got married. That was 26 years ago and it is still standing in good condition. It is 30' wide (the ledger plate as well) and extends out from the house in an L-shape about 15 feet. I used a ledger board against the house, and ran joists off of that with beams parallel to the house. No problem. The key I believe is to get the ledge plate and jointing SOLID. Everything will stem from there. The only problem had was one I created - I planted a tree at one end and built the deck around it. A maple, and it grew much faster than I thought it would. The last time I looked it (about 2' dia.) it still had a few inches to go before it hits the decking but it appears to have slowed down.

  9. #9
    Join Date
    Oct 2006
    Location
    Mazon, Il
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    375
    Actually, Guy, you have no choice here. You must make a free standing deck.

    For the decking to run perpendicular to the house, your joists must run parallel to the house. You know that.

    Your pre-planned “ledger”, under normal circumstances, would be at the same height as your joists… and a simple matter to hang perpendicular joists off of. Your beaming would also have run parallel to the house. But all this is changed, now.

    You can still use the ledger if you want, but only to attach the ends of your decking to. I wouldn’t do it that way, but you could. It’s no big deal. You just need extra posts along the house to support your beaming. How many and how far apart will be determined by your beaming and joist sizes.

  10. #10
    Correct me if I'm wrong, but there's no difference in sizing my beams, joists, etc. for a free-standing deck compared to one connected to the house. I might have to add bracing to stiffen it for lateral loading.

    Right?

    BTW, my deck height is 32" at the deck surface.

  11. #11
    Join Date
    Oct 2006
    Location
    Mazon, Il
    Posts
    375
    Correct. The load of your spans will remain the same. You'll just be running them in different directions.

  12. #12
    Whoa - I must be missing something here. Simple framing will tell you that all you have to do is run your headers perpendicular to your house. Better yet is to run your decking at a 45 degree angle to your house. It adds a lot more strength, but you do use about 15 % more material.
    I don't know if you have any Menards Lumber Supply in your area, but if you do they have a computerized kiosk and you can do your own layout free of charge, its very simple and it will give you a materials list also.
    Or try your local lumber supplier.
    Building decks is alot of fun! Good Luck.

  13. #13
    Guy - you got me thinkin (and it hurts a little) so I googled decks because I figured there had to be info on posts and beams. Jackpot - go to decks.com and they have a user freindly calculator to size post, beams, decking, etc.
    Check it out, I hope it helps you out.

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