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  1. #1
    Join Date
    Dec 2009
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    2

    Default Deck Beam Design Requirement Question

    I'm getting ready to build a deck. It will be 20' wide (attached to a ledger board) x 16' deep with 2 beams under it. There will be a beam at 7' from the house and a beam at 14' from the house. There will be a 2' overhang. It will be 8' high and I plan to park 2 cars under it. With that requirement I plan to use a 24 footer at 7' and a 26 footer at 14' with no center posts so there will not be anything to hit with a car! I have 3 questions:

    1. Having looked into Rosboro Treated Glulams, what size beams are needed with a code requirement of 40 lb live and 10 lb dead (50 lbs. per sq. ft.)and an Upstate New York location.

    2. Due to the high cost of Treated Glulams, could I build up my own 2x12 pressure treated southern pine beams that would be strong enough to do the job, how big would they have to be, and would they be cost effective?

    3. How about steel beams? What size and how do they compare in price to the other options?

    Thanks

  2. #2
    Join Date
    Oct 2009
    Location
    KS
    Posts
    19

    Default Re: Deck Beam Design Requirement Question

    The questions regarding size of the beams are likely going to be determined by local codes. I'd imagine you'll need a permit, and they'll likely ask for you plans. Most locals will assist you in providing those codes, and may also require an inspection.

    I don't believe that 1 2x12 will bear the load your talking about. You may be able to create your own beams with multiple 2x12's, again a code question.

    Many communities have adopted "national" codes, but other still have their own. Look on local websites, or contact your local codes department regarding specifics.

  3. #3
    Join Date
    Dec 2009
    Posts
    2

    Default Re: Deck Beam Design Requirement Question

    Already pulled a permit and Yes they are going to inspect it. They gave me a 40lb. live-10lb. dead load (50lb./sq. ft. total)requirement. They are not requiring a drawing as the structure is readily viewable upon inspection. I, of course, want to build it right. I just need to know the specifics I enumerated in the original post. Also on the question of a beam made of 2x12's I wasn't thinking 1 2x12 would do it. I'm asking how many, if bolted together, would it take to get the same job done as a glulam? (By the way, a 5-7/16" x 16" Rosboro Treated Glulam looks like it will carry the load when used for both members)

    Any comments?

  4. #4
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Deck Beam Design Requirement Question

    Quote Originally Posted by loudi View Post
    I'm getting ready to build a deck. It will be 20' wide (attached to a ledger board) x 16' deep with 2 beams under it. There will be a beam at 7' from the house and a beam at 14' from the house. There will be a 2' overhang. It will be 8' high and I plan to park 2 cars under it. With that requirement I plan to use a 24 footer at 7' and a 26 footer at 14' with no center posts so there will not be anything to hit with a car! I have 3 questions:

    1. Having looked into Rosboro Treated Glulams, what size beams are needed with a code requirement of 40 lb live and 10 lb dead (50 lbs. per sq. ft.)and an Upstate New York location.

    2. Due to the high cost of Treated Glulams, could I build up my own 2x12 pressure treated southern pine beams that would be strong enough to do the job, how big would they have to be, and would they be cost effective?

    3. How about steel beams? What size and how do they compare in price to the other options?

    Thanks
    Quote Originally Posted by loudi View Post
    Already pulled a permit and Yes they are going to inspect it. They gave me a 40lb. live-10lb. dead load (50lb./sq. ft. total)requirement. They are not requiring a drawing as the structure is readily viewable upon inspection. I, of course, want to build it right. I just need to know the specifics I enumerated in the original post. Also on the question of a beam made of 2x12's I wasn't thinking 1 2x12 would do it. I'm asking how many, if bolted together, would it take to get the same job done as a glulam? (By the way, a 5-7/16" x 16" Rosboro Treated Glulam looks like it will carry the load when used for both members)

    Any comments?
    A 20 ft unsupported beam ------ no way you will do it with 2x12 dimensional lumber. Quite frankly I'm surprised your local muncipal building department isn't requiring drawings based on your proposed deck.
    For that kind of free span you should be having an engineer approve how and what material can be used ---- steel being one.
    The other thing that comes to mind will be the footings ---- are they not required to be in the ground below the frost line?
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
    Join Date
    Sep 2009
    Location
    florida
    Posts
    598

    Default Re: Deck Beam Design Requirement Question

    You need to provide more info before any loads can be calculated. Joist size, what type of decking,are there any railings on the deck above.If so how high and the size material being used.
    It amazes me also the building dept is going to issue a permit without approved drawings/spec's....
    Gizmo

    Cut it 3 times & it's still to short.
    Inventor of the Miter Master Plus.

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  6. #6
    Join Date
    Feb 2008
    Posts
    69

    Default Re: Deck Beam Design Requirement Question

    Depending where you are located, I would go to your local Menards store, and do the deck design on their designing machine. The printout will show you the necessary materials, and sizes for all parts of the deck. Two years ago, when I built a deck, I designed it on the Menards machine, and, Bingo, out came the list of materials, with all the necessary size requirements.

    I will also agree that the footings should be below frost level, and of sufficient diameter to support the load. Once again, the design machine will give the recommended sizes, spacing, and all specs needed.

    Good luck. and enjoy your holidays.

    woodworker08@gmail.com

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