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Thread: Minimum Beam Size for deck load?

  1. #1
    Associate Engineer
    Join Date
    Apr 2021
    Posts
    1

    Minimum Beam Size for deck load?

    For the lack of a better term, I am ignorant in regards to steel. Whenever, I have used it, I have consulted a structural eng. friend and paid him whatever he asked. However, he is going through chemo, so I cannot even consider bothering him right now.


    I understand the reluctance to giving advice in regards to beams that will support lives, so let me preface this by saying this is for a deck that will sit no more than 22" above grade.


    I am building a 29' x 24' deck which will attach via ledger board to a house (29' side). The existing patio in that space has a 29' x 14' covered porch with patio pavers at grade. The porch, which I built 10 years ago, is solid as a rock, but the pavers ( I didn't have anything to do with) are a mess. They wish to tear down the covered porch and build a raised deck so it is more walk out from their kitchen.


    I am hoping to reuse the helical piers I had installed 10 years ago. I still have the engineering from their install which indicate they will each supports loads above 35,000 lbs. per pier. I think they will work fine for supporting a middle beam for my 24' deep deck. In addition, using these will be much easier than trying to navigate the gas, electrical, and water lines that are there. I will be adding piers for the far end of the deck, but the middle beams what I have questions about.


    The 3 helical piers are 12 from the house, with a 13 oc span between them. They have a 6" x 6" plate that the current porch posts sit and they are about 4" above grade. I much prefer to have joists sit atop beams when possible, so I would like to place my center beam for the deck on these piers. An issue I have is that wooden beams would need to be 3 ply 2x12 lumber to support the load. That 12 height coupled with the 10 height of the joists puts me a little high . Thus steel.


    I hoping someone could tell me what steel beam I could use that is 6 or shorter to be my middle beam for this deck. I did a load calc for the piers this would set on and came up with right around 30,000 lbs based on a SUPER HYPER aggressive 100 lbs. sq. ft load. Denver does NOT require this much, but rather only 40, but I do like to go overkill. The load would be mostly uniform across the beam(s). Denver does not even require any engineering stamps of building permit for this deck as it is below 30 with not roof.


    Again, I am just ignorant about steel limits. I assume this is would be a pretty light load for a steel beam, but I have no idea. Thought I would try some input online overnight until I can get to making calls Thursday.


    Please let me know your thoughts and if you have any question.
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    Last edited by hweddle; 04-22-2021 at 12:03 PM. Reason: add pictures

  2. #2
    Senior Engineer
    Join Date
    Apr 2021
    Posts
    37
    The beams support the joists and transfer the load from the deck onto the posts and ledger. The minimum beam size is a 4-by-6 made from two, 2-by-6 planks

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